1985 Chevrolet Silverado drives but won’t shift

Will drive but will not shift auto tran 1985 chevy Silverado. C 10

When was the last time the transmission fluid was serviced?



Reverse works? It goes into gear and moves forward but only has 1 gear, as in no shifting?

Can I assume this old automatic transmission has a governor?

If the fluid level is OK pour a bottle of trans-medic in the transmission and let the engine warm up and then try a few force shifts, i.e., with the shift lever in 1 drive the car up to a speed well beyond the normal shift point and then move the lever to 2. After a few stops and restarts doing that often the stuck component will break loose.

But as a rule proper maintenance will prevent that problem. And it’s possible that there is already damage that prevents the shifting. If so the cure will be costly.

It does, in the tailshaft housing iirc.