[chuckies76ta]

Ok, Well that changes it from what I'm using. I don't have a trans brake on mine. Still Hughes does make one with a Trans brake. Be nice to find out what you have so you can make sure of the mods that are needed in the transmission when this valve body get installed. Maybe previous builder has done them. Is there a drilled bleed hole about .060 in the direct drum? Oh, and some of these valve bodies do not use gaskets.

[Half-Inch Stud]

No VB nor Case gaskets means pressure leaks, yet slow leaks at that.
Center support bushing at 0.004" is close, in texting, but worn in real life. $10 bushing, go fir it.

[73LeMans]

Just an update....a very long road to get here, with plenty preventing this from being a priority, but to think positively, this TH400 is back together, done by me, (1st time!) and ready to go in the car. Whether ot not it runs, remains to be seen.

Here is what went in -

• ATI Aluminum FWD / Steel Insert Drum w/300M input shaft
• ATI Billet aluminum pro mod 36 element sprag direct drum with billet aluminum piston
• ATI center support with billet aluminum piston
• Raybestos Stage 1s
• New pressure plates and steels
• ATI Low Roller Clutch
• ATI Stock Transmission Overhaul Kit for all gaskets, seals etc
• FTI Performance Transmission Case Saver
• TCI Transmission Bushing Kit

I bought a Sonnax Clutch Hub when I thought my existing hub needed replacement. Local builders agreed I was mistaken and said its fine. It was still concentric and its a billet unit, just not as light as the Sonnax. Rumor has it Sonnax unit causes some clearance issues anyway, so was happy to put back in what worked previously.

Here is what I learned

1.) Order parts early - the direct drum from ATI was a 3 week wait - which isn't terrible compared to some other wait times.


This unit is beefy compared to the previous 34 Element -


2.) I didn't know anything about the Exedy frictions ATI sent with the kit.....so I bought a Raybestos friction module for peace of mind instead. Anyone race Exedys successfully? If so I'll hang on to the plates.

3.) Clutch clearance matters. Or does it? Clutch material matters. Or does it? So many opinions. From what I read and watched online, compared to what experienced builders local to me say, it seems there are two schools of thoughts here...but.most converge near the .010" per clutch, and Raybestos, so thats what I went with.

4.) Proper J tools are in my future. Not that they make one to load the direct drum though. My finger tips from taking that loaded unit in and out 2 dozen times still hurt a day later. At the very least, getting the tool to install the lip seals would be nice...although the plastic laminate sheet trick works well!

In an effort to for anyone to learn from this post, let me throw in the one piece of advice that made a big difference. Once clearances have been determined in the direct assembly, unload it and only load it in the case, after its gone in for the last time. Due to its weight (even the aluminum one) its difficult to manipulate. I could never get it to seat through that last intermediate clutch. Thought it was down all the way many times. Wasn't down all the way. Caused the pump to sit too high. That was fun to figure out. (Read - "infuriating waste of time")



To answer Chuckies76ts's question from so long ago (apologies !) I did discover the previous builder did all the typical stuff done to it - 4l80 drum, dual fed direct, valvebody mod etc. The charge pressure mod wasn't done, but as noted, I took care of that. My only complaint.....well not really the only one.....is whoever put it together last, (probably the builders shop monkey) I surmise used the bolts to draw in the reverse servo cover and the front pump. I had stripped threads in one of the cover bolts and two pump bolts lost their ability to hold 18 ft/lbs.





...so make sure you have a lot of these hanging around.



Not a challenging job, but not fun when against a deadline. Finding the proper helicoil can also be challenging if you trust local Autozones Oreillys or even NAPAs to have them. Thank goodness for Grainger. 45 min away, but worth the trip.

This pic below, minus my finger is just cool, so Im posting it. Along with the pretty FWD drum.





Didn't change all the bushings...seems odd to have something rebuilt and not do everything 100%, but I did change the pump bushing, the reaction carrier bushing, and the extension housing bushing. New center support bushing came in the new unit, so it saved me some time there. I did not do the case bushing...fingers crossed on that one. Which now reminds me.... need to buy a decent seal installer kit. Had to borrow a friends...twice! I need a press too. And some J tools....

The REAL point of posting is to thank everyone for their help. Between folks here, Hutch and others in the DIY TH400 for Drag Racing FB group, Shawn Mountain and Southpaw Autoworks on YT, not only do I have confidence in this build, but I might even do another! That is, f it runs.......

[Jack Ferris]

Originally Posted by Ken MacNicol

I have been doing burnouts through all 3 gears for over 30 years, and have never broke a sprag in a th400.

Same. In fact, I have the same sprag I bought from GER (leader in junk trans upgrades) back in 1990 and while I've busted up other things, that same sprag is still in use.

[Johnny406]

Here's the planetary I blew up a few years ago in my TH400. It was a weaker lower gear out of a 200r4 I believe...

[Tim Corcoran]

I did the same thing with my TH-400 last year at Norwalk, took out 2nd gear it was like 2nd was neutral 1st and 3rd were fine. I haven't done anything with the trans since I had a spare. This is a great thread, even if I am not willing to take on the rebuild myself at least I can take some notes and have a discussion with whoever rebuilds it for me.