Trans-Brake

[MCummings]

I know there are a handfull of transmission builders here at TDR.



But I have a question about How does a Trans-Brake Work?



I know they wouldn't be to practical on a Turbo Diesel, because you couldn't spool up the Turbo by holding the brakes, and the "Go" Pedal.



BUT I do Have a Chevy 350 with a TH400, a Reverse Shift Valve Body and Transbrake.



A few things I know about this TCI ValveBody and Transbrake, is that it will hold the truck still, let you rev up and act like "Popping" the clutch, or dropping it in gear without damage, and to Engage reverse you have to put the transmission in neutral and "Push the button" (Engage T-Brake),, If ya put it in reverse "gear" ya can severely damage the transmission.



So, How do these things REALLY work? I know they are a solenoid of some sort,, atleast that's what it sounds like.



Anybody got the beef out there?



TIA,

Merrick Cummings Jr

 

[24vcummins]

I'm by far no expert but, if I'm not mistaken, when the transbrake is engaged, both forward and reverse gears are engaged which holds the car in place. Release the button and reverse is released. I think it has to do with the routing of the trans fluid. Probably not much help.

 

[Jim Fulmer]

Merrick It's just like said up above, it's just a fluid route thing, hold reverse and first together, let the converter do all it can then let reverse go... . simple.



Jim

 

[Strick-9]

Merrick,



Oh contrar! A trans brake would help out turbo vehicles tremendously. You CAN build boost while stopped and on the go pedal. We ALL do that at the dragstrip. Stomp the brakes, build 10-30 psi of boost and let 'er rip.



There's a few threads going right now asking about transbrakes.



On a power glide, an extra solenoid is screwed into the back of the case. This solenoid feeds the reverse clutches when activated. Just like everybody mentioned. You pull the transmission down into 1st and hit the transbrake button to apply reverse as well. When you release the button, off you go.



Our trannies are a little different because we don't have a reverse clutch pack.



On our trannies, the clutch pack applied in reverse is also applied in third gear. So if you simply fill the front clutch with fluid via solenoid, you will start off in third gear. On our trannies, you have to fill the front clutch and also apply the low reverse band. This would require you to physically pull the shifter down into 1st and manually shift out when you want second.



That's how the drag cars running 727's have to do it. But they all run manual shift valvebodies anyways.



I'm not one to preach on safety. But I can't comment on this thread without saying something here. The 47RE was never designed to work with a transbrake. They were never designed to handle 1500 ft-lbs of torque either. Combining those two will be a lethal combination. Building a transbrake is easy, but without a blowproof case it would be stupid for someone to do it. The trans will explode, literally. It will come through the floor and amputate feet and legs. It's not a pretty sight. It does happen at the race track on occasion. So please be careful. It's simply not worth the risk for any of us.



-Chris

 

[MCummings]

Thanks Guys,, Really appreciate it.



My "Drag" truck from the dark side (Gasoline V-8) should be done in time for my birthday,, then I can try the trans-brake in a real world application.

The truck only needs a shifter cable hold down bracket, but gotta wait for the weekend to be done with.



Thanks a bunch

Merrick Cummings Jr

 

[Jim Fulmer]

The trans will explode, literally. It will come through the floor and amputate feet and legs. It's not a pretty sight



I've seen this very thing with a 727, luckly all that happened was the metal in the floor was rolled over his foot..... next transmission was a glide! I have to agree with Chris, transbraking one of our trucks would be nuts, but so is sled pulling without scatter shields.



Jim