What is a trans-brake, how does it work, vs line-lock?

Discussion in 'Technical' started by scooper77515, Jun 12, 2005.

  1. scooper77515

    scooper77515 Accepting Hand-me-downs Supporting Member

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    My title says it all.

    What is a trans-brake, how does it work, and is it better than or comparable to a line-lock, and why?
  2. stockhatch

    stockhatch Re Member

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    Transbrakes engage clutches in a transmission in a way that locks the transmission against itself so the engine is loaded and the converter can flash. AFAIK its better than line lock because the drivetrain is locked as opposed to just brakes which can be overpowered by the engine.
  3. Old Guy

    Old Guy Member

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    Trans brake is a solenoid operated valve in the trans valve body. It essentially locks the tranny in foward and reverse at the same time until the actuating button is released. Really puts a shock on the internals but is instant engagement of foward gears. They are also used mostly with other electronic devices, for quicker reaction times and consistency in et's. Line lock is also a solenoid but is installed in the hydraulic brake line, to lock up the front brakes for burnouts and some even use them on the rear for launching(never seen them work for that to well). They are button or switch operated too, but only releases the brakes and has nothing to do with the trans.
  4. tim keck

    tim keck truckdrivintrailertrash

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    Use a line-lok on a streeter,much cheaper & easier on parts.
  5. mavman

    mavman Member

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    Line lock is for burnouts and burnout contests. Transbrakes are for race cars.

    The main purpose of a trans brake is so that a driver can mat the gas at the line with the transbrake engaged, and the car will not move. When the button is released (and a delay box is not used) the car is already wide open and it will instantly go. No waiting for the throttle to open, secondaries to come in, timing to advance, etc...it just goes. Also, they're more consistent than just footbraking at the launch...The driver's eye-foot coordination is worse than eye-hand coordination, plus with the use of a delay box you can get near perfect reaction times consistently and easily (yes, "box" racing is easier than footbraking!) as releasing the button and ultimately "unlocking" the transmission is much more consistent than having to push the throttle down, release the brake and steer all at the same time.

    Don't try a transbrake on the street..unless you have slicks. It just blows the tires off instantly. Used to know a guy with a '77 Camaro with a 509 BBC/powerglide with transbrake that would play around on saturday nights on the streets. It'd come up on the converter (5000 stall), light turns green and he'd release the button...and tiresmoke was almost instant, as was the 7000 RPM limiter. No wonder the motor didn't last long!

    Line locks were originally designed for standard-shift cars so that they wouldn't roll through the lights at the starting line while the driver had one foot on the clutch and one on the throttle. I remember how much of a challenge it was driving my old Mustang 5 speed without a line lock. Good thing I wear size 15 shoes...makes it a little easier to hold the brake and gas with the same foot.
    Last edited: Jun 12, 2005
  6. don graham

    don graham MCCI State Rep Supporting Member

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    transbrakes are essential in certain classes of racing. just make sure you have lots of spare parts and money.:)
  7. scooper77515

    scooper77515 Accepting Hand-me-downs Supporting Member

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    The transbrake sounds like it would be hard on internal transmission parts, as well as other driveline parts. For a daily street driver, I think I will install a cheaper and less invasive line-lock.

    Line lock will free up my rear brakes for burnouts. How hard on brakes is a burnout? It seems that some of that smoke should be brake-shoe heat and powder. Does burning out with the brakes on lead to, not only shoe/pad wear, but warped drums/rotors and other permanently ruined brake parts? Or is it just as much wear as coming to a complete stop 5 or 6 times from 70mph?
  8. don graham

    don graham MCCI State Rep Supporting Member

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    i've been doing burnouts with my brakes for 7 years now and no problems. but they don't get any additional use on the street.:)
  9. igo1090

    igo1090 Member

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    the line lock only locks the front brakes when set up for heating the tires. shouldnt bother the brakes at all. trans brake is hardest on the converter & the fluid, but also the axles, gears, tires, etc. also doesnt lock the front brakes, so the car can move forward when tires grab. you should also be off the throttle when the tire do grab, or bad things can happen inside the trans to the sprag, etc.
  10. Old Guy

    Old Guy Member

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    As Don said, holding the brakes on with your foot is probably the most used way of doing burnouts. However, it sure puts some wear on the rear shoe's as the torque overpowers the brakes to spin the tires. Is not an issue with moderately fast cars, but those pads or shoe's stay hot all the way down the track and on very fast cars, could cause a problem. Line lock on fronts is my choice, even for my turd of a race car. The trans brake release is only used for launch and is compared to holding your foot on the gas, wide open and then sliding your foot off the clutch on a std. shift car. Better have good tranny to take that abuse, and just for info, when you are on the start line and watching the tree come down, you are holding the gas pedal wide open and never letting off. Just releaseing the button and with or without a delay box, crossover, etc, the car should shoot out of the box like a rocket, Most are launched at 6500 to 8000+ RPM's, some even higher. They are useless on the street and very dangerous too.
  11. bmcdaniel

    bmcdaniel Senile Member Supporting Member

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    Also when used for drag racing a line-lock allows the rear suspension to be preloaded when the car is staged, ready to spring when the button is released. A trans brake doesn't apply power to the rear suspension during staging so when the trans brake is released the suspension is "shocked" and has to use a small amount of time to "wind up".
  12. scooper77515

    scooper77515 Accepting Hand-me-downs Supporting Member

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    So, with the stock 1800 stall, and a line lock. Do I lock the front brakes and rev to 1700-1800, just before the tires let loose? Then let off at the light? Just like I currently do, except the rear brakes are not engaged?

    How is this going to be different than my current launch.

    Actually, with my current configuration, I don't make it to 1500 or so before the rear wheels start to break loose from the brake shoes. Slowly at first, but then the rear end starts to swim, usually to the left (mini spool spins both tires, right gets more traction from engine torquing that side downward, pushes car to left). If I really mash the brakes, the engine revs to 1800 and stops, hence "stock stall of 1800". Am I right on this.

    Sorry to talk about "stall" on a car without a stall converter. May offend some of you more race-oriented types.

    I am new at this. I will get there with time.
  13. Old Guy

    Old Guy Member

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    Just my own opinion, but in your case I would forget about using the line lock for starting line launch's. As you have stated, usually the tires will start to either spin or in most cases, grab and actually shove the locked front tires foward. Use it for burnouts only while the tires are wet from the water box, and then as they heat up and begin to grab the track surface, release it and pull up to the line. Foot brake it and stage the same each time, practice getting good lights and watch the 60 ft. times. When they become consistent, you are becoming a good drag racer. If the car wants to walk to one side on burnouts, is normally because you did not get both tires wet enough and one is trying to bite as the other is spinning. Or if it is walking at launch, may have to much preload on one side or the other as you stated. Lots of crap to figure out, but I think you have a pretty good handle on it for being a bit new at it. Stall is another whole subject and you should not worry about it till you get the basic's figured out for good staight launch's and reaction times.

    Reminds me of a very young bull and a very old bull. standing on a hill overlooking a herd of cow's. The young bull says " Let's run down there and mate with one of those cow's" The old bull says, "Lets walk down there and mate with all of them" Patient's has it's virtue's, so they say.
  14. ShadowMaster

    ShadowMaster The Bad Guy

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    It's important for you to understand the term "stall speed" as it pertains to your application. Stall speed is relative to the amount of torque the engine produces. Example: A 10" converter advertised at 2500 stall speed may only stall to 1500 when applied against the foot brake behind a 302" engine; the same converter behind a 351" engine will stall higher (say 1900) due to the higher torque produced by the larger engine. Another point to consider: a transbrake will allow you to 'stall' the converter to it's highest possible point by locking the transmission in low/reverse. This lets you use all of the stall built into the converter. If you do not use a transbrake and you are "footbraking" the car, you will see a much lower point at which the car wants to move. Adding a line-lock will NOT change this. A line lock is used for burnouts and staging....not for holding a car against the converter.

    I am a staunch supporter of transbrakes for street/strip and race cars. My '98 GT has a transbrake and I drive her everyday. My son's Futura has a transbrake also.....takes him back and forth to school/football practice and to the track. Bottom line? You don't use the transbrake on the street for launching. After all.....you only race at the track....RIGHT?!?!?!?!? Using the footbrake at the starting line is ok if you don't have the money for a transbrake. If you can afford one....get it. It is not harder on internal parts either. Also....ever notice how the car tends to "load up" against the suspension when you are using the footbrake? Once you release the footbrake the car has to transfer the weight back down to the suspension/tires and then it launches. More distance for the suspension to travel. With the release of a transbrake, you "shock" the suspension into action. The car leaves quicker which equates into lower elapsed times. Lastly, a transbrake valvebody is no harder to install than a cheap shift kit. In some cases it's easier.
  15. 74merc

    74merc computer nerd

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    I know it varies from car to car, but every one I've played with ran slower holding against the converter with a foot on the brake. Just initial flash of the converter hits a higher RPM and you start rolling, better weight transfer, better engine acceleration, stronger neck snap during takeoff... See what works for you before buying parts that may not make a difference.

    Transbrake is a different beast... haven't messed with one yet.
  16. mavman

    mavman Member

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    Not all of us have $600+ for a transbrake for a C4.

    Yeah it is. C4s usually don't last near as long when using a 'brake. Neither do Powerglides. Puts a TREMENDOUS strain on the shafts and clutches. Remember the torque converter's torque multiplication? Well...at a 2:1 TM, that means if your engine makes 300 lb-ft torque at converter stall speed, the trans is seeing 600 at the input shaft. Then consider that a C4's low gear is 2.48, you're putting 1488 lb-ft of torque against the high clutch when the brake is applied, also the same torque goes to the gearsets. It ain't gonna last forever like that. Not to mention the extreme heat built up inside.

    With the footbrake held, the suspension is loaded...and the car reacts quicker. I proved this to myself a long time ago....by watching a vid of my car launching. That's how I actually can scrub off a slight amount of ET if I know I dialed too tight...a little less RPM at the launch and bumping in a bit further.

    Yes, the transbrake releases reverse gear, and shocks the drivetrain. It also tends to be a little rough on driveshafts, gears, third members, chassis, and everything else driveline-related. If you have a car that traction is marginal, it won't pick up that much, if any. I know that on my car the transbrake doesn't pick up ET at all...MAYBE .01 on a good day/night, but that is negligable considering the shock that the drivetrain takes. And yes, the Transbrake valvebody is easy to install.....actually, it just bolts in. Putting the solenoid on and running wiring is a challenge sometimes, and modifying the case (if needed) can be a bear if you don't know what you're doing (like backyard guys like me!). Also, a GOOD wiring job has to be done for it to work right....skimp on the wiring and the solenoid won't hold, and a red light is almost a guarantee. Keeping the internals of the transmission in tip-top shape is paramount. Any slippage in the high clutch (C4) or low band (also C4) will cause the car to roll when the 'brake is engaged and worse...if that multiplied torque makes it's way back to the one-way, it can explode....ever seen a sprag let go? It ain't pretty. TF727's are notorious for that, and they were exactly the reason that trans shields were mandated! They literally rip a gaping hole in the floor and fill the interior of the car with hot trans fluid, parts, springs, rollers, sometimes the shaft will bend and continue to swing around inside the car at thousands of RPM.

    Transbrakes are great, but you had better be ready to take on some expenses. I would suspect that a 'brake C4 could easily set a man back $2000 all said and done (with converter)...where we've been running stockers for years, pulled from scrap metal recyclers and rebuilt with a good manual valvebody...total investment under $100 minus converter. Bottom line is that if you want to race, they're fine....but they don't always pick up that magical full second of ET that you're sometimes lead to believe! Like I mentioned before, they're great for cars that need to leave quickly (.400 pro tree racing) and fine for bracket racing....on a heavier car that needs the 2.46 low gear (or 2.48...whatever it is, cant' remember) to get it moving. The primary purpose in brackets is to just keep the launches consistent from round to round...NOT to improve ET. In fact, most times it doesn't improve ET. On a heavy car with a too-tight converter, yes, it may pick up a little. Not always though. I didn't want to start a pissing match here, but I feel that all the information that one can gather (especially real world information...like what we've done over the years) can be very beneficial. After all, what good is knowledge if you don't share it (or if it gets exagerated a little)?
    Last edited: Jun 15, 2005
  17. 74merc

    74merc computer nerd

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    Educate me a bit here. I never understood the torque converter to multiply torque x2. How is this? I understand essentially as the converter slips you get more rpm crammed into the input vs output, so a little torque is gained.

    As I've always figured it, torque gains by the converter are limited, torque multiplication comes in gear, 300lbs torque x 2.43 (I *think* its 2.43, 1.46, 1) so 729lbs of torque to the rear of the tranny, or front of the gear set when under transbrake... gotta learn more about trannies.

    Bottom line, 300lbs torque with a C4 and 3:1 gears puts 2187lbs of torque to the rear wheels, not accounting for 20% drivetrain loss. If the converter multiplied torque x2, you'd be putting over 4000lbs of torque to the ground with a warm 302, which should be more than enough for a good wheelstand with traction, and most people can't do that.
  18. Andysutt

    Andysutt '72 Comet GT

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    Not arguing over anything here, as I don't know much about transbrakes.
    But i do know they just help you leave earlier if you know how to use them right.
    ANyways, reason I posted was the ratios are 2.46, 1.46 and 1:1
  19. 74merc

    74merc computer nerd

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    I have no experience with transbrakes, so I don't have a comment on them. Holding the foot brake to stall has always made launches slower for just about every car I've worked on and played in.
  20. CometGT1974

    CometGT1974 Gearhead

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    Man, I can't believe I missed this thread.....

    Listen to Mavman, transbrakes are definitely hard on stuff and they create a tremendous amount of heat in the tranny. Any reputable builder will tell you that if you plan on transbraking it a moderate amount, it will need to come apart once a year (usually at the end of the race season) and need to be looked at and possibly freshened up. Of course, that all depends on how many passes you make in a season and if you do any street driving.

    I've transbraked my C4 probably 50 times this year with plenty of street driving and there are no signs of any problems from the trans but it will be coming apart soon to be inspected and checked for wear.

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