transmission issue troubleshooting

[uhlhazard]

Hello I started doing tuning just a few weeks back. I'm realizing the learning curve especially with my 94 4.3 cpi engine/code and sticking with the stock chip just datalogging for now.

Anyways yesterday I noticed some odd transmission behavior. Light throttle in 3rd at 25-30mph the trans jumps back into 2. Seems like if you give it a little fuel it shifts gears really quickly. I went around the block and made the attached xdl. Anyone familiar with this issue? I checked the trans fluid and it was at the top of the cold mark @ 190* fluid temp. I have a deep sump pan/filter from a late model 4l60e so I'm doubting this is due to a low fluid condition despite it being slightly low.

I recently had a code 42 "Ignition Error" blink the service engine soon light on and off so I'm hoping I can blame the distributor and be on my way. Can anyone make heads or tails of my datalog?

This is all on a 1994 GMC T15 Jimmy with a 4.3 Vortec/4l60e

[uhlhazard]

I noticed the speedometer on playback was really jumpy so I went out and swapped out the drac with one I have on-hand. Seems the problem has disappeared.

I did a 2nd datalog and tried my best to get a repeat of the trans issues. I replayed that recording and got similar speedometer jumping around. I just recently replaced my VSS in the tcase with another from the JY. I certainly hope these failures are not connected!

[buddrow]

Glad to hear you fixed it. Those pesky DRAC modules will get you every time lol.

Buddrow

[uhlhazard]

Thanks Buddrow. My first time dealing with a DRAC I thought it was a transmission computer until a few weeks ago reading a lot of amazing info on these boards.

Will confirm on a longer trip tomorrow and post results incase someone is having a similar issue googling down the road.

[uhlhazard]

Took a 2 mile trip north and found the issue still persists. Going to swap out my vss with wifey's and see if I'm killing them or if I have a wiring problem. If I put the trans in 2 via shifter I get zero shifting craziness so I believe that isolates the hydraulic system and points towards electrical.

[buddrow]

Always check the wiring/connecter at the sensor. On GM espesically, it is common for the insulation to degrade and allow the vss wires to contact each other and cancel out the signal.

Buddrow

[uhlhazard]

I got on my back in the dirt yesterday and gave it a visual inspection. It doesn't have any obvious issues and I always make sure my wires are inside good loom. If the next series of tests fails I'll be testing the wiring via my fluke. Will report findings here asap.

Theres only 1 thing I hate more than finding a bad wire in a harness, and thats PLUMBING!

Thanks for the help!

[buddrow]

You can check the incoming signal to the drac as ac volts and the output at the drac, a scope is good here but an analog meter may work as well to check for pulses out. If the readings are solid, check the drac out at the pcm. If you can log data you should be able to see the actual loss of signal.

Buddrow

[uhlhazard]

I tested without my autoprom connected which made no change whatseover. I then tested a second time with my cruise module unplugged and the same issues persist.

Next will be to swap with wifes vss. If that works I gotta figure out if I'm destroying vss or if cooincidently 2 of them have weirded out.

[uhlhazard]

So I didn't borrow the wifes because she has the only running vehicle on the ranch right now. Talking to my brother and he has a np241 in one of his project trucks. I go SWEET, I NEED A VSS. Tossed it in and the trucks running and shifting awesome. No drama. Attached is a log of a test drive with everything spot-on.

Thanks for yoru help Buddrow. What are the odds I'd have 2 bad vss? Will post longterm conclusion later. All this np241 research got me wanting to convert to an np243 because I like my electronic shifting. The 6 pinion planetary and the wider chain is pretty sweet too!

[uhlhazard]

Thread shift. Np233 to np243 upgrade would be a pretty simple swap with my 1" body lift. The fundamental limiting factor is my vacuum controlled front diff actuator. The np24x uses an electronic switch in every application I've seen therefore not worth the trouble converting the front diff to electronic actuation.

Further research concludes that my np233 is probably an np233HD evidently up to 1994 and possibly 95.5 the np233 got the 1.25" wide chain and 4-6 pinion planetary. compared to the normal 1" wide chain with 3 pinion planetary. Good times indeed!

[kevinvinv]

I have a question on transmission issues in general. Do the 4L60's post trouble codes that aren't readily seen when you scan out the engine codes? I also am wondering what the "trans" tuner pro RT files are for? Is there a different datastream or something that comes from the trans? noob.

Thanks.

[buddrow]

Kevin,

The trans codes generally will not set the check engine light but should, in OBD1 pcms, display trouble codes along with the engine codes.

The transmission parameters in the xdf are used to "tune" different aspects of trans operation just as the engine parameters do for the engine.

Buddrow

[kevinvinv]

My scanner tells me I have an "ODM Failure" from the trans. Cant seem to find out what this is. This is a 94 Chevy. I thought I'd try to hook up TunerPro with the trans xdf to see if it provided any more info... thoughts?

[buddrow]

Are you sure is isn't QDM failure? That would be a Quad Driver Module which could be a bad solenoid, wire, or pcm.

Buddrow

[kevinvinv]

Yes! You are right... it says QDM Failure... I thought it was an O not a Q.
I am getting QDM Failure 2 and SHIFT A FAILURE and SHIFT B FAILURE

This is according to my old scanner.

[buddrow]

That is likely a loss of power to the trans itself, usually it throws TCC code as well but not always. Check pin E at the trans connector as well as the trans fuse. I can dig up a photo of the harness connector but it'll be later this evening. There is always google though. :)

Buddrow

[kevinvinv]

OK- this is interesting. I am pretty concerned here as this is a sweet tranny and I am hoping it isnt a serious problem... If you have a photo- great... I'll try to google it too. Thanks man!

[buddrow]

Its not a mechanical problem with the trans so rest assured. If its throwing QDM code its usually a loss of power. Has the trans been removed/installed recently? Lemme see if I can dig up a pic real quick for u.

Buddrow

[uhlhazard]

Do a test and see if your motor mounts are broken. On the s series the 4.3 motor mounts are poorly designed with no interlock. When the rubber fails from abuse/age/heat it just separates nad lets the motor freely flop about. If you have broken motor mounts you might have some damaged wiring/sensor/connectors.

[kevinvinv]

Well... the trans has been in and out a few times... and battery power removed numerous times... so you think maybe it is a "false code" or something like that?

Here is my symptom... pretty weird:

Drive down the highway at 60MPH in overdrive and let off the gas (level road).
truck seems to "not coast too well" (drag)
Shift the lever down to 2nd gear - foot still off the gas
truck begins to coast better... like it is actually in neutral or something
rev the engine up to 2500RPM or so briefly... SLAM- the trans shifts into 2nd now (finally).

Ever hear of something like that?

[uhlhazard]

Yeah, sounds like hydraulic issues. There shouldn't be any "slam" but honestly taking a ride experience, turning that data into words and hoping the guy on the other end comprehends what really happened to you is a real challenge.

Find yourself a good trans guy or do like me and spend countless hours reading. Good rebuilding books, and buy transmission fluid by the 5 gallon bucket. I have one on my bench that came in with no 1/2. I rebuilt her, installed it she has R 1/2 no 3 and 4. Damn does it run good for 1/2 though. I'm completely confused as to whats wrong and have a list of parts and tools to buy to get her reinstalled and tested. Of course it's on an awd bravada that takes twice as long to install!

So yeah, slushboxes are very complex. Good luck man!

[buddrow]

Kevin,

When you pull the trans into 2nd at 60 with your foot off the gas the trans should freewheel, when you bring the rpm up to 2500 the trans catches and will pull you into 2nd gear giving you the "slam" you feel. The "drag you feel at 60 can be interpreted a few ways and without actually feeling it I cant say but it sounds like the trans is operating correctly in that particular situation.

uhlhazard,

No 3/4 is likely the 3/4 clutch burnt or a leak in the input drum seals. Did you install new teflon seals and did you use the solid(one-piece) seals or the split(scarf cut) seals on the input shaft?

Buddrow

[uhlhazard]

I replaced everything, used one piece seals on the input shaft. it just free wheeled after 2nd gear. On the initial test drive it did have 3/4 albeit incredibly poorly for a few seconds then quit altogether.

So when you are doing 60 and put the trans in 2nd with no throttle, the trans is effectively decoupled from the engine? Will have to test that.

[kevinvinv]

Maybe a little clarification?

Something seems weird. Are you saying that when you down shift... it doesnt actually downshift? And that is normal? I've never seen that before. If I am doing 60, foot off gas, and downshift to 2... I expect it to immediatly down-shift... but you say no? Am I understanding everything here? Thanks!! Very interested and curious!!

[uhlhazard]

Yeah Buddrow is saying what you are experiencing is normal.

[buddrow]

Yes, it is normal. It is designed so that it doesn't over-rev the engine on an "accidental" manual downshift to 2nd or 1st. It will engage at a lower mph but "overruns" at higher speeds.

When it "shifts" to third and it freewheels/engine rpm spins up if you keep your foot on the gas then the 3-4 is burnt up. The 3-4 clutch has to be engaged for 4th gear. The 3-4 clutch is on in 3rd and 4th, main difference is that in 4th the 2-4 band is applied. If your vehicle has a MAF then clean or replace the MAF as it is a main cause for failure of the 3-4 clutch as is low fluid level, a scored/damaged pump stator, 4th accumulator piston pin being worn. In either case it will require removal of the trans for inspection of the 3-4 clutch pack and associated parts.

Buddrow

[uhlhazard]

Buddrow I wish you were a little further south. I've been dying to find a local trans guy that will teach me. Everyone I've met thus far is more of a "I buy remans and install them" type service man.

I'll bear that in mind. Shes completely disassembled on my bench and I can't find anything visually wrong with her. My 3rd rebuild and it's very frustrating indeed!

[buddrow]

Are the 3-4 clutches burnt? Did you disassemble the valve body? If so its possible to install a valve in the wrong direction. I am more than willing to instruct you on how to properly rebuild any trans you want to get in to. :) Its a little bit like a long distance relationship though lol.

How far south are you?

Buddrow

[uhlhazard]

After the 3/4 failed I bought and installed a reman valve body from Shift Rite Transmissions.

3/4 clutches look new. I haven't torn the valve body apart since nothing changed after the install regarding 3/4. I'm folliwing the atra book on rebuilding this one. Last time I used the atsg and felt it's documentation lacking plus I got it from the library and that prohibits the level of procrastination I like to apply when soaked in trans fluid.

Ooh and the Bravada has no MAF, shes a 4.3 cpi just like my Jimmy. I pulled the engine and did a once over since I had the trans/tcase out. Engine runs fantastic to about 72mph when the trans goes into neutral gear instead of 3rd haha

[kevinvinv]

uhlhazard, I feel your pain. I had to rebuild my 454 twice in a row... never found the problem... just changed a bunch of parts out and re-did it all... very frustrating.

buddrow, Not sure... I just have never had that sort of behavior before. I mean... if this is how all tranny's worked then how would your average person down shift going down a mountain? In my case, if I do that, downshift going down the mountain... the freaking rig speeds up (coasts faster)!!! I mean - I've driven a lot of mountains in a lot of cars and never had this happen. :)

[buddrow]

Does it not try to shift until 72mph? It should shift into 3rd under light throttle at about 25mph give or take a few mph.

Need to perform circuit integrity checks using compressed air. Assemble the input drum(clutched installed), and pump. Place the pump with the converter seal facing down towards bench, insert the input drum into the pump with all washers/bearings in place. Hopefully the pump is emptied of fluid :).

You can leave out the sprag for this test. Apply air pressure via air gun to the feed holes in the pump. Moving from one hole to the next(some holes are not associated with the input drum) you should see and hear each clutch pack apply. You should be able to see the coast/overrun clutch(bottom), the forward clutch(middle), and the 3-4 clutch apply by applying air to different holes in the pump. I dont have a pic of which holes are which so just trial and error.

If you never see the 3-4 apply then you have a massive hydraulic leak in either the pump(not likely but possibly the stator tube) or the input drum. Inspect all seals on the input shaft for any signs of distortion or damage. Also disassemble the input housing removing all clutch packs/pistons. The last out/first in piston is the 3-4 apply piston. Is it a bonded/one piece design or does it have replaceable lip seals? Replace any damaged seals.

If all that checks out ok make sure you have all 7(seven) checkballs installed in the correct spots in the valvebody, should be a chackball location chart in the rebuild kit as well as the ATRA book. A missing checkball could also cause various issues. Time to check the valves in the valvebody for free movement in their bores. Be careful not to nick or damage the valves as that can cause the valve to stick.

If all that checks out, reassemble the transmission except for the valvebody and seperator plate. If you have a long skinny air gun then you can apply air to the input and reverse input circuits ad listen for a "clunk" type sound indicating that each clutch has applied. You can use a paper towel or even a shop rag as a "seal" on the tip of your air gun The feed holes are located at the front(pump end) of the worm tracks in the case. If you look you will see the roughly 1/4 inch holes placed parallel to the case surface. A few of the holes you will hear "hissin" which is normal, but you should hear 4 clutch packs apply, reverse input, overrun, forward, and 3-4. if you don't hear all 4 then you may have forgotten the pump gasket :).

You never mentioned how far south you were.

Buddrow

[buddrow]

Kevin,

this behavior is inherent in several transmissions. When in 4th gear there is no engine braking due to the overrun clutch overrunning or not being applied. It is applied in 1-3 gears to aid in engine braking, effectively using the engine to help slow the vehicle. When coasting downhill, downshift to third and you will feel the vehicle start to drag and engine speed increase, same thing for second and first gears depending on vehicle speed though I wouldn't recommend speeds above ~35mph or so for 2nd and ~25 for 1st.

Now, take all this info with a grain of salt as not all transmissions operate the same during engine braking, it's just a generalization.

Buddrow

[kevinvinv]

Buddrow, thanks for helping both of us, and uhlhazzard, I am sorry if I hijacked your thread a little... tell me to butt out if need be :)

I paid a little more attention on the way home tonight. Here is what I notice,

4L65E

4th gear, cruising at 60MPH let off gas.... engine braking happens (doesn't coast very well) - RPM stays up a little as the engine is dragging the truck down
Shift down to 3rd gear (normal "drive") -- engine RPM goes DOWN and the truck starts coasting much better... like it is in Neutral
gently rev the motor- up to 1500 or so... yeah- it seems like it is in Neutral.... can rev up to 1500 and down all day.. seems in neutral...
rev the motor higher to 2500, the trans shifts finally into 3rd and engine braking occurs.

If you've got the patience to comment on this sequence... I'd sure appreciate it. If you still think it is normal.... just let me know :)

Thanks man!!

[buddrow]

It almost sounds like the sprag is installed upside down but that would be noticeable as you would have to place the shifter into 3rd or lower to take off from a stop.

[uhlhazard]

Buddrow: Awesome info. I believe you are referring to "air checking" the drum assy. I'll get er done tomorrow. You motivated me to clean up my shop so now I got an np241 I just went through for craigslist!

The molded vs lip seal piston you speak of. I believe you are referring to a piston that my new manual is saying to trash the lip seal aluminum one for a steel molded piston. Evidently those can have invisible cracks and cause crossleaks. That part is what stopped me from continuing the project. This transmission keeps soaking up $$.

After my first rebuild when the trans goes for 3rd it just freewheels. If I romp on it from say 40mph , she slams into 2nd and whoops it... till she redlines at I think 72mph. If you let off of the gas the engine drops to idle despite doing 70mph. Once you slow down to say 30 or so it grabs 2 and is back to normal. (its a 3.73 geared 94 bravada with 235/75/15's and a very good running 4.3 cpi)

Trans history: The old trans came to me with no 1/2. Just reverse. They already did the solenoids thinking it was that. (I can't ever seem to have a failure that's that simple)
I tore it out of the vehicle, made a 2 page list of broken stuff on the truck. The motor mounts on 4.3's are garbage and the prop shaft was slamming into the body. Had a good 4" diameter punch under the driver seat.
Dropped the pan to find a TON of clutch material. Started puling the pump off and that is where the drama began. Once I was inside of the drum there was black burn marks everywhere.
I believe it is called the "forward sprag" the little one. It would spin both directions, had slack and the clutches teeth on the sprag were rounded off and warped. The inner went in and the outer went way out, say 1/2 an inch.
The 3/4 clutches did look good but burned (all clutches/steels were replaced) in fact nearly all of the internals were replaced with a 700r4 gm goodwrench. This definitely became a frankenstein project.

I'm in Willis, TX so a good 5+ hours from ya! Hell the goodwrench trans came from oklahoma. Guy swore up and down it was for a 94. i get there and said "nah, its a 92 or older". He gave it me much cheaper for wasting my time.
E MEANS ELECTRONIC!!!

Anyways Kevin you aren't threadjacking anymore than I am. Ultimately this is just us 2 noobies getting some valuable intel from our superior on transmission issues.
I towed a trailer across town today for about 2 hours and a few times above 60mph I dropped into 2 and it doesn't slam into gear like I thought it did, was gentle and the speed does drop rapidly.

Kevin, can you datalog driving in your trans? I am certain watching your datalog through all 4 gears I can at least point you in the right direction.

[kevinvinv]

It almost sounds like the sprag is installed upside down but that would be noticeable as you would have to place the shifter into 3rd or lower to take off from a stop.


Taking off from a stop and any upshifting in general is basically perfect... just the down shifting is messed up (IMO).

[kevinvinv]

uhlhazzard,

I can datalog with TunerPro RT. What do you think would be good... just log the scenario I described? Maybe I can get that done in a day or so...

[uhlhazard]

A 10 minute drive going through all the gears under normal driving and possibly some WOT passes would be awesome. I'd like to see your 1-2 and 2-3 shift times and when you go into lockup how it holds.

[buddrow]

Kevin, get a log, as short as possible but with the problem happening and Ill have a look. Need to see if the pcm is commanding the downshift.

uhlhazard,

Willis, TX is a bit more than a 5 hour dive for me. I'm just north of Tulsa, OK and its about a 4.5 hour drive to Dallas from my house. I'll be in Dallas briefly not this weekend but the following weekend helping my mother move back to OK. If I wasn't flying down I'd just build you a trans and meet you in Dallas. :)

As for using the aluminum piston Ive only seen a few cracked in the 20ish years Ive been doing trans work and it would likely go into 3rd but maybe slip under load, if it air checks it should be ok. You can also air check the drum apart from the pump using the feed holes in the input shaft. The swapping of the internals shouldn't be a problem unless there is a slight mismatch in the pump/input shaft feed holes. If it's an early 4l60e it should be ok, I'll look in my parts book in a bit and see to be sure.

NOTE: When air checking always remember safety first and keep your head away from potentially flying parts, i.e. clutch plates, etc.

[uhlhazard]

I read to set the air regulator to 40psi to reduce the flying parts phenomonon. Thanks a ton! Ill check the feed holes. From everything i can see the r4 is a 92/93 and the bravada is a 94. Both caees have the 4 bolt output instead of the newer 6 bolt. I gave a friend of mine the valve body which got his suburban up and going. He was thrilled. Will report back asap!

[buddrow]

The 6 bolt tail housing didn't show up until the 3 piece case with the bolt on bell housing on the later units. 93 was a transition year. early production units were 700R4 while later production were 4L60E's. Some 92 cars got the 4L60E. But you obviously know how to tell the difference. :)

Buddrow

[uhlhazard]

Hey Buddrow you might know the quick/dirty answer for this: My brother gave me an np241 tcase.

History: He bought it and a transmission that had 20k after reman on them from goodwrench. He just needed the trans so he kept his tcase.

Research: I googled the difference and it's a pretty sweet unit. It has a higher sustained tq value from the engine side than my np233. Reading online the 241 has a 6 pinion planetary, a 1.25" wide chain, and a stronger 4 series case. I have an np241-4l60e mount/adapter from my brothers old trans and was wondering if I could upgrade to the 4 series case.

Results: After some mocking up I realized that the largest issue is the 4 series doesn't seem to have a vacuum actuated front diff like my S-series and I don't want to convert over to electric. If I can find a vacuum switch for the 4 series tcase, then I can proceed with the mod. That doesn't account for yolk differences and shift solenoids either but gotta start somewhere.

To consolidate my overly verbose question: Is there a vacuum switch application for the 4 series np transfer case that you are aware of?

[kevinvinv]

Kevin, get a log, as short as possible but with the problem happening and Ill have a look. Need to see if the pcm is commanding the downshift.



Buddrow, on the log file, do I need to log it with a "trans" adx file or does that matter? - I assume it does matter.... There are two different trans adx files if so... so I am not sure which one to use really. This is for $0D 6395 PCM. I'll try to figure it out but in case you have a comment off-hand... thought I'd ask.

[buddrow]

Hmm, I cant think of any right now but it's prolly because my brain is mush from writing code all day. You could try installing the vacuum switch from the 233 into the electric switch(similar position on tcase) spot on the 241 and see if that nets u the results u need. The switch on the 241 turns on the light for 4HI/4LO on the dash/console. Both switches are basically the same aside from one being a vacuum control switch and the other an electric switch. It's worth a shot.

Buddrow

[uhlhazard]

The vacuum switch has a ball that protrudes just beneath the surface of the 233 tcase, the electronic switch protrudes a good 3/8 inch beneath. The threads are the same but after looking inside of the 241, the arm that hits the switch would never reach it.

There is almost no information available online for the swap I'm looking for so I'm guessing its not done or there is some fundamental issue. I know a lot of guys hate electronic tcases and vacuum actuators. I like them personally and will stick with the 233 if the 241 swap won't work.

Ooh I also forgot to mention. I read on zr2.net that you can swap in the 6 pinion planetary from the 4 series into a 3 series BUT evidently they changed the design of the gears 95/on and my 4 series is a 96 with my 3 series a 94 so I didn't want to risk it.

[buddrow]

Buddrow, on the log file, do I need to log it with a "trans" adx file or does that matter? - I assume it does matter.... There are two different trans adx files if so... so I am not sure which one to use really. This is for $0D 6395 PCM. I'll try to figure it out but in case you have a comment off-hand... thought I'd ask.

Kevin,

Log with the trans adx. http://www.tunerpro.net/download/datastreams/GM/A218_0D_Trans1_v250.adx

Buddrow

[buddrow]

The vacuum switch has a ball that protrudes just beneath the surface of the 233 tcase, the electronic switch protrudes a good 3/8 inch beneath. The threads are the same but after looking inside of the 241, the arm that hits the switch would never reach it.

There is almost no information available online for the swap I'm looking for so I'm guessing its not done or there is some fundamental issue. I know a lot of guys hate electronic tcases and vacuum actuators. I like them personally and will stick with the 233 if the 241 swap won't work.

Ooh I also forgot to mention. I read on zr2.net that you can swap in the 6 pinion planetary from the 4 series into a 3 series BUT evidently they changed the design of the gears 95/on and my 4 series is a 96 with my 3 series a 94 so I didn't want to risk it.

Look at the full size dodge trucks, they used vacuum acutated diffs. maybe a vac switch from one will have enough reach. Also, check the driveshaft yoke and make sure it is the same spline as well. Some were 27 spline, some 31 spline.

Buddrow

[kevinvinv]

Hey Buddrow, sounds like you have had a long day. What were you coding for? Curious.

Attached is my log.

Basically this is the sequence:

Truck stopped,
accelerate up to 4th gear,
TCC Locks
Cruise for a few seconds,
Let off gas (note TPS)
shift to D3
RPM DECREASES slightly ??
Now shift do D2
RPM stays low
Slowly pulse the throttle (note RPM increasing and decreasing with TPS as I gently pump the pedal)
Finally give the pedal a pretty good press and then let off
You will notice the RPM stays high but the TPS goes back low again... indicating that the tranny is now engine braking.

I cant seem to find what field shows if the PCM is commanding this behavior or not... sure welcome your thoughts... later

[buddrow]

Kevin, Looked at your log after making a new dash in the adx with a few pertinent parameters. Transmission is doing what its told to do. Ive attached the adx so you can see what I'm seeing. Open the Diag Dash(drop down menu upper left corner of Main dash).

While playing back the log, watch the current gear, it is the commanded gear from the pcm. Notice the "Drive 2", Drive 3", & "Drive 4" params, this is position of the shift lever.

Buddrow

[kevinvinv]

buddrow, thanks for that. Cant look at it until tonight. Can I clarify something?

The "current gear" -- is that as reported by the transmission then? I do think I recall seeing that "current gear" followed my shift lever position nicely. It is just that when I went to D2, the dang thing didn't shift down until I rev'd the motor up to about 2500RPM. You can see that in my original log if you watch the RPM towards the end. When it goes up and stays up... that is b/c the engine braking started to happen.

Looking forward to checking out your adx tonight.

BTW- do you know how I can find out which things the QDM controls in this PCM (6395) ? I still am worried b/c the datastream is showing QDM faults (although there is no trouble code posted).

[buddrow]

Kevin,

I'm not sure, as 1project2many and Billy Graves posted, what they actually connect to or where. All I know from my exp with the code is that it seemed to always correlate to a loss of power/short to ground in the circuit. It may be time to find a good used pcm to try out if the circuits from the pcm to the trans check out OK. I think the last time I saw a ODM code was in an early 90's front wheel drive car but that's been a minute lol.

As for "my" adx, I just used the existing adx and added another dash screen with only the items I would use in such a case as yours to demonstrate how the computer shows the commanded gear versus what the trans is actually doing. The current gear status is the commanded gear from the pcm, When you pull the manual lever down to 2nd above a certain mph it will the trans will freewheel until a certain rpm is reached and then it "latches up" into that gear. same for first. It does this to prevent overrevving the engine.

Buddrow

[kevinvinv]

Cool... thanks... will look more tonight when I get a minute.

One question... lets say I want to probe the wires in the trans harness. Is that do-able with a meter or a test light? I know the pins are labeled like 1-2 clutch and 3-4 clutch or somthing like that... how do I make sense of this? Is it something like when the line is pulled to ground, the shift happens or something?

I called the place I got the tranny from today over in Chicago- he thinks the overrun clutch drum is bad... but before I pull this sucker out for the second time- I want to make sure there is nothing electrical jacked up....

Thanks!

[lionelhutz]

I can't see the solenoids being bad if it's up-shifting fine. The 4L60e uses 2 solenoids to select the 4 forward gears. Solenoid A is energized for 1st and 4th and solenoid B is energized for 1st and 2nd. If you lose solenoid A you can only get 2nd and 3rd gears. If you lose solenoid B you can only get 3rd and 4th gears.

If you unplugged the transmission connector or blew the transmission fuse it would default to 3rd without any power to the solenoids. Kind of a limp-home mode.

The transmission has power applied to the solenoids and then the PCM grounds the solenoid to complete the circuit.

[buddrow]

I can't see the solenoids being bad if it's up-shifting fine. The 4L60e uses 2 solenoids to select the 4 forward gears. Solenoid A is energized for 1st and 4th and solenoid B is energized for 1st and 2nd. If you lose solenoid A you can only get 2nd and 3rd gears. If you lose solenoid B you can only get 3rd and 4th gears.

If you unplugged the transmission connector or blew the transmission fuse it would default to 3rd without any power to the solenoids. Kind of a limp-home mode.

The transmission has power applied to the solenoids and then the PCM grounds the solenoid to complete the circuit.


If solenoid B fails you get 1st and 4th, Solenoid A fails, 2nd and 3rd only. Sequence from 1st thru 4th Solenoid A/B = on/on, off/on, off/off, on/off.

You don't see the overrun clutch fail very often, like maybe 1/1000 units and it's usually accompanied by the forward clutch and input sprag failure as well.

Buddrow

[buddrow]

Cool... thanks... will look more tonight when I get a minute.

One question... lets say I want to probe the wires in the trans harness. Is that do-able with a meter or a test light? I know the pins are labeled like 1-2 clutch and 3-4 clutch or somthing like that... how do I make sense of this? Is it something like when the line is pulled to ground, the shift happens or something?

I called the place I got the tranny from today over in Chicago- he thinks the overrun clutch drum is bad... but before I pull this sucker out for the second time- I want to make sure there is nothing electrical jacked up....

Thanks!

Yes you can probe the wires in the trans harness with either a test light or DVOM or analog meter. They aren't labelled as 1-2 or 3-4 shift but as Power, Sol A, SOL, B, TCC, TCC PWM, MPS, etc. Power wires(there are 2) are Pink or Pink/Black.

Power is supplied at Key On, pcm controls the ground circuit to the respective solenoid.

If you're in doubt as the the trans operation, take it to a reputable trans shop that does free or low cost diag. I wouldn't tell them anything other the actual problem you are concerned with. I don't trust anyone no matter how nice they seem, Ive worked around way too many crooks.

If you wanna pull it out and tear into the trans I'll walk you through the process, it's not hard.

Buddrow

[lionelhutz]

If solenoid B fails you get 1st and 4th, Solenoid A fails, 2nd and 3rd only. Sequence from 1st thru 4th Solenoid A/B = on/on, off/on, off/off, on/off.

Ummm, look at the 2 "off" gears for solenoid B - 3rd and 4th??

You get 3rd when the controller fails to energize any solenoids (goes to a limp-home mode) so 1 of the choices for both solenoids failing has to be 3rd.

[kevinvinv]

OK thanks. Where can I get a pinout of the connector at the trans end

-- strike that... I'll just find it with google. Thanks (too early for me yet!!) :)

[buddrow]

Ummm, look at the 2 "off" gears for solenoid B - 3rd and 4th??

You get 3rd when the controller fails to energize any solenoids (goes to a limp-home mode) so 1 of the choices for both solenoids failing has to be 3rd.

You are correct but, the trans will never default to 3rd and 4th, only 3rd. If sol B has failed off but sol A is still functioning you will have 1st and 4th, no 2nd or 3rd. If solenoid A fails you will have 2nd and 3rd, no 1st or 4th, since sol B is still turning on and off allowing for the gear change. If you look at the sol state chart, you will see that in 1st, both sol A and sol B are on. In 2nd, sol A if off, B is on. In 3rd, both solenoids are off, in 4th, sol A is on, sol B is off.

Not trying to get into a pissing match Lionel, just tying to clarify things a bit. I've been in the transmission sector for about 20 years, currently building a trans controller for the 4L60E, L80e, Ford AODE, E4OD, etc. I know quite well how they work. :)

Buddrow

[lionelhutz]

You're confusing the failure modes of solenoid A (fail to open vs not closing or leaking) with the failure modes of solenoid B.

If the A solenoid fails (electrical or mechanical) then you either get a 1-1-4-4 or 2-2-3-3 shift pattern depending on the failure being the solenoid failed open or failed closed.

If the B solenoid fails (electrical or mechanical) then you either get a 1-2-2-1 or 4-3-3-4 shift pattern depending on the failure being the solenoid failed open or failed closed.

If the solenoid B doesn't open (no electrical command to it) then the transmission won't select 1st or 2nd gear, with the shifter in OD (or highest gear selected).

I can read the service info directly from GM and follow the shift solenoid logic quite well. The failure of solenoid B to open (the PCM not commanding the solenoid) will not cause the transmission to only give gears 1 & 4.

The above all assumes the PCM thinks the solenoids are OK and tries to normally shift the transmission. Typically, the PCM will have circuits to detect that the shift solenoids are open circuit or don't have power applied to them.

Still, my point was that when you have the transmission in OD (or highest gear selected) it won't properly upshift through the 4 gears if the 2 main shift solenoids are not being controlled properly.

There is a 3-2 solenoid. If you're concerned about electrical issues only when downshifting to 2nd gear then that would be the place to focus. As I understand it, this solenoid modifies the 3-4 clutch release to 2-4 band apply timing. It seems to be for PCM commanded downshifts and not manual downshifts.

The info I have says that all manual downshifts except the 2-1 are initially hydraulic and then the PCM plays catch-up with the shift solenoids.

The 2 shift solenoids are often labelled as 1-2 and 2-3. The 1-2 is the same as A and the 2-3 is the same as B.

[suffolkauto01]

4l60e likes to get check balls stuck in valvebody plate transgo makes a new plate like 20$.

[uhlhazard]

Here to bring a little sunlight and possibly laughter to you people.

Started working from the ground up on the 4l60e on my bench. Rebuild 2. Following advice from buddrow I learned that I had about 10x more clearance than required on my 3/4 clutch pack. Weeel I found a clutch plate behind my bench under my soiled rag pile used to soak up spills. I felt like a total ass after finding this. THEN it got worse. I also found a torrington bearing that goes inside of the sprag inside of the input drum. So I completely forgot to install that to begin with. Not sure how anything worked.

I'm on to issue number 3: bearing clearance. My manual calls for "no more than .003" when I have .010. The bushing was new and I have another one. I mocked up the new bushing and it's the same thickness. I tried measuring a trans we took apart that was working for hard parts. It was .010. I dunno what to say on that but I'm worried it will be an issue down the road and would love some advice. (I'm hoping I'm not told to get a new drum, I was thinking about eating dinner for the next few weeks)

The air checks (after replacing stuff) were fantastic. So I'm stuck at this pump bushing clearance issue and cannot proceed until further research.

[suffolkauto01]

listen it sounds like a valve body check tps but 4th gear is usually the valve sticking and 4th is a band 2 pull the cap at the front of trans make sure nothing broke in there

[suffolkauto01]

listen don't go crazy with those clearances i don't even check them when I rebuild 8 out of 10 times I use the trans go boost valve repair kit and I get the separator plate and put aluminum accumulator pistons all under $100 most used valve body 1 don't come with plate 2 plate is damaged. look at check balls put in plate if almost falling through no good. the make a repair kit but the upgraded plate is pre drilled if you see no crap in pan, tips is acting right trust me this is most likely your problem or the band servo is broken

[suffolkauto01]

how does the pump bushing look and torque converter does it look good?

[uhlhazard]

They both look fantastic. I'll just reuse and cross my fingers.

[suffolkauto01]

look at valve body spacer plate make sure no lip where check balls sit i mean u can take out the 1-2 2-3 give you a hard as hell shift

[uhlhazard]

I got a brand new transgo plate with my reman valve body. To hell with reusing spacer plates!

[suffolkauto01]

what about boost valve

[uhlhazard]

I ground notches on the 2nd land 3/16 inch and drilled out the valve out 1/64 iirc. They called for a #60 bit and this was just slightly smaller.

[suffolkauto01]

transgo sk 4l60e pick up this kit

[suffolkauto01]

were did you get you valve body rel co?

[uhlhazard]

Company on ebay called shift rite. So far ie had 2 from them working great.

[suffolkauto01]

How did the internals of trans look?

[suffolkauto01]

remember 4th is a band and clutch pack together band has to be adjusted right 2. how was your 1-2 shift

[uhlhazard]

The 1/2 shift was pure sex. The internals were brutal the first time around. The 2nd time it was immaculate.

[suffolkauto01]

but 2nd time u were missing parts correct?

[uhlhazard]

Yeah the first rebuild sucked with no 3 and 4. This time around I found 2 missing parts and the clutch clearances were way out of whack.
2 concerns on this build:

I have no tools to measure the selective washer that goes on the input drum so im using what it came with.

The accumulator springs and piston positioning are confusing. Im going back with what it had but im worried they are wrong. With that said, if it turns out they are wront i can always drop the pan and cprrect the issue.

[suffolkauto01]

4th gear accumulator people swap for some reason i understand the theory just don't think necessary the trans go kit tells you to do it put the spring in 1st then piston

[suffolkauto01]

again i feel for clearances the pistons have a pretty good travel I mean missing a clutch plate yea no good but I think your over thinking it Ive been building 4l60e - 700r4 since I was 13

[suffolkauto01]

http://www.transgo.com/4L60E_HD2Video.html

[uhlhazard]

I know there are tolerances I just want to have it last as long as possible.

[suffolkauto01]

i know look at video i think those are the springs you talking about did you change out all the plastic pistons just to show you how there put in any questions upload pic

[uhlhazard]

Yeah I always trash plastic pistons. Have about 10 aluminum ones with varying pin sizes I've either bought new or extracted from good cores. I think the scotch brite pad for hitting parts is a great idea too.

[suffolkauto01]

the steals always you want bite

[kevinvinv]

Interrupting a bit here....

Awhile ago I reported a lack of engine braking on my 4L60E - brand new from Finish Line Transmissions.

As a followup, I sent it back to the shop and they found that there was a problem (as suspected) with the overrun clutch hub (?) - some sort of a "leak" in the circuit I believe due to a bad seal.

They fixed it quick and shipped it back. I just got it in but haven't taken it for a ride yet... so I probably jinxed everything- but I am expecting it to be fixed now. :)