Orr89RocZ

iTrader: (20)

I have a question for all the transbrake guys with th400.

How hot does your trans fluid temps get while on the brake and how long are you on the brake?

I noticed an issue on my second outting at the track. I have what i think is an abnormal rate of temperature rise while on the brake which ultimately led to burnt fluid and now loss of first and second gears. I am only on the brake for 2 seconds it seems and my temps rise from like 110-120 at start to 260 at end of 1/8 mile pass! Its unreal. I didnt notice this last time out but i made 3 passes this second time out and just happened to see how hot it got!

Everything seemed fine til i let car cool down completely and went to go home. Put it in first and car wouldnt move.. Gave more and more gas and finally started moving. I thought i left ebrake on! Driving around it felt fine at speed in 3rd but at stops, i really noticed i had no 1-2 shift which is heavy on part throttles. That was no longer happening. Rpms never changed while moving 1-2-3 3-2-1 at speed.

Took pan off drained fluid. Fluid was way dark and burnt. But no heavy particles in pan. Just looked of burnt sludge.
Replaced fluid and still no gears.

Now i have a good reverse gear and tbrake still functions. It holds as rpms go up but when released it feels like its straight to third.
So what you think is wrong? Could it be a sludged up shift valve or something within the trans or valvebody? Or something break?

DIGGLER

iTrader: (1)

i have a trans temp gauge but never hooked it up. lol
i put mine on the brake for approx. 1-1.5 seconds each pass. i pretty much pushed the button at idle, and when the other guy staged i floored it. 2 step put the rpms around 3k as i waited for the tree.


how are you using the transbrake? do you have a 2 step set to a certain rpm? i honestly dont know how most people launch a turbo car. -something i need to learn!

project89

iTrader: (1)

sound slike its time for the trans to just come apart and be gone threw.
dont feel to bad atleast u got some use out of ur's, my th400/w brake had to come back out of the car after the first start , and go back to the builder

i also have a trans temp gauge but havent hooked it up , im going to add that to my todo list now

AlkyIROC

I stopped using a TH400 when I lost the transbrake and reverse. I tore the thing down 3 times and could not find the problem. I switched to a powerglide and never looked back.

All transmissions will heat up the oil when on the brake. They'll heat up the oil just doing a brake stall also. Oil temperature depends on where the sensor is located. Oil comes from the pan, through the pump, to the cooler, back to the hydraulic circuits then drains back into the pan. Anywhere along that path will have a different temperature. If you want to monitor temperature, the best place is in the pan since that's the start of the path.

Transmission oil generally runs hot when the transmission is working. Normally it runs roughly a little higher than the engine temperature. If the oil temp gets above 325*, it's getting critical and the transmission is about to fail. In the 200's isn't good for long periods of time either.

I use a 2-step, delay box and a starting line enhancer. As I roll into the starting beams, an air cylinder in the throttle linkage expands and my pedal falls to the floor. My foot is to the floor and the engine is at an idle. I push the transbrake button and wait for the tree to activate. I can sit there for minutes like that and all I'm doing is idling and waiting. As soon as I see the top bulb flicker, I release the transbrake button, the starting line enhancer fills the air cylinder with CO2, the engine goes to WOT on the transbrake. roughly 1.045 seconds later, the delay box releases the transbrake and away I go. Since the time on the 2-step with the transbrake applied is so short, I don't even bother with a temp gauge.

Solutions
Don't come up on the throttle until both vehicles are staged and ready to go.
Install a larger cooler. Tube and fin is not as good at cooling as a stacked plate design.
Use synthetic oil.

Orr89RocZ

iTrader: (20)

Use? This thing has less than 400 miles on it and only 4 1/8 mile passes and 2 full pulls, and only 20 dyno pulls. I am alittle pissed if it has to come apart again lol just done past fall.

I am on the brake for 2 seconds. I dont get on it til i am on 2nd yellow and dont leave til 1-1-1.2 seconds later according to my reaction times. I have a two step. Was 3800-3900 now trying 4400. Stall should be 4500-5000.

Turbos are in boost by then but rpm is limiting how much. I believe its 7-10 psi depending on rpm

DIGGLER

iTrader: (1)

who did the trans? i no longer trust any of the local yokals. i would send it to hughes/coan/fti or someplace like that.

Orr89RocZ

iTrader: (20)

Well know local who has a good track record

Orr89RocZ

iTrader: (20)

Trans was holding first pass lol

leeperryracing

i will be about 140ish coming out of the burnout box, on the 2 step/tbrake for about 3 or 4secs. At the end of the track, its around 195*.....but i do have a monster 15x10 cooler with a shrouded 7" spal fan on it, braided -6an lines.

Orr89RocZ

iTrader: (20)

Ordered an 8" fan. Holding off on twin coolers. Will see how fan works first

Fast 383

iTrader: (2)

Sounds to me like you have to go through that trans. Probably going to find clutches/steels smoked. Who's V/B? Pump will need to be checked for wear. Biggest issue with the T-400's is the 2nd gear sprag and drum set up. I believe you are probably past the breaking point of the 34 element sprag set up and should be using a bigger Pro Mod style 2nd gear. Don't be surprised to find that thing failed or broke the little snap ring off.

Before you do anything check your shifter linkage. Pull the linkage lever off the linkage and see if the linkage moves at all. If your shifter was out of adjustment it will lower the pressure and shorten clutch life down to about, oh say.... 400 miles on it and only 4 1/8 mile passes and 2 full pulls, and only 20 dyno pulls

Orr89RocZ

iTrader: (20)

Lol old post. Trans already rebuilt. No second gear drum or snap ring failures.
Just smoked the trans.