727 w/ transbrake

A friend has a 727 w/ a Turbo action transbrake valve body in it. When he stages the car and sets the transbrake, the car rolls forward slightly before it "sets". It releases and shifts fine, just won't set still. What causes this? Clutches slipping, loose band, too much end play, ect? All of the above? He hooked the line lock into delay box to release the same time as the transbrake and that seemed to be better, but I see that as a band aid. If the transmission (and valve body) is working correctly, he shouldn't need the line lock.
Thanks,
Brian

I was helping someone with a power glide once that was having the same issue.We was told to tighten the band some and that seemed to work.

Turbo Action suggests going into staging at higher rpm when setting their brake. A forward roll would be due to a delay in the high clutch engaging.
Doug

I have an A&A transbrake valve body and I use the line lock function in my delay box when the trans brake is engaged. Before having line lock function, if I staged at higher RPM, when I pushed the trans brake button, the suspension then relaxes and car would move a little. The Higher the rpm the more it would settle. Although it may seem like a band aid, I can tell you from experience it works very well. Many many racers with glides, th350 and 400s also use the line lock function. It helps a lot with consistent staging of the car.

The glide uses a band to hold the drum stationary when in low gear. If band adjustment isn’t spot on, it can cause issues. Like DVW said, the High clutch is delaying engagement if you’re not staging at enough RPM. Adjusting the front band in a 727 will have no impact on trans brake. If the valve body is low band apply (which I’m not sure if your turbo action valve body is), then the low/reverse band adjustment can have an impact if it’s out of adjustment. I know turbo action makes a trans brake valve body that doesn’t use low band apply.

Cycle the solenoid once, right before your final stage rpm increase. If he’s using a delay box, he might have to set the flinch time.

I have a TA pro brake. If I don't go in at a real fast idle, it won't set.

Yep, historically problematic with TA trans brakes...Back in the early 90's I used one, the reverse spool would stick so no TB, Higher pump pressure is needed to overcome the stiction. I don't know if they are still building them using Devcon as a way to modify the VB passages, but that is what attributed to the issues I was having. Would have to take the VB out and apart, and wash the "Dust" out.

Mine did the same so I’d engage a few time behind the line with delay box off then turn on box starts press button no roll. Also noted when first starting and moving forward it would lock a little, I did same procedure then. After the first time moving it didn’t do that again (maybe fluid had drained back some?? Might have to have at least12 springs in front clutch.

Just curious, is this a valve body issue or a transmission issue? Do all 727 trans brakes do this or only certain brands? Griners any better?

I had an A&A in mine and it never did it.

Valve body issue not a transmission issue. I have not had an issue with any of A&A trans brake valve bodies. I have not heard of CRT valve bodies having this issue either.

That is common for the Turbo action brake. It can be caused by internal problems in this case it is usually the valve body.
The Griner brake does not have that problem it sets up at idle. Keith

Griner Brake here , never did the roll after setting . Gary

I've never had a problem with my TranzAct.

Happened in my Mirada. New stator support rings and it was rock solid again.