I am looking into switching from my M6 to an automatic. I read the sticky above but still looking for more info. Can someone give me the pros/cons of both the 350 and 400 tranny? I have the option to buy both, and also have the option to by rebuilt stock ones with upgraded parts. I am looking for any help I can get. I have no idea what I need in an automatic transmission, but it is mostly a strip car. I also would like to have a transmission I can grow into as well, so it will have to be capable to hold some high HP in the future.

Thanks in advance.
Kevin

 

This is kind of what I understand between the differences. The 350: lighter, lower first gear. The 400: can handle more power, cheaper to build. If it's just a strip car and gonna have some high hp numbers in the future then I'd just build a 400 and not have to worry about it. I know that some are gonna say that their 350's can handle anything you throw at them but I'd still get the 400 just to be safe. I too am looking at building me one of the two.

 

since were on the topic, does anyone what the difference in power loss would be between a th350 and a th400, assuming they were built the same, same t/c... etc

 

pretty sure most tranny guys you talk to will tell you a th350 can handle "most" SBC's...

i sent mine to ATI and had it built for 1000hp..

but a lighter car will make it easier on any tranny

the bad thing about th350 or 400's is no over drive so if you want a higher gear 3.55 for the street a th350 would be more your game because of the lower 1st gear to help you launch....

but im biased because i have a th350 and love it even with 4.10s

mine will be getting a raping this season with my new setup and im not afraid to stand on it...

 

I went TH350 and have brutalized it, totally happy with it. 400's will take more power no doubt about it. But, to me the TH350 more efficient, weighs less and handles the ~430rwhp NA + 250+ shot of juice off a transbrake launch, so no worries yet.

 

a 350 has a 2.52 first a 400 has a 2.48 first so the difference in low gear is about 3.5% you wont notice that. The difference in hp loss from what i heard is around 7 hp but i know that many many companies offer aluminum drums and low drag components. As far as which to choose it depends primarily on the dependability and how crazy your going as far as power.

 

Here is something I just found on this subject:

http://h-body.org/library/hbodyfaq/hbodyfaq-10.html

You really don't lose that much horsepower between a TH350 and TH400. I've heard as little as 6 hp. Hardly worth worrying about...

 

like everyone else said
TH400
cheaper to build
can handle more power
eats up more power
heavier

About the low first gear you can get both the th400 or th350 with a 2.75 first gear. My tranny guy can get you a 3.05 first gear in a th350 not sure if he can put it in a th400 though.
I'm all bout lightweight so i got the th350.

 

that 1st gear set adds a HUGE difference to the price.

if you have under 600hp the th350 will be the better choice.
lighter, faster, easier fitment. no new driveshaft yoke to buy, etc....
1st gear is irrelevant between the two.
the th400 comes in handy on heavy nitrous or boost.

th350 vote here.

 

Thanks for the info. guys..

What does everyone think about the tranny brake? It is not a daily driver, but how much of a pain is it to shift manually on the street?

I am also going to be swapping from a M6 to the automatic. Do I need to get a new radiator, or can I just run a tranny cooler and be done with it?

What is the weight difference between the two transmissions?

 

TH350 here, no trans brake, i run a line lock, i am also running 4.10's and love them. At the time, i had a chance to get a really good deal on the TH350 and went in that direction. I know my tranny builder pretty well, i recently found out that the price of rebuilding a TH350 is only around 180.00 (without labor) thats blew me away. Either way you will be happy.. When i lost my 4l60e, i didnt loose any sleep..

 

I went th400, somply because I know that I'll never break it. I'm going to be launching off the transbrake, and knwo that eventually I will be making big power, so it seemed like the right choice. My car's heavy too... so that's some added stress to the tranny as well. Realisticially, I never see my car getting under 3400 with my 275 lb *** in the car, that along with the enventual power of a big CI motor, I figured it would probably be the better way to go. I'm on a 4.10 rear as well for now, but may swap it to a 3.73 if I find it's spinnign too many rpm at the end of the 1/4 I went with a big converter, but it's very effecient, so it may still be o.k.

 

trans brake is going to require a reverse pattern valve body, as too a shifter than will work with a reverse setup.
if you arent a bracket racer, or an all out ET getter, id go with a good ole foot brake.

dont need a rad, just get a good cooler.
the weight is prolly 30pounds if i had to guess. ive lugged a few and its quite a difference.

 

Tranny I have has a RMVB in it too. Just ordered a hurst quarter stick from summit, made sure it was the one for the reverse pattern, so I'm all set there. The only races that we generally have in the area that I can go compete in are bracket races. Seeing how there's no ls1tech series, or even the EFI series this year to go to, I guess the only racing that I'll be doing is a couple good sized bracket events at one of the local tracks. Besides, I'm not sure that the EFI or tech series last year even had much of a class for a low 11 second car, which is where I figure I should be this year.

 

I'd get the Trans Brake, I do have one now, and I love it. Mine is a Daily Driver, and shifting manually is nothing special, sometimes interesting, never complicated.
You can use the stock radiator, just get a nice cooler up front, most bypass the cooler lines in the radiator once they go big stall anyway.

 

I might not have read that right but your saying, to have a trans break you need a new shifter for the reverse valve body, can you explain on that for me? I want a th400 with a good 3400+ nitrous stall with 4:10s and a trans break but would i need a stall if i had the trans break?

 

if you plan to drive it on the road like i do mine.... 4.10s, Th350, T-brake and 4k stall with street tires then plan on taching 3200 rpms at 60 mph....
in reality after you get some horse power a 3.55 or a 3.73 will be enough to pull you out of the hole with the th350's low first gear.


and yes even though you have a Tbrake you still need a stall...


Ps: i will be switching my gears to 3.55's

 

The 4.10's and my th400, should work for me on the street.. I think the 3200 on the street is still o.k., and I figure with the 28 inch height e.t. radils I am gonna run this year, the rpm will probably be less then 3200. But then again, I won't know that for sure, as I think my speedo needle will be sitting at 0 from now on.

 

I was trying to figure out what size stall to use for a th400 that can with stand a 200 shot, so what do yall think? Ill have the 4:10s in the rear and have slicks and skinnies so im not worried about traction.

 

call ATI