Hi my 97 express 3/4 ton cargo van with a 305ci has been shifting hard for some time, years in fact. When it started this, I changed the fluid and filter. Say you go more than 5 miles on the interstate then get off and stop at the bottom of a ramp. After you start out again it would bang gears. In town, it generally wouldn't. THEN, I had a spark plug wire (#1) fall off and the truck ran very unsmoothly although it shifted fine even after several high speed miles. When I discovered the loose plug wire at the distributor and re-attached it, the tranny started is crap again and shifts hard now. If I throw the tranny in neutral and kill the engine for a few seconds, then restart, the tranny will shift fine again. Any suggestions? Someone suggested I may have a stall converter issue but I think it's a vacuum problem.

 

I have '99 Express Conversion with 5.0. I had about 40,000 miles when it was still under warranty and the trans had to be rebuilt...something inside caused metal shavings to get in fluid causing some block or somesuch thing...so dDealer swapped out a rebuilt one...I was on on edge, becuase it was $2250 to do the work and I expected the extended warranty to cover it. They had to call the extended warranty "detective" in. It was covered, since it was not "normal wear-and-tear".

So I think you should have the trans inspected by a shop or by you if you know what you are doing. You did not say how many miles are on it, or if you have checked he trans fluid level, color -or- repacing the trans filter etc. I am not an expert, but I know what is beyond my knowledge to repair, hence I seek advice from the pros.
--SteveMc