1990 GMC Sierra transmission

NICKAN

MEMBER
1990 GMC SIERRA
5.0L
V8
4WD
AUTOMATIC
300,000 MILES

Hi guys I have a 1990 gmc sierra k2500 700r4 trans 5.0 v8, old tranny slipped real bad, put in a new rebuilt 700r4 yesterday, now today I noticed I don't shift out of my 2nd gear till my engine temp gauge is reading around 180-190ish, if it matters, old tranny did similar things, it wouldn't LOCK into 3rd until 160-170 and would have no OD till 180-, any advice on where I messed up an how to fix it would really help, thanks

3 Replies

HMAC300

MECHANIC
48,601 POSTS

Scan for codes first see if anything comes up and make sure throttle pressure is adjusted correctly. It may be that the trans seals are bad when cold then work when heated up a tad. But a trans guy can give a better opinion as the do these things all the time where as most mechanics don't.

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Monday, October 5th, 2015 AT 7:57 AM

NICKAN

MEMBER
2 POSTS

Are u talking like takin it to autozone an there scan tool? Or a real shop? And im not even to sure that my 1990 gmc on its 4th motor 4th trans can run error codes any more. As to the tv cable, How would I go about tuning this? Iv talked to tranny guys, a few, cant get one straight answer. Do you think driving my tranny at this pouint is going to cause damage?

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Monday, October 5th, 2015 AT 8:08 AM

HMAC300

MECHANIC
48,601 POSTS

To get codes check under OBD1 on how to repair you cross a&b on aldl at bottom of dash watch check engine light count flashes. You can't hurt trans anymore than it already is. If it works ok warm andnot cold its' not throttle cable.

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Monday, October 5th, 2015 AT 9:31 AM