Just got my '71 442 455 TH 400 back. Its been sitting for a couple of years. Now its not shifting correctly. 1-2 shift is at 5500-6000 rpm and it never goes into 3rd. Any suggestions?

 

Check the vacuum on the top of the intake manifold the hose maybe off or cracked.Or the hose by the transmission modulator or the modulator is bad or valve is sticking.

 

First ensure the fluid level is correct. Check to make sure you have manifold vacuum at your transmission modulator valve. If you have vacuum then the valve may be bad, a replacement is not expensive.

 

Great! Thanks, I will check that out. Should be something easy, I hope!

 

I saw you posted for a new vacuum switch, did you disconnect the vacuum line to the modulator there?

 

When I got the car back the guy had removed the DVCS and put a plug in its place. There's another port off the carb, that has a bolt in the vacuum line. Looks like the guy really hacked it. So I want to put it back the way it was. After you all suggested that vacuum could be a problem I'm thinking the shifting problem is probably in the vacuum lines. Once I get a DVCS and repipe the vacuum lines I'll test drive it again. Anyone have a spare DVCS I could buy? '71 455 NO wire terminals on top??

 

I had an issue where I had a non original TH400 that only had the kick down plug. The issue was the wiring under the car was a mess and the hot wire was plugged in and energizing the solenoid all the time like the pedal was constantly floored so the trans would do what yours is doing and not shift into 2nd until red line and never hit 3rd unless I wanted to try doing 100.
before you go all nuts with the vacuum, try disconnecting the kick down wire from the side of the trans and see what happens.
I had to ARGUE with the guy that rebuilt my trans and ended up having to unplug the wire in front of him to prove to him that was the issue.

 

I was planning to put straight manifold vacuum to the transmission tomorrow. If that doesn't help I will disconnect the wire from the trans. This car is pretty clean and almost 100% original. I owned the car for 25 years and sold it about 5 years ago. The guy who bought it died and his widow sold it back to me. So if disconnecting this wire does the trick what is wrong with the car? The kick down switch at the accelerator pedal??

 

If the TCS is still functional then you need to make sure the correct wire is on the solenoid for the kick down. It's easy to check with a VOM. The two terminals are in a T formation. The kick down one is vertical and the TCS is horizontal. Make sure the wire connected to the vertical terminal has no voltage when the pedal is not floored. If it does then there is a short in the harness somewhere. That was actually the issue I had and my harness was a MESS. I ended up replacing the harness and that fixed my problem for good.
You can also try disconnecting the harness at the pedal and see if that fixes it.

 

The rod inside the governor is not allowing the weights to move as they should. Pull the governor and clean with brake cleaner. Been there done that.

 

Thanks to all the suggestions. It was the downshift switch. It was stuck closed. Just ordered a new one. Thanks again!

 

Rock and roll. I'm glad it was an aleasy fix.