6 speed transmission #4 go boom.
 

This time new failure mode. Stripped second gear instead of 4th this time. Newish 275 A6 hoosiers nice 80 degree day on a super grippy lot. Car was ridiculously fast until that happened near the finish of my first autocross run.

Sure wish somebody would make a proper solution with good gearing for this weak link.

whatever happened to your s15 box project?

I still got it I just havent put in the effort yet to work out the details and Im trying to keep the car running week to week as Im racing it.

Have you torn it down yet? I'd bet 4th gear only survived because you weren't using it this weekend. If 2nd had held together, 4th would have blown for sure on the first day of the NASA TT this weekend.

How much torque do you run with the auto-x boost setting that you nuked 2nd gear?

I do run less power for NASA than I do autocross. I turn the boost down.

This transmission might have been a little suspect as I built it myself out of two damaged transmissions. The first transmission I broke actually had a thrust retainer failure and the gears were fine on one of the shafts where as a 4th gear strip out takes out the other shaft.

It's about 310 ft-lbs from 4300 rpm to 6500 rpm. graph is where I have my boost cut set so its a bit under that.

https://www.miataturbo.net/attachmen...0139_small-jpg

Just finishing up my build and found this post and the other 6 speed post. These two post have me worried and after some research I found this. Seams like a good high HP and T fix. I emailed them and I
Was informed this will fit in the Mazda box. They will even make custom hear ratios. It's a lot cheaper then the Nismo box as well.

http://www.par-engineering.com/Products/Catalog/ProdID/410/CatID/120/FS6R92A_1st5th_Synchromesh_Engagement_gearset.aspx

I believe Emmilio tried to get something out of PAR a while ago. don't knowo if that is who he has been talking to more recently. that is the 5 speed not the 6.

Bob I have some ideas on transmission stuff. You might entertain the ideas. Shoot me a message.

It is for the 6 speed AZ6 they don't include the #6 gear. For an extra charge they will. These are the hp levels they quoted me for each. Should hold up. At the bottom of the page they post the standard gear rations. I will have to call Emilio to see if this is the set he was looking at.

" Hi,
Approximate ratings for each,
Dog sets 1000hp, 800Nm
Synchro 800hp, 650Nm.
Are you using the gear set for street driving or purely track use?
Since the transmission is an Aisin the same as used in nissan and mazda certain models besides the input and output shafts the prices can be found on ur site,
http://www.par-engineering.com/Products/Catalog/CatID/120/S15_Silvia200SX.aspx "

bbundy is Bob.. ;)

I don't know much about it since I haven't had to look into this at my power level but I've heard more than one time about the RX-7 trans mounting up with an adapter plate and handling much more power. Not a good solution? Bad gearing?

-Ryan

Bad gearing and heavy was what I heard. And requires custom parts at input and output ends. A custom gearset in a factory box would be perfect in many ways.

The 6 speed aint exactly light, its like 12 pounds heavier than the 5 speed. Almost 90 pounds.

PAR does make 6 speed gearsets in either synchro or dog setups. It is 6-7K for the gearsets. So not exactly cheap. If emilio wasn't working on a cheaper set of gears I would have gone this way, but I have a couple of extra 6 speeds so I am not in a big hurry.

for that kind of money just a bit more gets you a sequential box.

6-Speed Heavy Duty In-Line RWD Sequential Gearbox with Helical Gears

Only 375hp though, and needs a bell housing.

Quaife makes a BP bellhousing, IIRC. The QBE69G box is rated for more torque as well. Bring your checkbook to the tune of $10-12k for a QBE69G + bellhousing + diff mount + driveshaft + trans controller.

Yeah it was like 12K or even more if you wanted other bells and whistles when I priced it out for the QBE60G. When I talked to Quaife in the UK they seemed to think that the QBE60G would be sufficient. The QBE69 was like 13K alone for just the transmission.
The bellhousing is not made by quaife, when I called Quaife USA they said they didnt make one but Quaife UK gave me the information, I have it written down somewhere.

And a Quaife box is never perfect the first time out. Be prepared for adjustments and improvements after 5-10 hours (a couple times).
Quaife and Elite are low end racing boxes...

PAR gears in the AZ6 is a different ballgame of complexity (but can be assembled less than perfect of course).