1997 chey pu auto trans 1st and 2nd shift good drive doesn't shift until rpm's are 3500-4000 rpm

then the problem will be in the wiring harness and connections

1st Suggeston mke sure youare pressing brake pedal while trying to shift gears.
2nd Suggestion if this doesn't work check your neutral safety switch on transmision .
Good Luck!!!

I had a friend that had this problem.I work at a G.M.dealership and I ask a friend that does trans work there.He said this is normal in cold weather.This is done in order for the trans to reach operating temperature sooner.This could be why you are unable to fix this problem because it is normal.I looked in service info to see if I could find a bulletin or something to back this up but I did not find anything.I know this guy very well and I know he knows his work and is good at it.Hope this helps.Good luck.

Check your tranny fluid I had a similer issue with a different truck and it was a clogged trans filter which caused it to pump the fluid up the dip stick I changed the fluid and didn't have an issue again until I blew the engine. So I would change that first regardless.

if it has a kick down cable that could be the problem look for a cable running from throttle to trans that can be adjusted in length

check vacuum and electrical connections

It has nothing to do with the transmission, it's your engine mount thats bad.

Had the transmission serviced in a while? would be a good idea to have someone look at it for you. I wouldn't continue to drive it until you do a diagnostic and have it properly serviced. Transmissions on that truck could cost you upwards of $7,500. and I think you would prefer spending the $ 350. it would cost for a servicing.

check the ground on the ecu and the ground off the alternator and the fuse block. most times it could be bad or innsufficient voltage going to controls. if the blower works intermittently it could a wicked ground somewhere. did you have anyone install a radio or sound system in the truck by any chance?

you need to replace clutch pack for that gear can be ordered seperately from parts store or dealer if you want to save money call peach street auto recycling at 1800-365-2341 for a warrantied used one! also might be time for change trans filter and fluid filter could be slightly clogged but I lean towards clutch pack I replace these alot on Hondas