1988 GMC C1500

Tiny
TIMAGATES
  • MEMBER
  • 1988 GMC C1500
Transmission problem
1988 GMC C1500 V8 Two Wheel Drive Automatic

I just replaced the throttle valve cable or also called detent cable in my truck now I'm having problems with it shifting from 1st to 2nd and to 3rd it wants to ride each gear way longer than it should and then it slams in to the next higher gear, I've adjusted the cable all different ways and it still shifts hard what am I doing wrong or is there a another problem I'm not seeing
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Tuesday, October 19th, 2010 AT 10:17 AM

5 Replies

Tiny
HMAC300
  • EXPERT
To adjust it properly, first disocnnect the cable from the throttle, then push the blakc button on the cable by the throttle. Reconnect the cable and open the throttle all the way with the engine not running. That is all there is to adjusting the cable. Road test it and see if it stil does what you are talking about. If it is a 350 thencheck to see if your vacuum line has a hole in it or is soft at the modulator. If it is reapir that. Then road test if it still does it then take it to a trans guy and have him take a look at it.
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Tuesday, October 19th, 2010 AT 2:13 PM
Tiny
TIMAGATES
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OK it shifts now, but it whines through 1st and sec for a real long time then it slams into gear. Sounds like my tranny is going to blow up, what am I doing wrong
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Wednesday, October 20th, 2010 AT 11:58 AM
Tiny
HMAC300
  • EXPERT
Follow the seps that I gave you to adjust the throttle pressure. If it continues to do the same thing, then you may have a valve hanging up or a govenor sticking. Take it to a trans pro and let him diagnose it.
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Wednesday, October 20th, 2010 AT 7:01 PM
Tiny
TIMAGATES
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Found out last night that the engine is not the original and the guy I bought it from passed away and his family doesnt know
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Thursday, October 21st, 2010 AT 11:23 AM
Tiny
HMAC300
  • EXPERT
Not having an original engine is son big deal as long as it was the correct one to replace it and the regular stuff was used to hook it back up. I really think you ought to have a trans guy look at this as you not being a professional and may be missing something you know nothing about, meaning the way a trans works.
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Thursday, October 21st, 2010 AT 12:34 PM

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