I am dropping off my th350 in the am for a rebuild. The performance rebuild includes hi-performance clutches, drums machined for extra clutches, and their in-house stage 2 shift kit. They advised they prefer their own tranny mods and shift kits because they have had so many problems in the past with kits like B&M, etc. Anyway, the guy advised that my application will be pushing the limits of using a hardened intermediate sprag race, saying they have a tendency to shatter under high torque applications because they are more brittle than the good factory "250" sprag races. They also stock the "250" units. Any thoughts?

I think a hardened sprag is what, $50.00....get it.

The money isn't the issue...I had full intentions of getting the hardened sprag race installed like I did on my truck tranny when they built it. But, the builder had mentioned that the hardened races have a tendency to shatter under high torque loads. I thought the hardened race was to keep them from shattering???

Haven't heard that before. Sounds theoretically possible. Maybe someone from the tranny forum will check in and give some tips. Maybe the moderator can move this thread there.

-dnult

I just have a factory HD one in mine (maybe a "250" ? don't really know). I've broke all kinds of stuff in my TH350 but never the sprag race. First time I've ever heard about a hardened race shattering.

When I was running a TH350, I broke the sprag 5 times in two years. Three of them were hardened. I did all brands, TCI, ATI, & TSI.

The OE units lasted the longest. I did have a B&M Shift Kit, Stage 2, and it did hit 2nd gear hard, teeth-shattering. This trans was in a '68 weighing 3000#. Now I have a P/G and run 11.90.

I have one, as well as many others around here, and have only seen one break... :confused:

Don't waste your money on the hardened race. They break just as easily with the stock sprag, cause it is the sprag that fails and takes out the race. I just replaced my sprag and race last week, again.

It is not the sprag elements that fail, it is the race. Most often they split near the drilled lube holes in them. The aftermarket ones are actually better, but most often it is a shift timing issue that kills them. If you want it to live, look to the better drum/sprag along with the race. If you need info/pricing on parts, I will likely save you a bunch of money on anything you'd need, and would be happy to work with your local builder to get parts for him. Just email if you want to.

I'll accept the shift timing issue being a problem, and I am no means a tranny expert. I've built three TH350's for me, three different cars, and one for a friend and a few race only transbrake powerglides. This is the only TH350 I put in a stiffer pressure relief spring into and it is the only one that I have broken two sprag assemblies. One was stock and one was the hardened unit. Each lasted about the same amount of time. I put in the stock pressure spring this last time and it does shift different.

If the sprag element doesn't fail, why do major trans companys sell an upgraded drum/sprag assy? If it is purely the race that fails, it would make no difference what sprag was in it, so I would think buying the upgrade would be a waste of money. My sprag was spread apart and the springs were crushed. Again, I'm not an expert, but it just seems logical to me that the sprag failed first.

Steve, in your post you said "It is not the sprag elements that fail..." but then try to sell us a better one. :confused:

Lonnie

Got the tranny back today...heres what I ended up with. Hardened sprag and race, trans-go stage 2 shift kit, extra clutches (some kind of kevlar clutches), raised shift point, a heavy duty aftermarket 700r4 roller clutch (?), and other misc. mods. That trans-go kit looks pretty sweet...it even comes with springs to modify the shift points (5 different settings). The tranny guy was really cool...very much a gearhead. He is one of those kind of guys thats gets all giddy talking about high performance tranny building...definately loves his job. I cannot wait to get this thing out on the street :D

You only need the beefy one if you are making some power, that was what I was trying to get at. The reason for the 36-elements is to spread the load out better on the race more than anything. But yes, it will reduce the per-unit load on the sprag elements too, which is a necessity with more torque being applied. Most of the time, guys run no wave plate in the intermediate clutches thinking this will make for a better 1-2 shift, or a high-pressure-producing manual valve body, or a poor shift kit, and then wonder why the race split on the 1-2 shift. Hope this clarifies what I was trying to say! :D