Put a TH400 with a 4400 converter and a trans brake... and you'll be ALOT FASTER than your 4l60e... Too many factors to decide exactly how much power you will lose... TH400 will not break unless you'll be putting a **** load of power through it...

J

 

what about if I don't use a trans brake? will the tranny alone make me any faster?

 

Also, you can't get a transbrake for a 4L80E. Well, you can but its about $600 vs $100 for the TH400. Rossler is the only company that I've seen make a transbrake for a 4L80E and it is EXPENSIVE.

 

What exactly is a transbrake?? I know it holds the car on the line before launch, but how does it go about doing so??

 

It locks the tranny via a valve, and forces the fluid to loop somehow.. it's like holding the brakes, but not with the brakes, makes teh car launch like you side stepped the clutch.

 

Here's a nice little right up on what the trans-brake does and why it is so effective:

"A transmission brake is usually considered a drag racing "only" automotive after-market device. It operates by simultaneously applying the forward and reverse clutch packs of an automatic transmission while its both in gear, and the torque converter is at or near it's stall speed. At the moment the trans-brake is disengaged the reverse element is released (usually the engine is revving at peak power) and the car will immediately lunge forward from its starting position.

You might wonder what the difference is between holding back a revving car in gear with just the wheel brakes versus that with a trans-brake. In order to understand this difference, more must be explained about the car's suspension, and how it operates during the initial take-off.

If your car has a rear-axle drive with a solid suspension, it most likely also has what's called "anti-squat". This term defines the function of the rear suspension geometry that prevents the body of the car from "squatting" during it's initial acceleration. In fact, the rear of the car will rise if the anti-squat factor is high enough to overcome the inertial forces encountered during this initial acceleration. Many cars from Detroit incorporate an anti-squat design in order to prevent suspension "bottoming" during initial acceleration. You can find out if your car has this feature by performing a simple stall test and if the rear end rises, it has anti-squat. If your car has an independent rear suspension, such as the Corvette, it will squat because this type suspension has a "pro-squat" type geometry built into it.

How is the trans-brake and the rear suspension related? Keep in mind that for every force in one direction, there is an equal and opposite force in another. The force that is opposite to the raising of the rear will appear as high instant tire loading during initial acceleration. Its instantaneous because this force only occurs at a moment during the initial launch. This at the time between when the car is at rest and when full power is being transferred to the rear suspension.

Since the traction forces of the rear tires usually increase relative to their contact patch force, a car having more anti-squat will always have a higher acceleration and therefore will launch much quicker. If the wheel brakes are used for staging, the rear suspension becomes preloaded and all the anti-squat factor is already used up. When a trans-brake is used for staging, the rear suspension remains at rest and is unloaded. At the moment you flick the switch and release the trans-brake, the immediate transfer of engine torque "shocks" or loads the rear suspension, performing as it would with a stick-shift car. The trans-brake also prevents the high-powered/high stall car from overpowering its brakes on the line. By comparison, the trans-brake release action is much faster than lifting your foot off the brake pedal (or even a clutch pedal for that matter).

The trans-brake is used in conjunction with a specially calibrated full manual valve body. During operation the transmission will function normally, even if you choose not to use the trans-brake. A toggle switch is used to simply turn off its operation. Since the trans-brake is an added feature, the operation of the transmission can not be adversely affected when it is not being used."

Dan

 

I made 460 rwhp N/A on my old setup with a mild built MTI 383, 6spd, 3.42's and 390 rwhp with the TH350, 4000 stall, and 3.73's. Track results were 2-3 tenths faster with the A3. My car hated the dyno. LOL

 

damn thats a loss of 70 HP~~

 

Some of the loss was changing from 3.42's to 3.73's. But it was kind of sickening to watch my buddies H/C GTO after me dyno 400rwp on the same dyno, but I made up for it later when I outrun him by over a second at the track.

The MTI dyno wasn't showing torque that day, but judging by the hp curve there was quite an increase.

 

How is that possible, when a dyno measures TQ and not HP?

HP is simply a calculation taken from TQ and RPM. If you don't have the TQ, you don't have the HP.

 

I don't know why. I went there twice and Jason couldn't get the torque to show on the graph either time. I think in order for the computer to print the tq curve it has to display rpm, which the cable that goes on the plug wire wouldn't read.

Here is the graph: Dyno Sheet

 

Try the same test on a LOAD dyno which is a much more accurate measurement for simulating road/track wheel power and see what happens. I guarantee a before and after comparison from 4L60 OR T56 TO TH400 will show a much much smaller loss and be accurate to what the numbers really are. I did this about 5 years ago when I first swapped from my 4L60 to TH400 and the difference was less than 5%. I also picked up .3 in the 1/4 and gained 1.5 mph with no other changes.
I sold the car shortly after that and have just bought it back from the guy I sold it to. He installed a 4L60E again so Im about to pull it and install a 4L80E that I ordered from GEAR STAR / YANK so Ill have some numbers for that swap before the end of the month.

 

I believe dynos measure HP and then calculate TQ. Given the drums weight and circumfrence it's possible to calculate the amount of work done over time.

 

Wrong, again, HP is simply a number we get from a calculation - it is not a measured number.