As someone keenly interested in this topic and home-brewing strengthening options, Ive been searching fruitlessly for pics of internals from failed 5sp boxes. Would love to see some.

I'll see what I can do, and link back here if i can put something together

No, I have never broken 4th in any of my 5 speeds. I have not broken any at the track yet either, always on the street, in 2nd, 3rd and 5th.

Here is my most recent carnage, I didn't open this one but this is definitely an input shaft tooth, matched it to a different one. I did manage to keep the input shaft from moving forward and sheered the whole tooth(I think), I had only sheered approximately 90% of the teeth previously.

I will email them today, I have an unusually busy day though.

https://cimg5.ibsrv.net/gimg/www.mia...3308153c23.jpg
https://cimg6.ibsrv.net/gimg/www.mia...4cd7dbe8dc.jpg

Technically, you can reduce the likelihood of breaking an input shaft tooth by 50% simply by removing every other tooth.

I see no fault in that logic :naughty:

:rofl:
Except that even with only one tooth removed, the car becomes almost completely undrivable.

Update for AZ6 users:

Contacted Walter Motorsports. Asked if they were working on anything for the AZ6. They said it was on their to do list but they are busy with 5spd stuff for SCCA racers. They weren't aware of the market for a beefier AZ6 so I shared some
info and stats. They're interested so we're sending them a few boxes to evaluate and inspect.

If anyone reading this has a complete AZ6 with sheared gear teeth, LMK. We need one for science.

IIRC bbundy has about a dozen :)

--Ian

Sent him an email a week or so ago, no reply yet. Maybe I'll give him a call

Semi-unrelated: I dream of a 6 speed box that is a direct fit, can take 400+hp and cruise at 70mph around 3k rpms. Basically I'd like a beefed up factory 6 speed with a bit of a change to the gear ratios.

I don't need a box that strong and maybe I never will, but I say if you're gonna dream... Dream big.

Hmm. That is what I have with the BMW 6 speed now. Some assembly required but it isn't bad. Just bolts in.

I emailed with them a few weeks ago. They said their biggest problem was being too busy and it's a 2 man operation. Hopefully I will hear from them soon, as I keep seeing good deals on getrag 260's locally.

More input shaft carnage for your viewing pleasure.
https://cimg4.ibsrv.net/gimg/www.mia...efef1e11c2.jpg
https://cimg9.ibsrv.net/gimg/www.mia...9ba7999985.jpg
This is why I can't seem to run full power in any gear but 4th. This gear transmits power to the rest of the gears. It would be nice to have a Miata transmission in the long run, that way I don't have to figure out a neutral safety switch and speedo.

I wonder if the cryogenic treatment would add strength to this piece. I'v read a lot of serious people who swear by it, but also race with a friend who is a metallurgist for Ford Motors, who says they had tested it years ago, and no benefit; said if it worked, they'd be using it. If it does work, this is exactly the kind of parts I'd want to treat.

It's not that it doesn't work. Cryo treatment makes some difference but "cryo cycling" with multiple slow cycles yields a great benefit. But it takes time (almost a week) and money Ford probably didn't value. I've seen everything from cutting tools used to make eyeglasses to fleet vehicle brakes tested and the differences in life were substantial. Last time I was at the facility it was expanding because of increased volume of orders.

If they can beef up the overall trans, use a S15 (or FT86) 6th gear set (assuming it'd fit), and put in a 3.63 and you're there.

Do you have a complete, intact AZ6 with broken gears (other than input shaft) you can donate? Email us if you do info@949racing.com

Pretty sure @sonofthehill runs 5-speed only.

@1993z32 might be able to donate to the cause?

Thanks Sixshooter; I'v been trying to reconcile what my buddy had told me, with the shit load of knowledgable racer's who treat everything they can get off their car. Glad to be brought up to speed on this!

I don't have any of my boxes left.

Side note, if anyone is planning on beefing up the 6-speed in any way, the synchro rings, especially 4th, need to be welded to the gears. Due to the direction of the helical cut the ring separates from the gear (they are press fit) and the trans proceeds to attempt to go into 3rd and 4th at the same time. This was the only reason I lost 2 6-speeds at 350wtq, no broken teeth or anything else. (And this happened within a few pulls). Note that I was using an unsprung twin disc, some people attribute the failures to the aggressiveness of the clutch, but it's a weak point regardless.

Pictures and more in depth description of failures:

https://www.thecarpassionchannel.com/trans-fail

Sorry Emilio, I only have 5 speed boxes. All of my 5 speeds have sheared teeth on the input shaft in a similar manner. This could seem like a failure in 1st, 2nd, 3rd, or 5th, but it was always the input shaft in my case. I was going to scrap the 2 complete junk boxes I have, but those guys suggested they might still have some core value.

As I understand cryo treatment it helps more with wear characteristics than with tensile strength, not sure what the solution is.

Greg, didn't you bury those 6 speeds in your yard or something, can't you dig one up :dunno: ;)