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Thread: whaddaya know...another 700r4 TCC lockup thread.........

  1. #1
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    whaddaya know...another 700r4 TCC lockup thread.........

    Alright, after a year and a half, I finally took the plunge and rebuilt that spare '91 700r4 transmission I have.

    Pretty much a success and am very happy with the results of it.

    Now it's on to "re-tuning" since the transmission is running like it should and up to date, I've tuned the BIN around the crappy transmission.

    At the moment, I've been fighting with the TCC lock up.

    Now, to share what I have learned based on MY setup, which is the following:

    (DISCLAIMER: What I am sharing below is what I have learned about MY setup. I am not an expert on 700r4's, nor am I an expert on tuning.)

    1985 S-15, originally had a carbureted 2.8, now has a '93 Firebird 3.4L
    I put an Edelbrock intake on it with a Holley 390 carb.
    From there, I installed a complete TBI system from a 1988 S-10 with a 2.8L. This is the 1228062 ECM.
    I then installed 4.3L injectors along with the bigger bore throttle body.

    I then tuned the BIN file around the '85 700r4 in it with apparently worn out 3/4 gears.

    Moving on, now that I've got the freshly rebuilt r4 in, the task at hand was to figure out the TCC lockup and how to tweak the parameters as this transmission has a different lockup solenoid wiring setup than the '85.

    The '85 has just the solenoid. This solenoid was controlled via the vacuum switch through the brake switch.

    The '91 has the solenoid and a 4th gear pressure switch, which feeds the "high gear" signal to the ECM.

    My goal was to have the TCC lock and unlock completely controlled by the ECM. This was easily accomplished as I just added a wire for the run between the 4th gear pressure switch and the brake switch connection on the transmission to the ECM. Running the TCC lockup from the ECM to the transmission wasn't an issue either.

    Problem now is that since I have eliminated the vacuum switch, I needed to look at the ECM parameters for the TCC.

    Just like the 7747 ECM, the 8062 ECM has these parameters:

    Under "Scalars";
    Minimum Coolant Temp for TCC
    Lock Delay After 4-3 Shift
    Delay to lock after all other conditions met
    Speed at which TCC always locked
    3rd Gear Lock Speed
    3rd Gear Unlock Speed
    4th Gear Lock Speed
    4th Gear Unlock Speed

    Under the "Tables";
    3rd Gear Upper Limit
    3rd Gear Lower Limit
    4th Gear Upper Limit
    4th Gear Lower Limit

    Now, I was initially having an issue with the lockup with the BIN I was using, so I had to go compare BINS. What I found in the BIN that I was using was that in the 3rd/4th gear tables, the %TPS values were all set to 100. I looked at a variety other BINs and found these values varied.

    I realized then that the reason for those variations was that the BIN's with the TPS values set to 100, these were transmissions that were still using the vacuum switch to control the unlock, but yet used the ECM to lock the TCC.

    Remember, the TCC provides the GND side of the solenoid operation.

    I then copied the tables from what I can only guess is a newer BIN file.

    As a result, the TCC is locking and locking as it should when cruising, accelerating, and decelerating.

    I am currently adjusting the Delay time because I don't like the TCC lockup to occur in 3rd, and I've found that setting the Delay to lock at 4 seconds gives the transmission time to get into 4th at a cruise and lock about 45mph.

    The next goal line so to speak is to try to figure out what BIN's there are out there that is closest to my application with the TCC parameters that best suit me, but in the end, it may just end up being personal preference since I now have the ability to tweak the BIN parameters in real time.

    I will edit and add to this as I learn or remember anything of relevance to this thread.

  2. #2
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    Are you saying you put the 4th gear switch in series with the brake switch before wiring to the ECM?

    The tables in $42 are described wrong in CATS and I believe the $42 TunerPro definition file as the same description as from CATS. So, if you have a description in your definition file it just might be wrong too. The tables really work like this.
    The TCC will lock when the %TPS goes below the lower limit.
    The TCC will unlock when the %TPS goes above the upper limit.
    The TCC will remain in whatever state it is in when the %TPS is between the limits.

    Here is an example.

    Say the limits are 30% and 50% at 60mph. You were accelerating and holding about 40% throttle as you accelerated and as you reach 60mph the TCC is still unlocked. Now, you back off the throttle because you reached your cruising speed so the %TPS falls below 30%. The TCC will now lock. Once you are driving with the TCC locked you have to go above 50% TPS to unlock it again.

    I think you can come up with decent table by disabling the TCC and then driving 30mph, 40mph, 50mph and 60mph in 3rd and 4th gear and and noting what %TPS you are using at each speed to maintain a stead speed. Set the lower limit say 5% above that %TPS for each speed with the corresponding upper limit another 10% higher. Then tweak as necessary.

    Maybe you have different goals but this is what I try to achieve and doing the above should come close to achieving both of these.
    - I don't want the TCC to lock when using acceleration levels of %TPS.
    - I want the TCC to unlock quickly as I go from cruising %TPS to anything higher. The extra throttle means I want to accelerate so I want the TCC unlocked.

  3. #3
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    Sorry about the confusion, but the 4th gear switch goes to the ECM. I see above where I stated that I wired it to the high gear input and then wrote that I wired it through the brake switch.

    The latter was wrong. The correct, as it was written was the 4th gear switch is wired to the ECM.

    I'm not using the $42, I'm using the $4E.

    The tables for the 3rd and 4th gear upper and lower limits were copied from a BIN used in the 4.3l Bravada using the 1228062 ECM.

    You've posted before about the limits in a previous thread that I had started quite a while back and just read through it yesterday, but what you have written above, while the same essentially, is easier to understand than what you had written before.

    Thanks for responding with that because it does clarify how I can determine the lockup to suit my driving habits better.

  4. #4
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    - I want the TCC to unlock quickly as I go from cruising %TPS to anything higher. The extra throttle means I want to accelerate so I want the TCC unlocked.
    In many cases it's OK to leave TCC locked a bit longer. If you're just looking to maintain speed, such as on a highway that climbs a slight grade, it becomes very tiring to be unlocking TCC, accelerating above target speed, then having TCC lock again when you release throttle. The trick seems to be to balance the engine's torque output with driver preference.

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    Quote Originally Posted by 1project2many View Post
    In many cases it's OK to leave TCC locked a bit longer. If you're just looking to maintain speed, such as on a highway that climbs a slight grade, it becomes very tiring to be unlocking TCC, accelerating above target speed, then having TCC lock again when you release throttle. The trick seems to be to balance the engine's torque output with driver preference.
    I balance it with MAP. I let the converter unlock at 75-80+ KPA.

    Anything would be better than the 2.8 TCC settings. The converter only unlocks below MPH threshold or WOT. I had an 87 and the settings were horrible. I ended up using Astro van settings and it drove alot better.
    Last edited by Fast355; 01-10-2016 at 08:22 PM.

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    I knew you were not using $42. I was just commenting that it was wrong ~everywhere~ for $42 so your definition file could have the descriptions wrong too. Historically, lots of stuff got copied from $42 since it was one of the first systems widely hacked.

    I'm sure you have figured it out by now, but the speed scalars work the same way as the %TPS tables. The TCC can lock above the upper speed (if %TPS allows) and the lower limit forces unlock once below that speed. The area between can be either locked or unlocked depending on if you are accelerating or decelerating. If you are in the middle and unlock via %TPS then it won't lock again until you go above the upper speed.

    Quote Originally Posted by 1project2many View Post
    In many cases it's OK to leave TCC locked a bit longer. If you're just looking to maintain speed, such as on a highway that climbs a slight grade, it becomes very tiring to be unlocking TCC, accelerating above target speed, then having TCC lock again when you release throttle. The trick seems to be to balance the engine's torque output with driver preference.
    Yes, this is why I commented to tweak as necessary. For my area, 10% above cruising throttle mostly covers grade cases. You may need to set the TCC unlock higher to suit your driving style and terrain.

    I just find that many factory calibrations have a large spread and require so much throttle for TCC unlock that you've reached the throttle level where downshifts occur by the time the TCC unlocks, and that is just plain annoying. In an application geared towards performance use, I want to the TCC to unlock fast as the throttle is pressed and then the downshifts to follow as even more throttle is added. Basically, a nice progressive reaction to throttle from the transmission.

    On the other hand, it may be desirable to keep the TCC locked in a truck while towing a load to avoid creating more heat in the transmission.
    Last edited by lionelhutz; 01-10-2016 at 08:31 PM.

  7. #7
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    Quote Originally Posted by lionelhutz View Post
    I just find that many factory calibrations have a large spread and require so much throttle for TCC unlock that you've reached the throttle level where downshifts occur by the time the TCC unlocks, and that is just plain annoying.
    That is exactly what I am trying to avoid.

    Again, THANK YOU for explaining this better as it should also help others in the regard of a new transmission, or, a new TBI conversion.

    If I recall correctly, the tables in the $42, the TPS percentage table is labeled as %TPS where as in the $4E, they are labeled TPS.

    Values look somewhat close.

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    So I tried 3rd and 4th gear lower/upper % values from a different BIN.

    When I initially started out, I was using a BIN that had these values set to 100% and this I believe is do to those engines using vacuum to control the TCC.

    So the alternative to manipulating numbers in the BIN is reconnect the vacuum switch and try to make a note of every time the TCC locks and unlocks, unless there is a way to flag time points while recording a datalog in TunerProRT that I don't know about.

    In any case, one BIN is for a Brevada with the 4.3 and the other is a BIN from a 2.8 with 3.73.

    While looking at the values, the 3rd gear upper/lower % values are the same. The 4th upper/lower % values are different.

    So the differences are not because of the differences in the throttle body levers as they are of different styling, so it has to be something else, and I suspect that to be the rear gear ratio.

    (Note to self when I look at this thread later today: look at map value and TCC state in last two logs. Note TPS value and TCC state at map values below 8")
    Last edited by damanx; 01-25-2016 at 03:05 PM.

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