It's a 1990 GMC, 350, 2 wd. When I accelerate from a dead stop it slips for a split second then works fine from there. If I slowly ease on the gas & the truck has started to roll it doesn't do it, and from there it doesn't slip at all. When I come to a stop I can feel it "disengage" for lack of a better term, but I can tell it's the same thing. It does not slip in reverse gear, and it doesn't seem to do it on initial startup after the truck has sat long enough to cool down. I had the fluid changed at Valvoline and that seemed to improve it slightly. The fluid that came out was dirty but it didn't smell burnt. I could tell it hadn't been changed in a while. I set the TV cable, which had stretched some and that seemed to make it less prone to slip but it still happened. I'm curious if this is a symptom of something fairly common, and if I'm lucky maybe something I can fix myself - or at least go to a tranny shop armed with a little knowledge. Thanks in advance for any help.

 

For a quick fix you could install the .500 main boost valve, this can be done when the pan is off. When you adjusted the TV cable did you have it set so that the TV cable is tight at WOT?

 

I used the self-adjust method as I didn't have anyone to help me with it. After driving, based on the shift points & how it shifts I think it's very close to being adjusted correctly. When I get a friend over to help for a few minutes I'll use Transfixleo's method & ensure the cable it tight at WOT, but it's very close now. If it persists I'll replace the main boost valve as you suggested - where can I get one of those? Do tranny shops or speed shops typically sell them? Thanks for your help.

 

If you need this valve, it sells for about $10.00. Let me know?