Hey guy's I posted here a while back and thought I had found the problem with my trans. My sprag came apart when the rear end broke eariler this year so I ordered another one and put it back together. The darn rear band was applying when I shifted the car into third gear and gave it gas. The harder I reved it the more it would apply. Pulled the transmission back out replaced rear band and drum , found a couple of bolts for the valve body striped into the case. Replaced bolts and put it back together. It worked great. Thought it was fixed. Took the car out the other day for a long drive and after it got good and warm it started to lock the rear drum again. I could let off the gas and it would release and run fine but every once in a while I could feel it try to engage. Valve body maybe ?? Any ideas ?? Thanks,

There's a part of the VB transfer plate that I call the "mushroom", the part that covers the accumulator. Any surface irregularities in that area (warped plate or case, divots in the machined surface, etc.) will allow fluid pressure from the front servo/accumulator to crossover and apply the rear servo.

Check both surfaces for flatness and be sure the four bolts on the mushroom are tight.

I will do,, Thanks. No mechanical problem would cause this would it ??

I cleaned and checked the valve body today. It won't very dirty inside. I don't see any places that may have leaked fluid to the servo. Is there any other things I should look at ??

how did you set the band adjustment?

I tighten the band adjuster up snug and backed it off 2 full turns.

How do you know the problem is un-commanded rear band application?

In a non-transbrake VB the only way the rear band can apply in 3rd is if the servo is energized with fluid pressure when it's not supposed to and that is most often through surface irregularities. Check the case/VB surfaces with a good straight edge.

The pic below shows the close proximity of the rear servo apply port to pressurized fluid from other sources.

Hey John. I see what you are talking about. I will check the level on the case. I can tell it's sending pressure to the drum because it has actually turned it a little blue from applying. I check and it didn't hurt the band but it was sure wearing it out quick. I know just enough about transmissions to be dangerous , so thanks for any input..

Another possibility, instead of applying when not commanded, it might be dragging due to improper adjustment or the piston cocking in its bore when released.

I thought that too. but have rechecked the adjustment and the piston works fine with air pressure. Second darn time I have had it apart. The first time it hurt the band and drum. This time I caught it before it damaged too much.

Just thinking out loud, which bolts were stripped and what was your method for repair? Maybe a crack in the main case allowing fluid to crossover?

I repaired them this time with Heli Cores in the case. I will check on the case and see if any cracks are noticeable. I sure hope not ..