Help! 94 Transmission Issues PLEASE HELP!

[Towu4free]

hey guys, im hoping you can help me, my 94 vette has the 4L60E Auto trans in it, the car has 130k on it, i changed the fluid when i first got it a few months ago... heres what it does, in normal driving and acceleration it does just fine but if i launch from a dead stop at WOT it goes all the way up to the peak of the tachometer and sounds like to me its a " double shift" its hard to explain almost as if for a split second it hits Neutral then goes into gear...this may sound dumb but try to picture this as the engine..... baaaaaaaaaaaa-ba-ba-baaaaaaaaaaa any suggeestions?
(first) (The shift) (second)

 

[badglas]

Bad shift

Have you tried adjusting the detent cable? This is the main adjustment for shift points based on throttle opening.

Ron Kane
Benchmark Corvette Service

 

[Towu4free]

Have you tried adjusting the detent cable? This is the main adjustment for shift points based on throttle opening.

Ron Kane
Benchmark Corvette Service

I havent tried that, i didnt think the 4l60E had one...where would i find it? i thought it was all electronically shifted...there isnt any cables coming from the throttlebody to the trans..

 

[badglas]

shift

My mistake, no detent cable. PCM does retard the timing on this model before each shift, could be what your feeling. I would think a valve in the valve body or its respective control servo would show problems elsewhere. One other thought; check TPS voltage at WOT and make sure it is less than 5 volts. Also watch for dead spots in the voltage while doing a full throttle sweep. May sound silly; do not try these tests on a running engine. I have found stating the obvious is safer than not.

Ron

 

[Towu4free]

well badglas, i really do appreciate your help, i will check that first thing tomorrow!, also i failed to mention that when i do launch it if i let off just a hair befor it gets to the top of the tach and does its "thing" is shifts ok, its almost as if its at 100% throttle it does it but if i feather it for a split second between 95-99% it shifts ok and i can mash it down to the floor and go on down the road... thank you again, and let me know what you think and ill will post my finding tomorrow

 

[Towu4free]

UPDATE

I put the vette on our snap-on modis scanner today and at full throttle it only measured 85%. So I adjusted the cable, now it reads 99%. Do you think this could have anything to do with the transmission shifting? I haven't driven it yet and the TPS censor reads .6 at idle and 4.12 at WOT. Thanks guys, and let me know.

 

[Hib Halverson]

Don't let off the gas just before the shift.

Now that you've got 99% TPS at WOT. Road test the car by putting it in drive and accelerating with your foot on the floor. Do not lift. In first gear, the engine should go to just short of the rev limiter then upshift.

 

[black_771]

hey guys, im hoping you can help me, my 94 vette has the 4L60E Auto trans in it, the car has 130k on it, i changed the fluid when i first got it a few months ago... heres what it does, in normal driving and acceleration it does just fine but if i launch from a dead stop at WOT it goes all the way up to the peak of the tachometer and sounds like to me its a " double shift" its hard to explain almost as if for a split second it hits Neutral then goes into gear...this may sound dumb but try to picture this as the engine..... baaaaaaaaaaaa-ba-ba-baaaaaaaaaaa any suggeestions?
(first) (The shift) (second)

Mine does/did the exact same thing! Kept messing with it and nothing helped. I ended up changing the trans fluid and then it would slip so bad it was undrivable. Not sure if the two are related, but maybe the trans has seen better days. I ended up rebuilding it in the end.