Stolen Photo. This is what happens to a blue printed, faceplated TKX when fed big power (this was actually in a Cobra kit car -- clearly lighter than a Nova or Camaro). Work was done by Liberty. The case is too thin and there's not much anyone can do about it, at least within reasonable $$$. Now you know why Liberty was amused by my question of using one in “Jane”. :)

https://i.imgur.com/hcIhXwyh.jpg

They never, really, got rolling, as the owner took too long to build them 1 at a time. A friend of mine, with a '68 Chevelle 425 hp/383 got one several years ago and it had issues with clearance between 2 gears and kept taking out a roller bearing. I don't recall, exactly what the issue was, but he had it out and part 3 times and it took him many months to get parts for it and then he and another friend modified some of the pieces and tightened up end play and got it working good. For now. He knows if it breaks, there is no possibility of parts anymore and it will just be an expensive shelf ornament.
Last I heard about the owner, he wasn't going to sell the patents or designs for anyone else to build them and it is dead. Could be wrong about that and never say never, but it hasn't resurfaced in recent years. Jodie Haag doesn't have any mention of them on his website, nor does 5speed.com, other than attempting to get parts, maybe.

Many of these new manual transmissions have thin die-cast cases & tail housings. They try to rib them up but the strength is just not there compared to a thick-walled sand casting.

The better part of 800hp

Contact Jody Haag at Jody's Transmissions. He was building Super T 10s for drag racing. Maybe he can help.

I have been using a Clutch Tamer with the McLeod RXT clutch. The Clutch Tamer is probably why the M23 didn't break while racing.

BGH, Grant has been saying for years it's the clutch and it's engagement as usually why trans break. Big power, spinning at say 7000 RPMs, sticky track and slicks, Trans is fine driving around the pits. Now get to the line, dump it at that 7000 with a good still clutch, SOMETHING as to happen? Either car moves forward/UP, clutch clips, engine bogs or trans breaks?

Over clutch it with power can break the trans. This is partially why slipper clutches and CLUTCH TAMER were invented. How many years were Doug Nash 4+1 and Richmond 5 sps running with power and slicks? And I think the Nash were only rated at 450 lbs/ft of torque. BUT there you guys running them got years.

This is why I said to Napa, he's got some $$$ to do it right, so just go T56 and you get it rated @ 1000 lbs/ft and be done with it. Get some to "message" the tunnel to look OEM if needed.

When I had my 1988 5.0 convert GT Mustang, I went thru 11 T5's. NEVER at the track, always just on the street, usually playing a bit. Car was stock at the time, with 100 shot nitrous, long tube headers and McCreary "DIRT 60" tire. Ran 11.70's.

"BANGIN" Bob Hanlon from Hanlon Motorsports used to have a front plate conversion for the later Mustang 5 sp, I think they are 3650s, that you could put it behind a chevy and was good to about 500/550Hp. They were plentiful and cheap, so you could by 2 or 3 and swap them out WHEN they had issues.

With that much power, I'd go with a G Force 4 Speed. My buddy broke his M23 twice with a 700hp 496 and slicks and 4.56 gears, no clutch tamer.... My M23 has held up well at the track, but only has around 12 passes, I'm guessing my 496 has around 550hp. My M23 had to be repaired by Autogear twice under warranty because of quality control issues. If I was going to do this allover again, I probably would use something beefier.

Sounds like you cannot buy anything that is worth a chit anymore. Even when it's expensive

I agree with you. My M23 had issues with both 2nd and 3rd gear. The gears were not made correctly, they synchro rings didn't mesh with the gear properly. The ramp angle on the gear cone were not exactly parallel with the synchro ring which wouldn't allow it to shift into the next gear (2nd or 3rd) above 4,0000rpm... After replacing the gears, it's worked flawlessly. I had a close ratio Autogear M22 in the past which was the nicest shifting 4 speed I've ever felt but I never raced it with slicks.

This might be coming down to, "if it ain't broke, don't fix it" and just leave the TH400. OR, remove some of the bite from the beast so you aren't breaking manual transmissions ... :hmmm: