200 4R No 2nd gear

[78anniversary]

Hello everyone, I understand this is the place to come for 200 4R problems. I have a 78 corvette with a 200 4R and it has no second gear. It used too, but recently lost it. I can get it to skip second and go to third and it works fine 3-4, lockup works, 4-3 downshift works, just no second. Its as if it is in neutral when it should be in second.

Everything I've read points to a band or servo problem. So i pulled the valve body, air tested the servo. I could get the servo to apply with air and could see the band applying also. I could turn the driveshaft while applying air but wasn't sure if that was normal due to the air gun not getting a perfect seal on the port.

I then pulled the servo and just reinstalled the pin and pushed on it with a prybar, I could also see the band apply when pushing on the pin with a prybar. I reinstalled the servo and cover minus the sealing o ring and pushed on the outer cover with the prybar and noticed again that the band was applying. I had approximately 1/8 inch travel on the cover.

What I am not sure about is if the band is applying enough. Could it still be slipping? From what little i can see of the band with the pan off, I can see friction material and don't see any burn marks on the drum. The fluid is also not burnt.

This where I am at now, not sure where to go next. Could there be anything else besides the servo or band?

Any help would be greatly appreciated

Brian

 

[TexasT]

Welcome!

You already know my thoughts

 

[bison]

What if you have a helper and you depress the cover and have them run the car with the wheels off the ground? The 2nd oil should push the cover back. At that point if you do have 2nd oil you could have any of the following:
broke band anchor
broke band anchor lug
servo bottoming out in case
wasted band/drum

It's possible the drum is undersize and the band butting as it applies too. It shouldn't take a lot of air to apply the band. Even 30-40psi of air will apply the servo and you shouldn't be able to turn the driveshaft. I'd investigate the things I mentioned above next



BPE2013@hotmail.com

 

[olds403]

Double welcome.......
If you can turn the driveshaft with the servo applied you have problems somewhere. Try a longer pin and reset the servo clearance. Worst case pull the trans and put on bench. Its not hard getting just to the drum/band. Just takes time.