I have a 350 hydra-matic. Just recently, it won't shift out of first. It will go in reverse. I replaced the vacuum modulater and the hose going to the modulator. I even put a larger diameter hose on. Still wont shift out of first. What can I check next?

 

Your local transmission shop, for a price!!
Could be a broken sprag, stuck piston in the valve body, even a stuck check-valve, but if you're unfamiliar with automatics, you're at their mercy!
Sure, you coud order one from B+M, or another big-name trans builder, and pay to install it, but ask your local guy for a shift kit, and a one-step-up converter, and you should be around a grand with a year warranty.
Don't 'downshift' and it'll last longer!

 

Will it shift if you manually go through the gears? It may also be dirt in the trans. Buy have it checked out first before you go and buy a new one. It may be cheaper to have it fixed.

 

Verify that you have manifold vacuum at the modulator before you spend any money on parts or repairs. Also, will the trans upshift if you keep accelerating? If the modulator (or vacuum source) is bad, the trans should upshift from first to second at around 45-55 MPH.

 

Yep thats why I was asking if it would shift manually. When I got mine it would not shift to second gear til you hit about 45mph. I replaced the modulator, and still the same thing. The problem was the vacuum line was torn behind the intake, and there was no vacuum.

 

Its the upshift governor. The springs in there are so loose that i hard time getting the round cover separated from the governor shaft.