Transmission will only work in reverse will not go forwards

TIMOTHY MILLER

MEMBER
1996 GMC SIERRA
5.7L
V8
4WD
AUTOMATIC
220,000 MILES

I had a mechanic put in a salvaged transmission that he rebuilt. It will go in reverse and runs fine but will not go forward at all. Is there something it could be or I can check that would cause this without taking out the transmission and what should I check and possible replace if I have the transmission taken out? My mechanic not sure what it could possible be. Please help with ideas or if you know exactly what problem is and what to do to do to fix it? Please and thank you.

1 Reply

PATENTED_REPAIR_PRO

MECHANIC
1,853 POSTS

Sounds like the forward clutch is not working.
Did he replace the forward clutch piston seal?
These are all of the possible causes inoperative In "drive":

1. Low fluid level. Low fluid pressure. Manual linkage mis-adjusted or disconnected. Damaged torque converter. Leaking or damaged transmission case seals or gaskets. Damaged oil pump drive shaft or pump assembly. Broken bearing, pinion or carrier. Roller clutch damaged or locked.
2. Piston or seal damaged in forward clutch assembly. Forward clutch assembly clutch plates burned or missing, or check ball capsule leaking or missing. Burned reaction plate (due to lack of lubrication), broken snap ring or worn gear teeth.
3. Rear gear set assembly pinions, internal ring gear or sun gear damaged. Main shaft damaged. Parking pawl spring broken. Turbine shaft ball not seating.