late part throttle shift 4L60E

[LeMarky Dissod]

The datalog shows the PCM commanding the shift according to the tables in the bin at 5450RpM. However, the shift is not completed until 6100RpM.
There is no slipping whatsoever in the climb through the powerband and when the shift happens, its solid with no apparent slippage or slush.
It's obviously being delayed within the transmission but when it does happen, it feels healthy.
So, I don't think I have any clutch slippage issues.

I did some research and found this thread which further helps me understand things. Look at line 5 about shift timing.
I think Ill try adjusting the the max MpH lower to see if that gets me where I want.

http://www.gearhead-efi.com/Fuel-Inj...vations-(8051)

Also, further down in that post look at line 3 in the tuning suggestions
I compared those suggestions with my bin and I think I found another potential issue with my bin. I posted the table below.
The tuner (who I'm sorry I paid) has errors there too I think.
In the 2-3 shift timing its set to 6.38 seconds.
Shouldn't that be .638 sec instead?

Attachment 16986

NEVER used a shift time higher than .750.
6.375 is the shift time for T56 .bins.

[JD1964]

I'm certainly no expert in this but I think I've got it under control with the help of everyone here, so thanks.

I made adjustments to tables which now command WOT shifts at 5000rpm. There's still a delay in the shift action but it happens between 5500 and 5800 pretty consistently. It feels much better since the engine is just below to top of the power curve. So, as far as command and action is concerned, there's a delay. However, the seat of the pants sensation gives no concerns, it feels good. That "hang time" is gone.

I saved a screen shot of the tables with the changes I made so you can criticize if you think its necessary.

I also posted a data log file of a short drive with a few WOT's including 1-2's and 2-3's. The WOT events are at #1355, 1872, 3442 and 3716. If you see anything wrong or concerning in the log, please tell me.

trans adjust completed.jpg

[JD1964]

I cant get the data log file posted. I'm not sure why it wont upload

[tayto]

try setting your shift times to 0.300

EDIT: changed number not sure if your 4L60E is stock,built, shift kit etc

[LeMarky Dissod]

I'm certainly no expert in this but I think I've got it under control with the help of everyone here, so thanks.

I made adjustments to tables which now command WOT shifts at 5000RpM.
There's still a delay in the shift action but it happens between 5500 and 5800 pretty consistently.
It feels much better since the engine is just below to top of the power curve.
So, as far as command and action is concerned, there's a delay. However, the seat of the pants sensation gives no concerns, it feels good.
That "hang time" is gone.

I saved a screen shot of the tables with the changes I made so you can criticize if you think its necessary.

Do not see where you adjusted the corresponding KickDown road speeds in MpH.
If 5000RpM turns out to be under the road speeds in your KickDown MpH table, MpH becomes the final criteria that triggers the WOT UpShift.
(I find 26" tires irksome. What is your tire size?)

With 4L60E, 3.73, & 205/65R15 (25.49" tall) @ 5000RpM:
1Up2 @ 33MpH
2Up3 @ 62MpH
3Up4 @ 101MpH

Once the TPS% exceeds KickDown Threshold, the VSS exceeds 33MpH / 62MpH / 101MpH, then the engine exceeds 5000RpM, THEN the WOT 1Up2 UpShift gets commanded and STARTS.
If the KickDown road speed thresholds are over 5000RpM, MpH becomes the final criteria that triggers the UpShift.

Errors in the speedo constants can leave you thinking your final criteria is RpM, when it's actually MpH.

[JD1964]

Ok, I’ll check out the kick down road speeds too, thanks.

Bottom line is, before the shift was too late. Good quality shift but too late. The engine was going flat s second or two before the shift. Now, it’s shifting right before the engine flattens out. Nice solid shifts and not too harsh.

[lionelhutz]

The 4L60e always seems to have a delay between the PCM deciding to shift and the shift finally occurring, even after tuned. I find I put the 1-2 shift 200-300 rpm lower than the 2-3 shift for them to actually happen around the same rpm. With the delay, the engine rpm is climbing faster in 1st so the shift needs to be done a little earlier.

[LeMarky Dissod]

The 4L60E always seems to have a delay between the PCM deciding to shift and the shift finally occurring, even after tuned. I find I put the 1-2 shift 200-300 rpm lower than the 2-3 shift for them to actually happen around the same rpm. With the delay, the engine rpm is climbing faster in 1st so the shift needs to be done a little earlier.

All the more reason to be careful with the KickDown Thresholds, both the RpMs & the MpHs.
Even GM made the 1Up2 shift 100RpM under the 2Up3 shift in the F- & Y- LT1 cars with 4L60E.

[In-Tech]

Yes, it's transport delay, it happens electronically and mechanically. Adjust to suit :)

[NomakeWan]

Thanks for that input NomakeWan,

The datalog shows the PCM commanding the shift according to the tables in the bin at 5450rpm. However, the shift is not completed until 6100. There is no slipping whatsoever in the climb through the powerband and when the shift happens, its solid with no apparent slippage or slush. It's obviously being delayed within the transmission but when it does happen, it feels healthy. So, I don't think I have any clutch slippage issues.

The story on this donor car (94 Z28) is the mother let the kid drive it and he put it in a ditch causing moderate damage to the right front corner. Thats what took the car off the road. The car sat for several years after that. When I bought the car they claimed the transmission had been rebuilt a few months before the kid wrecked it. When I pulled the engine / trans from the car I found initials and date written on the bellhousing with sharpie marker. The data coincides with the time the trans was claimed to be rebuilt. She said she knew the mechanic and he was familiar with the weakness of these transmissions and he had done stuff to improve it. She did not know exactly what so neither do I. Not to ramble but this may support my position that the transmission should be healthy internally.

I did some research and found this thread which further helps me understand things. Look at line 5 about shift timing. I think Ill try adjusting the the max MPH lower to see if that gets me where I want.

http://www.gearhead-efi.com/Fuel-Inj...vations-(8051)

Also, further down in that post look at line 3 in the tuning suggestions. I compared those suggestions with my bin and I think I found another potential issue with my bin. I posted the table below. The tuner (who I'm sorry I paid) has errors there too I think. In the 2-3 shift timing its set to 6.38 seconds. Shouldnt that be .638 sec instaed?

Attachment 16986

Just because someone claimed to build it doesn't mean it was built right. I'm not saying it was necessarily built wrong, but there are a lot of folks who claim to build 4L60Es that end up being trash. It's not a complicated transmission, but you have to actually care about your work and actually know what you're doing or it's very easy to overlook a component (or cheap out) and end up with a junk transmission not too long afterwards. Garbage in, garbage out.

Your table looks bone stock with zero modifications. I see nothing wrong with it. It doesn't appear the tuner touched it at all.

NEVER used a shift time higher than .750.
6.375 is the shift time for T56 .bins.

Nope. I have a stock '94 Corvette with a 4L60E, and this is my table:
4l60estock.jpg

Not saying you can't do better by messing with those values, but claiming they're wrong is incorrect. They're factory GM values.

[lionelhutz]

There has to be something wrong with those times, because the shift doesn't actually take 6.38 seconds and the transmission couldn't survive 6.38 second shifts at 100% throttle.

AFAIK, those times are supposed to set the shift time via a PCM calculation that modifies the line pressure to get the transmission to shift in the time specified. In other words, it is to compensate for the transmission wearing and for variations in the line pressure since the PCM doesn't actually know what the line pressure is.

[LeMarky Dissod]

I have a stock '94 Corvette with a 4L60E, and this is my table:
4l60estock.jpg

Not saying you can't do better by messing with those values, but claiming they're wrong is incorrect. They're factory GM values.

NEVER used a shift time higher than .750.
6.375 is the shift time for T56 .bins.

I'm averse to using 'I'. The 1st sentence is merely self-referential.
"6.375 is the shift time for T56 .bins" is technically correct, but it's also incomplete - my 16200891 shows the same values in the same table you pictured.

[JD1964]

Your table looks bone stock with zero modifications. I see nothing wrong with it. It doesn't appear the tuner touched it at all.

Thanks for your imput and you may remember you had helped me over at Corvette Forum with this same issue. Actually I had changed those line pressure values. I never even driven the car with the values the tuner had in. Here they are. And here is his complete bin.

tuner-line pressures.jpg

[In-Tech]

I apologize that I haven't followed this thread and others.
A rule of thumb, don't try to adjust pressure tables above 90 psi.
Almost all of the aftermarket has the table settings wrong due to changes in the valving and mid plate changes for certain "performance" vehicles. Watch the B body trans stuff for more accurate info.
The software guys at gm didn't know what the hardware guy's were doing in the valve body stuff. :( The b body guys were paying attention.

[JD1964]

Watch the B body trans stuff for more accurate info.
The software guys at gm didn't know what the hardware guy's were doing in the valve body stuff. :( The b body guys were paying attention.

Good info thanks. The b body towing bin is where I copied the pressure tables I’m now using.