I am going to run a turbo 400 behind a Big block and was wondering if anyone has upgraded the sprag or drum to beef up the trans and if it is necessary? I should be running in the mid elevens if I am lucky but I dont want any failures. I will be running a 3500 stall and trans brake.

Super, any time I ask questions on this tranny I get very little feed back. Hopefully a Tranny shop will reply to your question. There's a couple guys out there from shops that have the answer.

I'm 30 pages into a book on the TH400...a good addition to a gearhead's library. "How to work with and modify the Turbo Hydra-Matic 400 Transmission...by Ron Sessions...MBI Publishing Company" I saw it sitting on the shelf at Barnes and Noble so I figured maybe I'd do some reading...

the only reason I ask is these are the only hard parts that jegs and summit sell for the turbo 400.does anybody know the weak links in a 400

Take a look at Transmission-Specialties They have plenty of T400's, parts and kits.

The 34-element sprag can be simply added in place of the existing sprag if you have the early drum with the smooth inner race. As long as you have it off, you can also use a Spiroloc instead of the snap ring to retain the sprag, which is a good idea with a brake. What kind of brake are you going to use? There are a couple I am happy with based on years of experience with them. One is the JW, and the other is the Hipster from ATD. Either are about $325, but I have made the move to selling the Hipster as I prefer the hydraulic circuitry a bit better than the JW. Pay close attention to instructions to install a TH-400 brake as you will drill a bleed hole in the direct drum after you take out the piston. Also use Teflon rings on the center support and pump. You can use a TH-350 Torrington drum bearing at the rear of a TH-400 to replace the OEM thrust setup. You may need to add a shim to limit endplay to where it needs to be with the bearing in there. If you have any questions feel free to email me about them.....or you can call me....it is a local call, lol....233-5677 is home. I probably do a good majority of the TH-400's being run by racers at CFR....Wepler, Praska, Holmes, Risse, Bjorheim, Kammeyer, Martin....... etc.