TCC Lockup Issue

[joecar]

I'm still scratching my head , I'll have to think about this...

[SSpdDmon]

Can you post up the TCC apply tables too?? (Thinking apply tables need to be greater than the release tables for a given TP%.)


**EDIT** Looking over the logs, my first impression is that the PCM is trying to tell the TCC to lock, but it's slipping (not unlocking). What does your {D2905} TCC Pressure Apply Rate look like? If you're running a smaller, aftermarket converter...you may need to increase {D2905} and possibly {D2902}. The reason being...smaller converters have smaller TCC's. Therefore, there's less friction surface area for the clutch to grab, which may require more aggressive settings in the PCM.

[DrX]

Can you post up the TCC apply tables too?? (Thinking apply tables need to be greater than the release tables for a given TP%.)


**EDIT** Looking over the logs, my first impression is that the PCM is trying to tell the TCC to lock, but it's slipping (not unlocking). What does your {D2905} TCC Pressure Apply Rate look like? If you're running a smaller, aftermarket converter...you may need to increase {D2905} and possibly {D2902}. The reason being...smaller converters have smaller TCC's. Therefore, there's less friction surface area for the clutch to grab, which may require more aggressive settings in the PCM.

I was running all the stock TCC Apply/Release tables during that last log. Still had the release in 3rd issue whenever the throttle was released. The tables shown above are bumped up from stock and so were the corresponding release tables. I couldn't see any conflicts between those Apply and Release tables or the factory tables.

I have always left the pressure tables stock as I wasn't sure whether an increase was needed with the triple disc converter. D2902 is 827.

D2905:


In the log it looks like the TCC is slipping at lockup in 4th only and TCC DC % increases until lockup is accomplished then drops off. The converter fully locks in 3rd but releases immediately when the throttle is released.

[DrX]

Just took a closer look at the stock tune and it looks like it was never intended for the TCC to apply in 3rd. The TCC apply speeds for 3rd are all higher than the 3-4 shift speeds.

So I was thinking that perhaps there is no "Coast" mode for 3rd written into the tune. But I was playng with the Throttle Cracker table trying to get TP as low as possible when coasting and I did log a couple of short "Coasts" in 3rd before the TCC released. Could be some unseen tables??

Also noticed that on a stock vehicle the TCC never completely locks. There is always a little slip, say 40-50 RPM whereas mine goes to 0 which might explain the harshness. Seems that I read something about this before. I'll have to re-read the TCC "Description and Operation" in the service manual.

[DrX]

In the stock tune, the TCC release in 3rd is also at or above the 4-3 downshift speed. So the TCC is never locked in 3rd. The tables are setup so that the 3-4 upshift initiates lockup and the 4-3 downshift initiates release.

[ScarabEpic22]

Keep us updated, I have a similar issue with my 4L60E trans being fine until 4th TCC lockup when it is weird and I cant figure it out.

[driver456]

When I had a problem with TC locking & unlocking some one on the forum told me to set {C5601} MISFIRE DETECTION MAX TEMP to 1 degree and the problem is gone.Normal was 266*....................Paul

[DrX]

When I had a problem with TC locking & unlocking some one on the forum told me to set {C5601} MISFIRE DETECTION MAX TEMP to 1 degree and the problem is gone.Normal was 266*....................Paul

Haven't tried disabling it that way. No misfires logged with it active though. Unlock only occurs when the TP falls below 10% under coast conditions. Doesn't matter what speed I'm at

[DrX]

This is the description and operation of the stock TC from the service manual:

"A torque converter with an electronically controlled capacity clutch (ECCC) This transmission is equipped with an ECCC. The pressure plate does not fully lock to the torque converter cover. Instead, the pressure plate maintains a small amount of slippage, about 20 RPM, in SECOND, THIRD, and FOURTH gears, depending on the vehicle application. ECCC was developed to reduce the possibility of noise, vibration, or chuggle caused by TCC apply. Typical apply speeds are 49-52 km/h (30-32 mph) in THIRD gear and 65-73 km/h (40-45 mph) in FOURTH gear. Full lockup is available at highway speeds on some applications."

My PI Vigilante TC completely locks and at a higher speed as per the tune. Could explain why it is so noticeable.

[ScarabEpic22]

Interesting, well I cant try playing with that parameter as the LL8 doesnt have it...