bluegtp

my th350 took a crap on me a few weeks ago and I'm having to rebuild. A bud has a th400 that he said I could rebuild and have, so which would be the better route to take?

Gas mileage is killer with my 383 and the th350 with the 3.55 gears....would the 400 be much better, would there be a performance loss much?

what would I need to make the 400 fit? vette tailshaft/yoke?


thanks for any advice/comments....I don't have the extra cash to do a 700r4 conversion w/ having to buy a new stall convertor,crossmemeber, yada yada yada....


ryan

FRSTR90

If I am correct, the most a Th 350 can handle stock is around 400 - 450 hp... The Th 400, however, can tolerate 700 hp stock. I am going to assume that the th400 will take more hp to drive. I doubt the difference in mileage is even noticeable. For many people now a days, I think people would complain that the Th400 is rather harsh when you put a car in drive or reverse. Personally, I love the stock Th400, it think it was a shame they did away with it. I guess when GM started robbing the engines of HP there was no need for such a Heavy Duty tranny and replaced it with the th350.

gator79

go with the 400 or if you are not making crazy hp go with an overdrive trans

ajrothm

Keep your TH350.. No point in changing to a 400 unless you are gonna seriously build up your engine. TH400 has more parasitic loss, requires different yoke, different kickdown device(cable) and you would probably have to mod your crossmember as the 400 is bigger I believe.

It will definetly suck more mileage away.

If your th350 is toast, just rebuild it, even a basic rebuild on a stock TH350 will hold 450hp. I ran high 11s with a TH350 for years on a $150 bench job rebuild.

GrandSportC3

Slightly build up the TH350 on the rebuild.. With just a few better parts on the rebuild, the TH350 will hold up to 450 - 500+ HP..

The TH400 is heavier, has more parasitic loss and will result in slightly worse gas mileage..

The best solution would be a Grand National TH200R4 as it has a overdrive and your gas mileage will greatly improve. It's also a bolt on..

Glassbowtie77

That's the way I'm going when the time comes. I might even throw my 3.08's back in if the price of gas gets high enough, I'm not looking to race anybody, I just want to be able to afford to drive my car more often.

fauxrs2

gyopp

I had a local shop build mine that has built several TH350's that see the drag strip every weekend. The fellow there told me that he had a couple of guys running them at approx 700 HP with no problems, not stock tranny's of course. He built mine for $800 wit shift kit, heavy drum & sprague, and other goodies. Reflecting back, even thought the 350 is good tranny, I wish that I had spent that money toward the 2004R.

BlkBird

Keep the TH350.

bluegtp

looks like i'll b keeping the 350 then....thanks for the input guys, very helpful......

what's a good rebuild kit to go with out of jegs, summitt, or whatever?



i'll be pulling it apart tonight probably to see what went wrong with it.



ryan

comp

what was your MPG ?

bluegtp

ha, that's a good one....i really have no clue.....I just got the speedometer working when it decided to go....


Part of the problem is my foot's always in the throttle....it maybe gets 12mpg....on a good day without running it hard and on the interstate....i don't drive it often, maybe once a week to work or out on the weekends....