I have put about 20,000 miles on a Turbo 350 I rebuilt a few years ago with a B&M trans kit. I just left all the stock parts in it. I would like to refreshen it, and build it so it can handle 500hp. Besides the sprag, what else do I need to upgrade? Thanks, Scott

The sprag is the main thing, along with a deep pan and an external cooler, my original th350 was a stock rebuild with a BM shift kit and it lasted for 4.5 years and was working great when I swapped to the 400. The guy across the street went thru the 350 for the guy I sold it to and he said it looked great inside,just slight burning on high gear clutches, stock sprag even looked fine. 2 full years of racing, running many low 12 high 11 second passes @ 3900 lbs.

I've got an external cooler, but I will need to get a deep pan. I think my trani. is beginning to slip becuase sometimes when shifting into high gear it doesn't break the tires loose anymore. That is why I wan't to put new clutches in. Also, I remember there was some machining I could have done that would allow me to stick another clutch or two in, and I might do that this time.

I've got 4 years on my TH350 and have slowly stepped the engine up to right about the power level you are looking at. No problems -- even with the stock sprag. I did have the pistons machined to make space for an extra set of clutches and installed a B&M shift kit, but other than that it is stock.

I think the clearance in the clutch packs is important too -- maybe some of the real tranny gurus can explain better than I can, but IMO if the clutch packs are real tight they hit harder and stress the sprag more. Its been a couple years since I've been into my trans but as I recall I set the clearance up at the loose end of what is considered acceptable.

The other important thing (besides cooling) with the TH350 is that you replace all the bushings in it. The tH350 is known to be a little weak on support -- there's not much holding the middle of the rotating parts mass so when bushings get worn the "guts" tend to wobble and stress parts.

That may be a little over-simplified, but I'm no pro tranny builder . . . just a DIY cheapskate LOL

PS. forgot to mention a good oil pump is important too . . .

I will find out tomorrow if they can handle 600+ hp, not sure how many passes I'll get without a rollbar though, I have the SW rollbar kit, but need/want to make at least 2-3 passes to see what she'll do before I put her in the shop for the rollbar installation. The th350 is all new inside, so it might last a little while.

can't wait to hear robert.

The Th350 can handle right at about 600 lb/ft without frequent failures with minimal mods.

That is about the limit IMO.

After that stuff starts to break. Inmput shafts, direct bushing, etc..