8550ta

I kind of mentioned this in another post, but I figured that I would get a better response just posting up a new topic. My th350 is on its last leg, so I need to decide what to do next. My two options are spend slot of money on a th350 and hopefully make it strong enough to last the abuse. Or I can switch to a th400. I think that I am leaning toward the th400 , but I am slightly concerned with it robbing hp and taking too much time from my ET.

So let me know your thoughts and experience with this situation.

DIGGLER

iTrader: (1)

the difference will probably be small enough to where you wont notice... i would go ahead and do the th400.

we are fighting a th350 in a friends car right now. was rebuilt with a decent converter, and after 300 street miles and 15 passes on the bottle the bottom of the pan already has a layer of clutch material in it.
60' and et are decent off the trailer, but passes after that it gets worse. also its down 3mph or so. i would almost say torque converter is damaged, but the clutch material in the pan has me thinking its the trans.
his car @3100lbs and 508rwhp has a best 60' of 1.45 so far.
back when my car made 470rwhp @3050 had a best 60' of 1.34. both cars leaving off the foot brake, on the bottle, same overall suspension/tires etc. my car had a th400 though.

ZONES89RS

iTrader: (2)

I have seen the TH350 last in a BBC with nitrous on top of 15 to 1 compression and all the works. But yea, he has money in it, so for the dollr sake, go TH400 so you can not worry about spending a ton of cash. But then again, i have scored some killer TH350s used that were beasts.

mw66nova

iTrader: (13)

th400. it's not even a question. i've had both, i like my th400 better. (granted, the th350 was behind a completely different engine).

so far i've put about 300 street miles, and have about 6 passes on it, so things are going to get better even still. the trans has a deep aluminum pan with cooling fins, and has a plate style b&m super cooler (only b&m product i'll ever endorse, lol). the converter is a Transmissions Specialties 9" unit, 4500 stall speed. transmission temps never over 160, even after a 40min cruise at 50mph.

8550ta

What do you have done to the inside of your th400?

mw66nova

iTrader: (13)

bte pro brake valve body(reverse manual pattern), it's got rollerized bearings, case saver, and some other basic odds and ends. Shagwell built my trans so he could tell you more about it.

Fast 383

iTrader: (2)

Do yourself a favor and make the leap now.
Will it rob a bit of power? Probably a tad.
Will it be a pain to change you crossmember and driveshaft, yes!
But it will be worth it. YES!

A Turbo 400 was a brute trans from the factory designed for heavy and powerful vehicles used to move weight. It's perfect for racing applications. With the minumum in parts (34 element sprag) they can handle 850 HP reliably. I have seen them go 8.50 - 90's consistantly.

the problem with the T-350's is that even after you throw the highest dollar parts at it you can not over come the factory weak links. The cases are weak. They blow bellhousings apart and split cases. The valve body portion at the bottom of the case is usually not flat. So if you put on an aftermarket valve body it will rock on the case instead of sitting flush. I have heard of some people milling the case but thats a real hassle if you ask me. The stock size sprag and race for the T-350 are junk. We use the heat treated race and I have seen it break behind a 400HP crate motor in a 2700lbs nova.
There is a good upgraded 34 element drum and sprag but I have also seen that break behind 600HP 406 in an S-10. Pretty unpredictable if you ask me.

Some people go 400 passes with a T-350 and some people go 4. I guess you just have to wonder which one of those guys are you?

IMO, and I sell these every single day of the week, the 400 in it's OEM form is as strong as a T-350 that is built to the gills. The ironic part is that the T-400 is cheaper by a few bucks.

8550ta

Oh I am definitely the guy who will make 4 passes not 400. Thats why the last time at the track I only made 2, so I should have about 2 left in her

I am almost certain that I will go with a th400 now. The trans is one of the last things to go through since I started attempting to bullet proof the car. About how much does a car typically loose going to a 400

mw66nova

iTrader: (13)

i think what everyone is saying is that the loss is negligable...maybe not unmeasureable, but the difference is so small that weather conditions will play a larger roll.

Fast 383

iTrader: (2)

It's adding to the total overall weight of the vehicle and the amount of rotating weight bolted to the crank. So you may not see huge differnces from a direct swap but in the long run when you add a good rear to the equation there will be some drivetrain loss.

I ran with a 383, T-350 and 7.5 rear.

Now i'm running a 6cyl Turbo, 200R4 and a 9 inch Moser rear that weighs 4000 lbs.

I can assume that i'm gonna slow down from the trans/rear but thats the breaks. Need to have the stuff built to get the car down the track.

When I get tired of this combo, i'm gonna build a FI BBC turbo and a T-400 is the only choice.

mw66nova

iTrader: (13)

i feel ya on the 9". if i didn't already have it, i'd be looking at doing an 8.5" 10 bolt build, just because it's so much more efficient, and can handle what i'm trying to do right now.

greezemonkey

iTrader: (14)

I gotta fly the TH 350 flag, after several years and only 1 case and a set of planteries. it has several hundred passes from a 496 making no less than 800 at the flexplate and getting hit with minimum of a 150 shot and the last two years, two stages currently at 400 HP worth. This past weekend it just went 1.30, 5.46 / 131mph to the 1/8 and 8.58 / 163 to the quarter. Thats at a 3483# race weight. just saying they can be done to hold up, its had the same clutches for the last 5 years also. Guy that built it and the converter is a member here if you need verification.

Fast 383

iTrader: (2)

mw66nova

iTrader: (13)

i'd have to say that scott and rich (car_fixer) are the exceptions to the rule.

Bullydawg

iTrader: (7)

What TH400s are the good ones to get? I'm most likely headed that was after my new engine.