Okay, The TH350 in my 71 skylark went to the tranny graveyard. I have a mildly built 350 with 3.08 posi out back. Which is going to be better. I have a TH400 that I rebuilt on my own stock with a shift kit, I assume it works. Or my buddy is going to sell me a th350 he built that is strong and stout.So TH 400 or TH350. Which is better.
If you plan on running the small block, the t350 is fine. But for strenght the 400 is the best out there.
Yea, like Joe said. Turbo 400 should be tough and trouble free for you. For a mild build the turbo 350 should be fine too. I think the turbo 350 also has a lower first gear, which might make your car perform better. I used to drag race a BBC camaro with a turbo 350, and never broke it.
Thanks Devon! In real world terms, how much do the difference in ratios affect performance. Would i really notice the difference? Someone help me with driveshaft length differences
I doubt you'd ever be able to tell the difference between four hundredths in terms of ratio. If you use the search feature with the words th350 th400 driveshaft, you'll get some good reading. Devon
The gear ratio in the 350 alone probably wouldn't make much difference. The combination of gear ratio, weight, the fact that it uses a little less horse power to turn might be noticable.o No: Bob H.
got the numbers I needed, Thanks guys. Are you saying it will take more hp to turn the TH400 with my 350 than the TH350? Has to be marginal right?
Again, you're right...marginal. The guys who are trying to eek out the last few hundredths of a second are going to spend some money to beef up a TH350 because of not just the lighter overall weight, plus lighter weight of the reciprocating parts. The aftermarket offers lighter stuff yet, for both trannys. I wouldn't make weight a serious consideration unless I was going racing big time. The weight difference is about 20 lbs wet if I recall? Maybe somebody remembers weighing the two. Devon
Yeah, I would agree with you Devon. The only racing this cr sees is the occasions tire spin at the light to put an ear to ear smile on my 4 year old! A young Buick lover in the making! Thanks guys, have a wonderful holiday
If car has 350 trans, you'd need to change unput yoke on driveshaft also, and get the kickdown switch and wiring required for the 400. Easier to stick with the 350 trans, as that is what it is already set up for.
I was told by several gurus over the years it takes 22hp to run a turbo 350 and 44 hp to run a 400 trans so you decide. behind a small block you would never need more that the 350 if its built right.
As Jakeshoe has pointed out several times (probably to the point of exhaustion), the weight difference between the TH400 and TH350 reciprocating parts is negligible. And transmissions do not "consume" horsepower. Since you have a 350, a TH350 will probably be sufficient and serve a long, tough life. A TH400 would also work fine, but you'd have to change your driveshaft & yoke, probably move your crossmember, maybe change the speedometer gear in the TH400, and some other stuff. Personally, I'd leave well enough alone. Don't forget to check that your other TH350 is also a BOP bellhousing, not out of a Chevy. -Bob C.
Since most of the forums have mentioned the 200 4r overdrive transmission and that it should be little effort to retrofit into your Buick, perhaps you should be thinking that way. Heard it can be built to withstand big hp. They also have a uni bell, that will fit bop or chevy pattern. :rant:
+1, My GN will run all day at 70mph at 2000 rpm. That is with 3.42 rear. With a shift kit and a few hard parts it will easily handle a 350.:TU:
Bob, all transmissions consume HP, none of them are 100% efficient. That is one of the main reasons that rear wheel HP is lower than flywheel HP, the other power robber being the rear axle gears. I have also heard that TH400's consume 22hp more than TH350's so, unless you need the added "beef" stick with the TH350 or go with a 200r4 IMHO. Does the TH400 fit in the trans tunnel?
