The Money Pit

I've been through 3 TH350's so far,and the current one's still OK,but when it goes I thaught I'd switch to an overdrive unit. Has anybody done this?Is it holding up,or should I just go the TH400 route and don't worry about the mileage difference? I've seen a few transmission web sites and the torque ratings seem a little light for what I'm running.

WA 2 FST

There are plenty of Turbo Buicks running built-up 200R4 trannies that are over 500hp/tq...and before anyone says they don't make any bottom end TQ...think again. Spooling up the turbo on the line, they make plenty of low-end and mid-range TQ.

I know it sounds crazy that the 200-series trans could be built to handle this, but its done frequently. I think the key is that guys are not applying full power in OD, but using it only as a cruising gear.

If you don't mind swapping to a stick trans, the Tremec TKO and T56 will easily handle that.

Fevre

I have seen some heavy duty 200r4 onbowtieoverdrives website but it under construction right now so you might have to call them.

SuprJames

I am!! Course, haven't cranked my engine yet so can't give you much input. I know some guys around here that are running 400+ RWHP LS1's before nitrous with 4L60E's, which is why I decided to go with a 4L60 in my Vette. Got it out of a 90something truck and gave it to a transmission guy to beef up. I have the original 700R4 out of my Vette minus the tailshaft. It had a shift package of some kind and worked GREAT, but I've heard that the 700R4s aren't as beefy or flow as well as the 4L60's. Thought I'd rather be safe then have to redo it later.

GrandSportC3

Well - I'm not at 500 HP but I'm not too far :D :D . I use a overdrive tranny.. However - it's not a automatic...

:cheers:

Olivier

SmokedTires

Norval has some real world experience with this one :yesnod: .

I'm not 500hp yet, but I'm working on it ;) .

sventy2

I had a built 700r4 trans on the back of my 383 running a 175 shot of nitrious, car ran 11.3 at 120mph. never had a problem with the trans. wish I could say the same for the engine. Oh well new 427 big block making about 600 hp is going in this winter and I plan on using the transmission. It should still hold up.

SmokedTires

Welcome aboard sventy2, sonds like your goin to fit right in around here :D !

sventy2

Thanks, I love this site. Posted a few questions to the board already and I can't believe the responses you get. In a matter of a couple hours your question is answered, pictures posted, the whole nine yards!!!

gkull

Your TH350 can be built up and would be cheaper than a conversion. I just never had good luck either with my original th350. So when it filled the pan with busted chunks of metal the third time I opted for a hopped up late model 700R4

(sventy2) Could you tell us about your 427 (small block I assume)?

norvalwilhelm

I have quite a bit more power then 500hp but 2 summers ago I broke 3 well built 700R-R4's and 4 torque convertors in just 3 months. They were all built by the same person so maybe it was his problem and not the 700-R's. I was running slicks. The convertors all split the vains and they were all brazed.
I went with a Tremec TKO and street tires

Oldguard 7

you can build a beefy thm350 get some red devil clutches and strong torque converter. However I think a thm400 is the best.


[Modified by Oldguard 7, 7:50 AM 12/11/2002]

MARKUS_P

TH400 robs too much power, you´d be better of with a 450 HP engine with TH200-4R than 500 HP engine with TH400. just my 2 cents.
I´m planning to switch over to a TH200-4R after using myTH350 for some time. It was rebuilt and after my body off resto is finished I´ll enjoy driving the car for some time until I´ll take it apart again :crazy:

norvalwilhelm

A 400 looses about 35 horsepower more then a 350. A 350 can be built to handle the power and it frees up the extra 35 horse. I am a fan of overdrive transmissions with there low 1st gear and overdrive 4th.

Frank75

Why do the 400's suck up more power?

TedH

Your '80 really sounds like a wolf in sheep's clothing (406ci, AFR heads, Comp XE). Must be a joy to drive.

You may want to consider either the 4L60 (700R4) or the 4L80E overdrive transmission. the 4L80E is definitely up to the challenge but may pose fit problems in the trans tunnel. Bow-Tie Overdrives offers several levels of the 700R4 and are even starting to improve the internal hardware for increased horsepower levels. May be worth checking them out at http://www.700r4.com. Bow-Tie offers a Level II (450hp max) and Level III (600hp max) 700R4 kit that sound like they would suit your needs.

Tominator

On that show Trucks they mounted the new GM 572 to a th400 and a overdrive unit behind it. I can't remember the web site for that OD unit, geardrives something like that. The over drive unit can handle up to 1200 ponies. So if you add a nitrous kit down the road it wouldn't be a problem :D

But the neat thing is it electronicly controlled and makes your three speed a 6 speed. :eek:

The OD unit would probably require some fiberglass cutting to fit though.