I have an A&A brake and I decided to chip up to hit the 4 link harder and got a surprise. Always launch between 3000 and 3500 and everything works well, as soon as I went to 4200 the transbrake wouldn't hold, pushed right through the tree.Went back to pits and put a 3500 , worked fine, in fact 3800 worked ok, put the 4200 back in and wham car took off on the 2 step. Ran the rest of the day at 3500, no problems. Small block with 904, 8 in PTC convertor and stalls 5000 in high gear. Any Ideas?

check your alternator output..
voltage drops can cause this..
when i hot lap..if my batt isnt up..
i get t-brake issues..
fwiw.
cheapst.

If all those check out you might check line pressure I think it should be 130 - 145.It is on my tranzact.

I did check alternator and it was putting out 13.6 volts and batteries were fully charged right before that pass. I too was wondering about line pressure or rear band. At the Chrysler Classic on Friday morning a couple of weeks ago, Transbrake acted same way at 3500 rpm but the clutches let go on it. Put in this back up trans that had about a season on it, and my first thoughts were that sickening feeling that it just did it again. However fluid looked good, and it worked well for the rest of the short day,(5 passes)lol

Dan
I had a similar problem and it turned out to be part of the front pump gasket had pushed through and caused an internal leak and would not let the brake hold when I went against the 2 step. the car would back up fine and would hold at a low RPM. The problem sounds very similar to the problem I had. Check your line pressure.

Jack

Thanks Jack, If I get time this week I'm gonna rebuild the one that gave out at the classic , But I am gonna check line pressures in this one before I pull it. See, I was just bragging about getting 2 seasons out of a 904 and it came back to bite me.lol

Do you have the Tranksbrake hooked to the linelok?

I had same problem with a clogged filter.
Again with a band out of adjustment.

IDK
But your car sure looks fimilar, ever run at Blue Grass Raceway Park in Ky?

Check your ground to the transmission. Put your car on jack stands and check the voltage at the brake when engaged. Much safer if you have a removable tunnel where you can do this at the top of the trans.

The high gear clutch pack is the only thing extra, that is
engaged during the trans-brake activation.

Worn clutches or leaking seals is where I'd look first.

But your car sure looks fimilar, ever run at Blue Grass Raceway Park in Ky?
Yea We have been there a few times, go down and race with Clancy Keaton and Rob Lawson. Rob is John and Laura Lawson's uncle so we used to go down with them.

Actually the Cuda has been there more, here is a pick of the Cuda .It's my son and Laura Lawson. He won , she runnered up in her Challenger. Since He dialed both cars, He did have a little advantage, lol, at least We tease Him about it.