Alright, so i went to my dads shop, had a transmission tech ride with me using his diagnostic computer.

he was noticing a lot of slippage in my transmission when the rpms were fluctuating, and even some when it wasnt fluctuating but i was accelerating. my most recent check engine light was a transmission slip code. and its back on again after clearing it. he also noticed hard shifting from 1st to 2nd gear.

he matched the problem to a technical service bulletin relating this problem to the valve body. I dont really know much about transmissions but supposedly you can keep your valve body if it is in good shape, and just replace the valve? assuming you know who can do that etc, theres a guy here that would do them for $150, but i can get the whole valve body through my dad for $206, plus a filter kit for another 35 bucks or so.

im gonna get the labor for only $100 through a tech that my dad has helped before so thats cool. roughly $350 to have a valve body replaced and hopefully resolves my transmission slippage, check engine light, and hard shifts from 1-2.

i really appreciate all of your thoughts and help trying to diagnose this, seems a transmission is pretty hard to diagnose without a computer...

ill post back here if it fixes it so anyone with similar issues may know where to look for solutions

thanks again for the help, you are a wealth of knowledge!

justin

 

I have had the SAME problem with my 1998 4.3 for the last year or so. But there are a couple of differences. Like I havent had one code come up, other then one having to do with an O2 Senser. Which was resolved, and I have replaced and upgraded my reverse booster, Shift servos,and torque converter. With ABSOLUTLY no luck. Along with that the transmission was rebuilt just 6 months before the problem showed up!! I am at a complete loss...

I did Find a Valve Body Kit that is sold by this company called Whatever It Takes, that supposedly Improves shift firmness Includes a high quality bypass booster valve & sleeve to restore correct torque converter clutch function. Restores main TV booster pressure function with the Patent Pending "Booster Recovery System™".

From what I have read, from 1998 and up GM changed the way lock up with the TC applies," before then was either off or on". Now lock up applies gradually which works this valve very hard. The kit blocks the valve open so apply is basically on or off again.

I could really use your guys knowledge on this one

 

I had this problem for quite awhile on my '96 Sonoma, pretty much identical symptoms. I changed the transmission fluid and filter; no improvement. If I got up to a certain highway speed, the RPM flutter would go away, but over time it didn't matter how fast or what RPM's, always fluttered. So I rigged a switch that fooled the tranny into thinking the brake was always on, so the TCC wouldn't go in (check it out here...scroll down about halfway). No RPM flutter, but lost an MPG or two due to higher RPMs on the highway.

Eventually the SES light came on, but at the time I didn't have a code reader; I assume it was the same codes as mentioned here. Then my reverse gear became sketchy when the tranny was cold; didn't want to engage very well. Finally the whole tranny got to the point where it would slip and barely run. I was ready to junk the truck...was not my daily driver anymore and had about 180k miles.

So as a last-ditch effort, I changed the tranny fluid and filter one last time. By some miracle, the transmission cured itself and has been perfect ever since with no codes (this was 3 yrs ago). Apparently it was the 2nd tranny fluid/filter change that did something...no idea what (there was about 30-40k miles between fluid changes).

But if you're like I was and had no intention of spending any more money on a high mileage truck, rig up that switch and say goodbye to RPM flutter.