Help with Transmission Diagnosis

1999 CHEVROLET TAHOE

DKTHOM7

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Transmission problem V8 Two Wheel Drive Automatic 107000 miles

I have a 2 wheel drive 99 Chevy Tahoe with a strange problem. When I start the Tahoe in the morning it drives fine. After about 5 minutes of driving the transmission stops shifting. It appears that after the transmission warms up it loses pressure internally and just stops shifting, leaving the truck in neutral. Plus, all the time that this has been happening there are no trouble codes, nor does the check engine light come on.
Every transmission place and the local Chevy dealer all claim that they will do a diagnostic but the only response I get is that I need to have the transmission rebuilt. Is there any way to determine exactly what the problem is and have that fixed or do I truly need to have the transmission rebuilt?

Dec 16, 2008 at 8:31 AM

DOCFIXIT

CAR REPAIR CONTRIBUTOR
18,828 POSTS

A pressure test on trans will tell if it is internal. If pressures are good could be shift solenoid fault.

Dec 16, 2008 at 10:37 AM

KELLIE FEARN

MEMBER
4 POSTS

I had same prob and I had transmission rebuilt it cost me $1700 and it shifted fine for about a year and only 15000 miles and then it started acting up again. It only shifts into 1 2 but not into 3rd it just keeps reving. Now im stuck and After I paid a bunch to have it rebuilt.
Good luck

Nov 8, 2017 at 5:53 PM

STRAILER

CAR REPAIR CONTRIBUTOR
54,354 POSTS

This sounds more like you have a problem with a shift solenoid. Here is a guide that shows how to drop the pan and the wiring diagrams so you can see which solenoid to change out.

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

you will need to raise the car up safely.

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Here are the transmission wiring diagrams (below) It is the solenoid with the white wire.

Please let us know what happens.

Cheers, Ken

Images (Click to enlarge)

Nov 11, 2017 at 11:09 AM

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