[Tim]

Who can tell me about trans brakes? I kow they give you a kick- ass launch, but what are they and how do they work?

Could you use on in a street driven car?

I'm only asking 'cos I don't know.

[dave-r]

As far as I know they work by locking the transmission so you can rev the engine up to the stall speed and then release the trans. A bit like holding the car on the brakes with your left foot. Only better because there is no chance of overcoming the brakes and it releases faster than lifting your foot would.

[fbernard]

but what are they and how do they work?

Could you use on in a street driven car?

I'm only asking 'cos I don't know.

Basically, they work by applying both rear and front band when activated(that prevents any driveshaft motion).
I guess They could be used on a street engine, after all, you don't have to use the transbrake feature at every traffic light.

The only drawback being, once your car is so mean you need the transbrake, and once the car is modified to take advantage of it, the whole deal is no longer a street car...

[Tim]

Thanks for the feedback chaps.

Is the thinking then that your thumb releasing a button would be quicker than your foot lifting up off the brake pedal? Or is it that the mechanical linkages would react quicker through a transbrake?

Or both?

I get the impression, these devices only really work well with very high stall transmissions, which as you say would render the car next to useless for the street. But could you theoretically use a trans brake on a lower stall car, say 3200- 3500 rpm? And if so, would there be any point?

[drewcrane]

people use the line lock(brakes), for burn out, and the the trans brake for a high rpm launch, you better have every thing tight, as i have see plenty o cars give out when that trans , lets loose as you can imagine not very practical on the street, as it aparently uses the reverse/forward to get to stay still while revving to say 3 grand, the hit the button and whoosh you r gone, i have only see it on serious drag cars,not any street cars,just a brake line lock , for like i said burn outs

[fbernard]

I get the impression, these devices only really work well with very high stall transmissions, which as you say would render the car next to useless for the street. But could you theoretically use a trans brake on a lower stall car, say 3200- 3500 rpm? And if so, would there be any point?

Of course you could use one with a friendlier converter, but what would be the use? You can foot-brake even a 4500 RPM converter.

The reason for the transbrake is simply bracket racing reliability : it's easier to achieve the same results, repeatedly, if you automate as much of the whole process as possible. Lifting your finger from the transbrake button is almost a binary process.
Lifting your foot from the brake pedal isn't.
You can even find setups where the driver releases the transbrake as soon as he sees the amber lights, and the Transbrake+rev limit deactivation is done through an electronic timer to work on the RT.

Think about the strain a transbrake puts on parts : the obvious conclusion is that you need a really big driveshaft, and a spool. A 2-stage rev-limiter is mandatory (or you manage engine RPM with your foot, which just about negates the repeatability factor. a triangulated 4-link or ladder bars also help assure that suspension travel is identical at every run.

In my opinion (but I'm absolutely no expert), the transbrake is one of the last steps on the road to street-unfriendliness...

The only cars I know in France which have a TB are all trailered to the strip.

[drewcrane]

TB are all trailered to the strip.,cause they can break , and leave you stranded at the track!

[transman]

Tim a transbrake on the street is not really a good thing. The transbrake typically puts your transmission in low and reverse gear at the same time when you push the transbrake button to activate a solenoid. There will be no forward movement of your car. They are designed to allow you to rev your engine up to the stall speed of the converter you use to take advantage of the horsepower and torque the engine is making.
For a poor example, lets say you've put a properly matched 4000 stall converter in your car and head for the drag strip. You've got your big sticky slicks on the back and those nice light weight skinny tires and rims out front. Once staged, you step on your brake pedal as hard as you can and start to apply some throttle. All of a sudden, what the heck? The car is moving forward, or the rear tires start to spin. Why? I've got this great loose 4000 stall converter and the damn thing wants to move the car long before the stall speed. Why? Your brake system is typically not capable of holding back all that horsepower and torque. Now put in a transbrake. At the line once all the stage and prestage lights in both lanes are on, apply the transbrake button (on the shifter, steering wheel or wherever you put it) and now with the trans locked in low and reverse, you can take full advantage of the converter and engine. Bring the engine up to the stall of the converter, and on a protree, when the orange lights flash, release the button and away you go. On the non pro tree, release the button on the last orange and boom, you're gone.
Transbrakes were designed for one purpose, drag racing. Put on in your street car and you'll always have to manually shift the trans as there is no more automatic shifting on the ones I've seen, and you'll have a reverse shift pattern. It will be P R N 1 2 D not P R N D 2 1. Fun, yup, but I don't think so on the street.

transman