89formula#1

Hey guys I am thinking about building an auto trans for my car as sumthing to do this winter and as a learning experience.. Now I am going to want a full manual valve body and a transbrake so I can leave the line at a higher rpm then my stall. Now is one of these transmissions better to have with a transbrake or it doesn't really matter?? I will probably get the kit from Probuilt to build it if that makes a difference...Also are the ratios much different on the 400 then they are on the 350 and whats usually better in our cars with 3:73's and a 26 inch tire?? thanks alot everyone

cheyenne383

iTrader: (7)

The TH350 is lighter internally and more efficient. I would go that route if it was my car. The TH400 is marginally stronger when equally equipped, but the 350 will be a good bit faster.

IHI

iTrader: (1)

Depending on the amount of power your running, A TH400 equipped tranny is the only way to go IMO. There are ver FEW guys running t-braked TH350's and there is a reason for that. To build a TH400 that is bullet proof and can take the punishment $1K will be about your minimum investment then add on the frivilous like the big cast pan, big trans cooler, temp gauge, seriously consider running -8 or -10 lines into the tranny.

It's your coin, but the 350 internals are wekaer by design and even getting the best stuff offered for the 350 it will still be weaker than a marginally prepped TH400.

T-brakes are the best improvement you will make for bracket racing since so much can be adjusted with rpm chip in your 2 step and now you can acutally make the chasis of your car work like it's supposed to-alot more consistent overall. You will note as I have there will be alomst no difference in ET/mph between footbraking and T-braking. I did multiple passes with multiple chips in the transbrake and different rpms foot braking and all were about the same at the other end of the track-basically it all comes out in the wash so to speak, but the consistency is what you should be concerned with anyways. It will drop you 60' time sticking a big pill in your 2 step, but wont gain you much on the other side.

RB83L69

A trans brake works by shifting the transmission into 2 gears at th esame time; and by letting one of them go, to launch the car. Usually you want low and reverse, and you let it out of reverse to launch. A 350 doesn't work that way, though; low gear = the low-reverse clutch by itself, and reverse = low-reverse plus reverse; so if you shift it into low and reverse at the same time, you get .... reverse. It therefore has to use 3 gears at the same time to create a brake, because the low clutches plus the intermediate clutches = 2nd gear, and low plus the high clutch = 3rd gear. So a 350 doesn't make the best choice for putting a brake into.

89formula#1

Well my cars stick right now and the higher the rpm i dump the clutch at the faster it goes in the 1/4. Now maybe my understanding of a transbrake is wrong, I think that with a trans break u can have a 1200 stall converter and hit the transbrake and rev the car to what ever rpm you desire liek say 5000 then let off te button and launch. Now am I wrong here? does the trans brake only let you go to the max stall on the converter?? juist without any power to the wheels at all?? thanks for the lesson guys...

IHI

iTrader: (1)

That's exactly what a trans brake allows-it lets you go to against the actual stall speed of the convertor if you wish. Simple test to know what your actual true stall speed is with a T-brake-pull the chip out of your 2 step for the starting line rpm, hit the transbrake button then mash the gas and see where the tach stops. It does not allow you to stall 5K on a stock convertor, it allows you to go max on the actual stall speed.

If your running heads up for fun or just pulling the front tires it's fun to go max rpm, but for actual bracket type racing you will find it impossible to do this in eliminations since you will probably go red everytime and traction also starts to become an issue-especially in the summer months when the tracks get greasy. Ex. regular .500 sportsman tree I use a 3000 chip for staging and cut .50?-.51? lights, with a 4600 chip in I'm deep into the .430 range. Even when racing open comp races on a .500 pro tree I still have to use the 3000 chip since I go off the last yellow anyways, otherwise with a 44-4600 chip I'm consistent .430-.440 red on the pro tree. But then with my usual 3000 chip on a .400 tree I'm .560-.600 - I dont do that type of tree enough

89formula#1

so you have to have a 2-step to use a trans brake?? Do you think with a Th-350 from probuilt with the manual valve body and liek a 3300 stall I will pick up any time in the 1/4 over the stick?? I went 12.70 at 107 with a 1.7 60foot leavin at liek 4100rpm... thanks man, also with say a 3300 stall I coudl leave at wha liek 3000 prob?? thanks again

IHI

iTrader: (1)

I've heard both ways on faster/slower, no first hand accounts with the group of guy I race with, and I'venever really brought it up. Only thing I can say is for a bracket racing the auto will be hands down more consistent and give you a shot at winning races/cash.

You dont "have" to use the 2 step, but in reality it goes hand in hand with it. Basically it's the one thing that gives you control over the situation from a tuning standpoint, and for what your going to wrap up getting the tranny set-up, the 2 step components is a drop in the bucket so to speak, when comparing $1000 the $120 for the module and pills is pretty small.

If your stall is rated at 3300 and everything in the convertor matches engine output you could easily leave at 3000. I have'nt done the no chip on mine yet to test actual stall speed, but the convertor is rated for 4600 and I've installed a 4800 pill once and got away with it. I dont have a monster tach with playback either so right now it's impossible for me to watch and see where it goes. After I let go of the button I have to pay attention to the lanes and the shift light to nail the 1-2 shift since it happens so fast outta the gate, so I dont really start gawking around until I pull third gear.

FWIW, after I installed the taller tires my 60's dropped to 1.53/.54 leaving at 3000 on the t-brake. When I installed the bigger pills-typically 42-4400 the 60' would only drop into the 1.51-.52 territory so I did'nt see any real gain other than pulling both front tires inistead of just the drivers front like I do on race day. Footbraking dropped it into 1.57/.58 territory leaving with the car at a dead idle for 2 passes, then leaving with the cars chasis preloaded footbraking at about 3000, but the ET were about the same, mph picked up when footbraked.

89formula#1

Ok so i'm thinking of saving for the Probuilt full manual valvebody th350, hurst probuilt shifter, TCI 3300 stall converter, Spohn heavyduty driveshaft, and spohn crossmember. am I missing anything?? Sound like a good combo??

89formula#1

anybody??