Chevy Express Van Transmission Recall

:S Doh! You are correct, forgot they are 6 speed now!

BurbMan wrote:
Guessing this is the 4L85E transmission.

6L80E, or 6L90 for the DuraVans

Guessing this is the 4L85E transmission.

Can I start the GM bashing?

Figures, leave it too GM to make a fix like this!

Just kidding. It doesn't say anywhere what the exact fix is, it may reduce power, change the TCC lockup schedule maybe even increase line pressure. Maybe just as simple as turning on the trans temp light sooner. It's hard to say unless we know the exact programming changes. At least they are doing something about it. Instead of just letting the consumer or GM eat a tranny!

I had the reprogramming done yesterday. Any difference in performance or drivability was not noticeable during the casual driving back from the Chevy dealer. I did notice that it still runs 2000 RPM at 62 MPH, just like before. It should not affect highway mileage. So I've got that going for me, which is nice. :) It might be keeping the TC unlocked more often in lower speed ranges.

Yes it will. The choices are pay more in gas, or replace the torque converter. Even with high gas prices, gas is cheaper than a torque converter.

I am shooting from the hip on this, but my guess is they are all 6.0L V8's.

So keeping the TC unlocked more often is gonna hurt gas mileage, right?

Thanks for info

Missed that and am guilty of speed reading with a jump to the clutches inside
the tranny

But by unlocking the TC clutch under those kinds of conditions...will have the
fluid heat up faster/more while towing. That would only move the problem to
the ATF and it's heat management system

Sounds like GM undersized the TC clutch for this vehicle. Doesn't say what
engine is involved.

BenK wrote:

With the natural 15% or higher slippage of an TC and that subsequent
torque multiplication...this is all funneled through the food chain
down to the tires

Yes and no. There is 10%-15% slippage in the converter when it is unlocked. This bulletin refers to the torque converter clutch. When the clutch is applied there should be ZERO slippage. Apparently there is more than zero slippage, and that is causing excessive wear. An unlocked converter causes exactly zero wear to the torque converter clutch.

BenK wrote:
The re-program will reduce the amount of power allowed. So performance
will be degraded

Why would you make this assumption? Maybe they are reducing power, but it makes more sense to me that they are reprogramming it to unlock the converter where the converter clutch would be overloaded. That would solve the problem with much less customer dissatisfaction than by reducing power.

Also, if the problem exists at part throttle, then reducing power does almost nothing to solve the problem. People drive by speed, not by power output. If they want to maintain a given speed they press the go pedal far enough to maintain that speed. If part throttle power is reduced they just push the pedal a bit further to maintain that speed. Then the load on the converter clutch is still too high and wear will be unacceptable. Unlocking the converter is the only solution that makes sense to fix this issue.

Thank you for taking the time to post this and taking a moment to
comment that this is the kind of potential component/system failure
from over loading

With the natural 15% or higher slippage of an TC and that subsequent
torque multiplication...this is all funneled through the food chain
down to the tires

The re-program will reduce the amount of power allowed. So performance
will be degraded

Again, thank you for posting this