vanillagorilla

iTrader: (1)

I'm thinking of swaping back to an automatic tranny to help compliment the turbo better than the 6spd, and I'm tired of being at the mercy of clutch manufacturers. Anyway, to give you a run down of things:

This is for a daily driven truck with some track use.
I plan on switching to a 3.08 rear gear and I run a 32" tire on the street, so overdrive isn't a concern.
I plan on having around 700rwtq/rwhp soon via a forged 370.
The truck weighs about 5000lbs.
I plan on using a 28" slick at the track.
I know I want a RMVB, but I'm still hung up on whether to get a transbrake.
I also plan on running a fairly tight TC of around 2500rpm stall.

Can a TH350 be built to suit my needs without costing more than an 80E? I know some will flame and say to just go with a TH400 or 80E, but the TH350 is more efficient, I like the gear ratios better, I won't have to modify my d-shaft and I already have two converter cores for one.

Can the Rossler TH350 handle it? What about TCI or ATI's competition versions? I see weight being the huge issue here and not the power/torque.

revtime

iTrader: (1)

I read all of your reasons for not wanting to go TH400 but it still does not add up. Your truck is 5000 lbs, weight is not an issue. 700 RWHP is more than even a built TH350 can handle reliably.
With that weight and horsepower the reliability of the TH400 setup will be well worth it in peace of mind alone.
I run a Rossler TH400 with a 4k stall behind a STOCK INTERNAL bolt on LT1, the gear ratio in the TH400 works fine.
Do you already have a bulletproof DS? If not your going to need one anyway so no issues with a custom length.
Just trying to get you into a reliable tranny, with that setup and a TH350 I would be worrying constantly about the trans blowing up.

Zombie

iTrader: (2)

A th350 in that setup is just silly and more expensive than a th400. The effeciency argument is pretty much crap unless you are running something like a stock eliminator class. I doubt there would be 1/10th of et difference between the two transmissions.

With that out of the way, I'm pretty sure that you can get a steeper 1st gear in the th400 to help you out with those big tires. I run a 2.75 gear and have a rossler th400 with a brake. There is no reason to go RMVB unless you are getting a trans brake. The other thing you might want to consider is having the trans setup so 2nd gear provides engine braking, I have mine done like this and really like driving it, no free wheeling in 2nd or 3rd, works great around town.

The trans brake is probably one of the most fun mods i've done to the car besides ditching the t56 for the th400.

PBA

The Th400 only eats up more HP in that if you accelerate extremely quick, the heavier gear train takes more HP to spin the geartrain. In a heavy vehicle that is not running extremely quick, the TH400 will have the advantage in terms of strength and reliability by far over the TH350.

vanillagorilla

iTrader: (1)

Well I just found out that a TH350 and TH400 converter is the same thing, so nothing to be gained there.

I'm not quite sure what you're saying revtime, but from my experience weight is an issue. For FI trucks a 60E is absalutley junk. Cars can have them live with around 700rwhp, but in a 5000lb truck the same tranny wouldn't last long with around 500rwhp. Weight is also why a clutch doesn't last long at my current power level.

So my next question is: would it more expenssive to have the driveshaft modified with a new yoke than it would be to beef up a TH350 up to the TH400's level. My driveshaft is a 2 piece and the carrier bearing is good at absorbing shock and hp, so it might only need the front portion modified.

What exactly is engine braking in 2nd gear mean? Is it like down shifting to slow down in a manual? I have a manual valve body TH350 in my 69' Camaro and when I let off in 2nd or 1st it feels just like it would with a manual tranny. Is that engine braking? How hard of a mod is that?

I decided a RMVB because it seems easier to drive on the street than a foward. From what I've seen though a t-brake is like only another $200 on top of it, so it might be a worth while.

Zombie

iTrader: (2)

I'm not a tranny guy so hopefully i'm not too far off in my explination.

In a forward manual valve body there is another band that is engaged when downshifting from 3-2 and 2-1. In a RMVB they remove this function and the transmission is then allowed to freewheel (feels like neutral) in 1st and 2nd gear. The problem with this is when you down shift or run the car out in 1st or 2nd gear without shifting to 3rd. Without going to 3rd the drum is allowed to freewheel and can reach an overspeed condition where the oil is slung off of it causing premature wear or even catastrophic failure.

In my trans the (I think it's called the 2nd gear intermediate band) is setup to work like a forward manual. With my gearing I cruise around town a lot in 2nd gear vs 3rd which was my main reasoning. I can also downshift into 2nd without as much worry of causing damage. I only downshift from 3rd to 2nd when I am on the throttle and accellerating though. I only downshift into 1st below 2500 rpms or if i'm accellerating.

Going to a RMVB setup without a brake is a sin. Once you experience a transbrake you'll want to use it all the time, especially on a turbo car. I leave the line at 10psi at the track and never have to worry about spinning the tires while building boost. Press button, spool turbo, let go of button, hold on tight.

You can probably have the yoke changed out on your DS vs having a new one made. I don't know about using a TB on a 2 piece DS though, might be a lot of shock for it.

revtime

iTrader: (1)

I only meant that with a 5000 lb vehicle trying to save 30 lbs by choosing a TH350 over a TH400 would not pay any divedends.
I too would wonder about a 2 piece driveshaft with a Tbrake........hell I wouldn,t chance it at all.

ls1408cp

iTrader: (37)

here is a good tranny for you https://ls1tech.com/forums/lsx-parts-sale/609007-th400-turbo-400-ultrabell-pics.html

vanillagorilla

iTrader: (1)

I'm going to go with a TH400 for sure. I've read up on the TH350, and it just won't cut it for me. I wouldn't be able to sleep at night. Besides it won't really give me any room to grow in the future.

I'm going to see if I can find a big 2WD diesel 1 pieces Al. driveshaft and have it modified. Are there different length tail shafts for the TH400? I think in my case, the longer the better, that way I could get a 1 piece driveshaft.

Gilbert@Ace Racing

We have a 400 in our 1st gen Camaro. It is behind a 427 that was dyno'd this summer for the 1st time. The trans has been living behind our 446 rwhp + 200 shot for over 2 years. It is a bullit proof transmission if it is built correctly. If you wanted to get out on the edge though a 700r4 is a viable option as well. They can take 700+ hp when built properly.
g

engineermike

I have a TH350 in my turbo Z28 and it's been flawless. The trans has been in the car for about 3 years now running anywhere from 550 to 700 rwhp and I beat on it weekly. I have had ZERO issues with it. Recently, I had it out to change the converter and I had the trans shop go through it just in case, and everything was perfect inside. I've been as quick as 9.9 at 146 mph, and have logged numerous passes at 140+ mph all at 3700 lb.

It's a plain-jane long-tail TH350 built by a local place (Action Transmission in Baker, LA) with a billet sprag assembly. $750 out the door!

Mike