Transmission problem, 98 gmc sonoma, cant figure out what is wrong?

[David]

i have a 4.3l gmc sonoma with an automatic transmission, and i was driving it around, everything was fine, wasent in 4x4 or anything, and i got it to 5000 rpm and it will usually shift and not go any higher, but it dident shift and the rpms almost got to 6000, parked it later at a buddys house and later found out i dont have reverse anymore, and when im driving it wont shift, i have to let off the gas when im at about 20 mph and it will shift, same when i get to about 40, etc, and i cant hit the gas very hard or the rpms jump to about 4000-5000, i checked my fluid and it seemed to be dry, i added fluid, and problem still persists, im guessing i grinded the shit out of my gears or something, im hoping thats not what it is though, any ideas on what i need to replace, thanks

 

[Molson02536]

i have a 4.3l gmc sonoma with an automatic transmission, and i was driving it around, everything was fine, wasent in 4x4 or anything, and i got it to 5000 rpm and it will usually shift and not go any higher, but it dident shift and the rpms almost got to 6000, parked it later at a buddys house and later found out i dont have reverse anymore, and when im driving it wont shift, i have to let off the gas when im at about 20 mph and it will shift, same when i get to about 40, etc, and i cant hit the gas very hard or the rpms jump to about 4000-5000, i checked my fluid and it seemed to be dry, i added fluid, and problem still persists, im guessing i grinded the shit out of my gears or something, im hoping thats not what it is though, any ideas on what i need to replace, thanks

Slow, slipping or no reverse: “lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or broken sunshell. It is possible to remedy a fluid problem by removing the checkball from its cage in the case in the rear of the trans may help (must remove valvebody), or adding a high-viscosity additive such as Lucas Transmission additive or other seal restorer product. May also have worn boost valve (can replace in the pan).

Put a transmission line pressure gauge (or visit a local trans shop) on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.490" boost valve (easy fix in pan)

1-2 shift does not happen at WOT until you let off the gas: Best case: try replacing the TPS. Middle case: leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator). Doublecheck by using the pressure gauge and watch for a big drop when the PCM commands 2nd gear. Worst case: poor line pressure rise.

Good luck and hope this helps, keep me posted, be glad to help.