4L60E shifting problems...fighting with trans shop and no leg to stand on

[hrspwrfreak]

Hi, I have a 96 4x4 chevy truck with the 4L60E trans...it was rebuilt about 10k ago and i am not very happy with shift quality. unfortunatly i never got to drive the truck with a good trans to compare shifts because when i bought the truck, the trans went the next day. Here is what it does...1-2 shift is "overlaping" (so they call it) and it seems like way too much.... What can be done about this?? On the 2-3 shift especialy under any load the rpm will flare 200-300rpm...it has done this since day one and the trans shop says this is normal....WHAT?? I installed the b&m electronic shift improver but that does not help much although i can tell it does shift a little firmer but i want this trans to shift good before i put aftermarket add ons to it. What can i do? I see different servo's etc, etc. Is that anything to consider?? The gm recall has been done to jump the computer wires, I think this was for a faulty ground? Thanks for the help

 

[bruce]

OBD II.
No hacs or practical way to reprogram it.
Your at everyones mercy on that deal.

 

[hrspwrfreak]

So what your saying is...Im sheet out of luck??...LOL

 

[bruce]

Originally posted by hrspwrfreak
So what your saying is...Im sheet out of luck??...LOL

Yep.
I've done some work reprogramming 95 LT1 Caprices, and you can get that tranny to be really sweet, IF you can reedit the programming.

 

[quickt]

A flair is a shift timing issue. The PCM does not effect the timing of the shifts. Solenoids are on or off. A flair is not normal for a 4L60E.

 

[bruce]

Originally posted by quickt
Solenoids are on or off.

Yes, but using Pulse width modulation, the can modulate the flow past them, and in essence have them slowly turn on and off.

 

[quickt]

Originally posted by bruce
Yes, but using Pulse width modulation, the can modulate the flow past them, and in essence have them slowly turn on and off.

Pulse Width Modulation (PWM) is simply for the torque converter lock-up. PWM has nothing to do with the shift solenoids. Shift solenoids are on or off. You turn one on or off boom shift happens. The shift soleniod feeds are from .025-.031. You could slow a solenoid down as slow as you can it will not affect the shift timing to cause a flair. You can remove the PWM solenoid and the trans will still shift. You will set a code and trans will not lock up but it will shift.

 

[MeanBuicks]

Lonnie's correct.

The flair is most likely caused by excess band clearance and/or a loose 3-4 clutch pack set up. Have the tranny shop (or another one since they think a flair is normal ) check the band clearance and adjust it down to 0.060"-0.80". This is done with selective length apply pins.

The 1-2 shift may clean up a bit by installing a stiffer 1-2 accumulator spring assuming that the band isn't glazed at this point.