my car doesn't serve as a long trip cruiser anymore (thanks to the wife and kid, and having the tahoe for them now) although it is my daily for now. but it does see track time often, and i'm just sick of dealing with my 6 speed...in sold on swapping to an auto, but everyone has different opinions on th350 and th400. i know each has benefits, and each has thier own quirks...

how many guys here have had experince with both of these in a fbody and what did you guys think? the guy thats going to building mine prefers the th350, but doesn't dislike the th400...i'm just not sure which one to go with...

 

for the record this will be rmvb and brake'd...

let the discussion begin

 

TH350 is lighter, and takes less power to spin, but its not as strong/durable. its got a lower 1st gear ratio, and try to find one with a lock up

th400 was actually designed for bbc with tons of torque for towing, they are heavier, stronger, last forever... in a stock vehicle,

hers the gear specs for both trannys
350 - 2.52 1.52 1.00
400 - 2.48 1.48 1.00

theres plenty of re-gearing kits available for both but id say save your money. if you get the th400 built properly they can actually gut some of it and save some weight while not losing any integrity in the strength area...

hope this helps

 

Depends on your power level. My TH-350 was ok until I went big cubes / big torque. Then it would blow almost every time I went to the track and it was built by a very good shop. It was at it's limit to what it was capable of. I had a TH-400 built and never looked back. 3 years now and more track passes than I can count and never skips a beat.

 

right now it's going in a bolt on car, but it's gonna see cam and spray soon. then, as soon as i can find a truck to take over daily responsabilities i'll put bigger n2o motor together for it (probably 700+rwhp). i just don't want to do one swap, then have to redo it again later when the bigger motor goes in.

 

If plans for more power in the future, TH400 seem to be the trans that could handle abuse at the track. I myself will be going to that swap very soon. Th400 rmvb w/brake coupled w/ a Strange 12 bolt rearend.

 

Get e 350 with an upgraded high clutch drum. This cost a little more but makes it alot stronger like a 400.

 

After reading about your long term goals there is not much of a choice. It really should be a TH400. It will live much, much longer than the TH350. Not much of a choice in my opinion.

The 350 is a medium duty unit. The 400 is a heavy duty unit.

g

 

+1, the 350 will never survive your planned 700hp...not ever. never. no chance in hell.

go with the 400 and save yourself lots of time and money (save money down the road that is )

 

What kind of power level are we atlking about, above 500 RWHP?

 

save your money and just do it right the first time! th400 looks like a clear answer. Not down talkin the th350 cuz I run one in my jeep that takes hard abuse, but Im only runnin about 300hp at the flywheel with a smb...more than that id change it out, especially with n2o. get a th400 and have it built up right from a good shop and you wont have to worry about it, and throw about a 3500 or 4000 stall in it for ***** and giggles!!!

 

I had a th400,rmvb,behind my 408,with a 4k stahl,and i loved it!I also run the same trans in the vette in my avatar,and it runs low 4s in the 1/8! So that ought to tell you something!But both are good transmissions tho!