I have a 2 spd powerglide in my 68, it is not down shifting into 2nd. Even when you start it in first and let the rpm get high and shift to drive. What is going on here?

Jim, you do mean up shifting to 2nd. Right? Low (1) and Drive(2) is all you have. It stays in first the whole time? Linkage may need some adjusting. Trans was working at some time? Kevin

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69' SS-350 ragtop, M20, 3.55 posi. Totally Disassembled & in boxes (I'm working on it!)
69'(Hugger Orange -originally, Burgundy now) Z-21 ragtop 327/PG, Driver

If it's not shifting into drive the first thing to check would be the vacuum modulator and or the vacuum line to it.

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Robert

'69 getting better every day... (every pay day)

It was working fine, will check the linkage and vaccum line. Would the throttle linkage do this?

Throttle linkage determine upshift point for WOT.

Vacuum modulator does for the rest of the throttle positions.

If you find both in good shape and adjusted correctly, you may have to remove valve body and give it a good cleaning and emery cloth the valves. Clean with Brakleen and assemble with ATF. Make sure weights in governor are intact , these are located on the output shaft, jack car up in the rear, use stands, rotate driveshaft slowly, you can hear the weights move on their axis inside.

Do a line pressure check at your local trans shop, to make sure oil pump is up to snuff. Second gear is a locked up planetary gearset via a piston driven by oil presssure from the oil pump. If not enough oil pressure, no 2nd gear.

Food for thought

Everett 68/350/PG/11.90/115mph