Not a transmission guy so am at a bit of a loss here.
I swapped out my 2sp auto for a TH400. The transmission was used, in a friend's 69 bird. All I remember about it was that it ran like a champ and was very strong. It only had about 4,000 miles on it since rebuild, shift kit, some strengthening mods and a saturday night special torque convertor. I picked it up from him, dropped the pan and looked like brand new. He ran Royal Purple in it and I topped off with same after install. I have had it in the car about 3 years now with it running for the last 1. Have been driving it with no issues at all. 1st to 2nd gear is very strong, chirping the tires on cue. 2nd to 3rd is very strong as well but not as strong as the prior. Here is my issue. If I am driving along and manually shift into 2nd gear it acts like I am putting it into neutral. If I press on the gas, engine revs up to where it should be in 2nd and will accelerate just fine. Trans will auto downshift with hard acceleration at speed an does it with stamina. Downshifting into 1st is rock solid, even causing a small chirp in the tires on occasion.
Have not been able to track down friend as I moved across the country. So, any ideas?
Without driving it..only speculating. I have a Quarter stick in my car and swapped the valve body over to manual. I had similar issues with shifter not engaging all the way..
Also had vacuum modulator issues and sticking check balls manipulating shifts...
IMO..if fine while in Drive (automatic shifting) perhaps you could rule out the trans as the issue.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
Hmmm, not sure. Yes, In drive it drives absolutely great, My main issue with the problem is that it is pretty hilly where I live. I would much rather downshift into 2nd to slow myself down instead of having to ride the brakes all the time. I wouldn't think the modulator would have much to do with it but, like I said, I am not a transmission guy. I guess I was just hoping someone will see this and go AH!, Had exact same problem. I just did something simple and fixed it. Wishfull think'n I suppose.
Stall convertor? I know less than nothing about auto Trans but a higher stall means the Trans doesn't engage until a peticular rpm is reached, correct?
Depending on the modifications to the trans it can be that the transmission no longer has capabilities for engine braking. Which what it sounds like to me. So downshifting will no longer slow the car down.
