super delayed 1-2 shift (soft not hard) still throwing code for shift solenoid after change

p8ntballa9362 · October 13, 2018

alright fellas ive come to the end of my friggin rope. got a '00 silverado 1500 z71 w/ ~300k miles. until lately shes been running like a top.

my problem started out of the blue really, it shifts really late into 2nd. if im giving it some good gas it might not shift into 2nd until 3500/4000. only thing is, it doesnt jam into 2nd. its not slipping, its just shifting really late. if i let off the gas for a whole second it will shift fine. the other thing is if im driving fairly slow, 30-40-50 and punch it, it will kind of wound out the trans and shoot up real fast. it started doing all this, and i decided to change the trans fluid/filter. im almost positive it didnt throw a code before i changed it. at first i think it mightve gave me the "trans component slippage" deal, but now its giving me a p0756(i think) shift solenoid A code. i drained the bastard again and replaced both of those solenoids. nothing.... same old shit.

ive seen some stuff about TPS sensors and accumulators. i tend to think its an electrical or pressure issue. i say that because it stands to reason that if it were a clutch/mech issue it would either be slipping or jumping into gear...or not shifting at all. so im at a loss right now.
PS- come to think of it, years ago when i would take REALLY long trips or get the trans going hard (mountains,etc...) it would jump real hard after id come to a dead stop, but i heard that was a common prob with the 4l60e's just boosting the line pressure too high incorrectly.

KARNUT · October 13, 2018

At 300K miles a good educated guess would be a rebuild is in order.

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carkhz316 · October 13, 2018

Well, during the 1-2 shift, solenoid A is commanded off, so unless you have a shorted solenoid or harness (not unrealistic for a wire in the internal harness to be bad), I'd look into other areas, namely MAF sensor and TPS issues as they can throw off shift timing as well.

p8ntballa9362 · October 14, 2018

13 hours ago, carkhz316 said:

Well, during the 1-2 shift, solenoid A is commanded off, so unless you have a shorted solenoid or harness (not unrealistic for a wire in the internal harness to be bad), I'd look into other areas, namely MAF sensor and TPS issues as they can throw off shift timing as well.

thank you, this is what i was thinking. come to think of it if im idling or barely applying throttle and getting up to speed, it shifts right on time like nothing is wrong. so much so that i wonder if its in first or second. say its a bad tps or maf sensor, why would it still throw a shift solenoid code?