1990 GMC Sierra Transmission Problem

JUSTLANG12

MEMBER
1990 GMC C1500

Just a quick question here. My brother has a 1990 GMC Sierra 1500 4-wheel drive, automatic. He put a new engine in it (5.7 TBI) and he said his tranny worked fine for about a month. Now he says its stuck in first gear. He can get it to shift to second if he does it manually but cant get third or fourth. Is there a vacuum module or something that he may have forgot to hook up or does he need to hook a computer up to it and reset the transmission? Maybe its just shot too. I plan on fixing it for him so alittle input would help out. Thank you for your time.

Sunday, June 3rd, 2007 AT 6:50 PM

1 Reply

MDASEY

MEMBER
1 POST

Check out the following web site: www.700r4. Com

This is an excellent site for the transmission used in this vehicle. I suspect that the problem is with the adjustment of the TV cable. I too have a 1990 GMC Sierra. It was not shifting properly either. I followed the procedure for making the adjustment and it now works better that it ever has. You said that the engine had recently been changed. I assume that you used the original transmission on the "new" engine. This is probably where the adjustment got out of whack. Check it out. Good Luck.

Was this

answer

helpful?

Yes

No

-1

Monday, June 11th, 2007 AT 8:09 PM