1999 chevy silverado hard shifting

I have a 1999 chevy silverado 5.3 4wd w/ tow package. I bough it with 30,000 mi. It has always had a hard shifting/clunk after long drives or sometimes short ones that involve a lot of elevation. Oddly, if I stop and shut the car off for a minute or two the hard shifting stops, but eventually starts again. The truck now has 160,000…still with the shifting issue. What is this and with this many miles is it serious?

Has the fluid and filter been changed recently. If not have it drained and refilled. Do not have it flushed. With high mileage vehicles the flush can push contaminates into the small passages of the valve body and really screw up the tranny.

Should I use a synthetic fluid?

@joyr…no need for a synthetic in this transmission.


Just use Dexron 3.