Bulletproof TH350 ?

[oldskool]

I read that the A-1 Proflight 350-Strip Super Stock is one of the strongest TH-350 trannies made. But they are $6000.

So my question is, are there any of you guys who build TH350's that will live behind a long stroke engine with just over 700hp and about the same torque ?

Are some of the 9 sec SS guys using a TH350 ?

If you are one of these guys would you please post your info about the trans and who built it. Please include links to the builder, or contact info if available. Thanks !

[old tech guy]

The A pro flight is a Chrysler torque flute developed by Dave Smith good for 1400 hp

[Bob Mulry]

The question should be what's fast and not what's strong........

You could almost get away with an AAMCO rebuilt TH-350 trans for 700HP if all you want is strong........

Bob

[oldskool]

Originally Posted by Bob Mulry

You could almost get away with an AAMCO rebuilt TH-350 trans for 700HP if all you want is strong........

Bob

I'll just assume that your statement is just an exaggeration. When I got my 1st 455 Pontiac engine I was not aware that 500ft lbs of torque would tear up a bunch of stuff.

A local racer had an 11 sec sbc Nova, with a TH350. He decided to switch to a Glide. So I bought his TH350. The TH350 had worked just fine behind his sbc. But that was because it had very little low end torque. But my 455 had about 500ft lbs @ 3000-3500rpm.

So, on the first 1-2 shift, it broke the int sprag race. So, I checked around and was told that big blocks needed a hardened sprag race. So, I bought one from TCI. I figured that would fix the problem. But apparently the hardened race was just more brittle. It broke into several pieces on the first 1-2 shift.

So, I had a another stock race put in it and sold it to another sbc racer. So to say a stock rebuilt TH350 will hold up behind a race engine with 700ft lbs of torque is ridiculous. If you can do it, fine. But 99 & 9/10 % of other racers can not get by with a stock rebuilt TH350.

There are several tranny guys who advertise TH350's good to 800hp or a little over. But I decided to ask some of you class racers about it. I assume that some of you guys with big block engines are making over 500ft lbs of torque and are using a TH350 to run a little quicker than with a TH400.

http://www.atiracing.com/products/trans/350/

http://www.atfspeed.com/store/index....x&cPath=193_53

http://www.coanracing.com/Catalog.as...uctDetail=1585

http://www.jakesperformance.com/TH350.html

On another site someone ask what tranny would hold up behind his 700hp long stroke Pontiac engine that will also have around 700ft lbs of torque. When I mentioned a TH350, several guys jumped on it saying "no way". Since I'd read on this site about you guys using TH200's and TH350's, I decided to ask about it.

The common upgrade I read about online is a 36 element sprag and drum assembly. Some even advertise a spagless set-up. So I just assumed that you guys would know who builds these HD TH350 for most of the SS racers that will survive high torque race conditions.

http://www.summitracing.com/parts/tci-327900/overview/

http://www.ckperformance.com/List/GM...missions/TH350

[Mike Pearson]

If you are bracket racing with the combo that you have listed in the previous posts you would be better off with a powerglide. The A-1 trans is referred to as a Protrans. These are typically light weight rotating assemblies for stock, Super stock and comp type racing. They are designed for max performance and not so much for max strength. Coan also makes a similar light weight turbo 350 its called the XLT. The cost is similar. I would talk to ATI,Coan or Rossler for a recommendation on the trans for your combo

[Jim Kaekel]

The 36-element upgrade for the intermediate sprag is the cure. Not a cheap upgrade, but it will prevent failure.

[Jim Hanig]

If its a bracket car put a 400 in and be done.

[Bob Mulry]

Originally Posted by Bob Mulry

The question should be what's fast and not what's strong........

You could almost get away with an AAMCO rebuilt TH-350 trans for 700HP if all you want is strong........

Bob

All a TH-350 needs is cut down Intermediate Piston to take 3 frictions, a 700R4 Lo Roller, a hardened or 36 element sprag and a shift kit................

and I did say almost.........

AND LAST BUT NOT LEAST

Start your burn out in 2nd or high gear to reduce the shock loading on the intermediate sprag

Bob

[Mark Yacavone]

400's break intermediate sprags too.

[oldskool]

Originally Posted by Mark Yacavone

400's break intermediate sprags too.

Yeah, my 1st 455 proved that to me. After it broke the 1st one, I ask around and somebody told me to ask a local tranny guy who had built lots of TH400's for the local racers. When I described to him what had happened, he said, yeah, it broke the int sprag.

Well hey, I was just starting out. I'd never even heard of an int sprag. He said all I needed was a GM sprag for a TH400 that came behind a 500 Caddy engine. So he put one in for me and I never had any more trouble out of that tranny.

Then I bought a TCI "Full Competition" TH400 with a reverse pattern VB, for another car. But my 455 broke it too. When it broke, the guy who was driving the car came back from a time trial and said he didn't have any 2nd gear. So I told him to just hit the ratchet shifter twice real quick and see if it would shift from 1st to 3rd.

He did and it did. It only ran a couple of tenths slower. It was a bracket race. So we just dialed in to the slower time and he won the race.

I ask the tranny guy about it and he said that just because TCI called it "full competition" did not mean they had put the HD sprag in it. He was right. He put one in it and I never had any more trouble with it.

I suspect that TCI changed their tactics a bit since those days. Anyhow, I think several of the tranny shops use to buy the Caddy sprags and repackage 'em. In recent years, they are probably made in China. I see the 34 element sprags on Ebay for anywhere from about $50 to almost $100.

http://www.ebay.com/sch/i.html?_odkw...&_sacat=171114