I'm looking at a couple different options to prevent this from happening again. In the mean time I'll be running putting another 6-speed in the car this weekend so I can get some more seat time.

On a side note, I picked up a hard top this afternoon. It needs some work, but I can't complain for $250 delivered.

 

Nice videos! Looks frustrating being stuck behind folks. I was noticing, in the first video, you never made it over say 6,800 indicated, most of the time not over 6,200. And that's indicated, I'd done some testing before (when I noticed in my logs I would shift at 6,700 instead of 7,200 or so as I intended) and found the OEM tach reads several hundred RPM high till about redline, when it starts to catch up again.

Is that cause it was too wet, just the heat of the moment, or more to do with an intentional matching of the shifting to the powerband?

Curious (mostly in my hunt for camshafts) what someone with ANY track time thinks :-)

 

PS - for what it's worth, the 6 speeds out of the turbo cars have treated gears. The difference in parts cost is $5, but of course, the cost to replace them is quite a pretty penny more. :-)

 

I occasionally shift early just for the heck of it. I'm not getting paid if I win. I am paying if I break the car though.

 

Jay, what kind of options are there in preventing this from happening again?

I'm curious if all that drag racing you used to do played a role in the gearbox failing.

 

It was very frustrating because I'm just getting back into driving on a track and want a steeper learning curve. That just doesn't happen if I can't push the car. Felt like I was in a parade for most of the day. In my car the tach is dead on, especially in 3rd and up. Most of it was because it was too wet and it couldn't put the power down.

I'm mainly looking at different transmissions, but I haven't ruled out building up a 6-speed with cryo treated MSM gears and stuff.

In all the time I was drag racing I expected the box to fail. I abused this thing bad. One thing that I do suspect is that is might have something to do with the oil I was running and how hot the box got. Won't know until I get it apart.

Last year I was running Redline shock proof, but it didn't shift very well. I drained that fluid and went with the Ford stuff. It shifted better and better with the more miles I put on it and didn't fail. The fluid was changed out 3 full times over a period of about 2000 miles. This spring being the last time and it was evident that any residue from the shock proof was gone. I also took the opportunity to seal up the bottom/sides of the engine bay completely and this extended all the way back to the beginning of the transmission. I'm guessing this definitely caused the temps to run hotter inside the box.

I also did a session, came in and drove 5 miles to a gas station, filled up and then went back out and that's when it failed. Hopefully I can find out more when I get it pulled apart.

 

I was slightly looking into different transmissions as well. It appears that the rx8 6-speeds can be swapped in withe the change of the bell housing. How strong they are is another question.

Gearing is just slightly different, too.

 

It's my understanding that the RX8 Aisin 6 speed is no stronger than what we have. Probably has very similar internals with a different case.

Most likely I'm going to end up with a TII swap. It just makes sense at the moment from a strength and cost analysis. Just going to go about it a bit different than most people. I'd say that it's stronger than the 6-speed based on the research that I've done and if it does break I can find them all day long for cheap.

 

True, be sure to keep me in the loop. If you decide to get an adapter plate made, im sure quite a few of us would be interested in buying one.

Best of luck Jason! I'm tossing a 99 6-speed in this weekend, lets hope it last long enough for a solid solution.

 

Will do. I'm also tossing in another 6-speed this weekend.

 

That must be it - the traction - I watched a later video (actually, where you lost 3rd) and when it was dry, you really did rev it a lot further.

That's odd. I measured, directly, the tach response. I fed it a pulse train (using the megasquirt to monitor) and recorded the tach at various steady state RPMs.

http://abefm.smugmug.com/Miata/Modif.../4706256_f8xk5

My findings:
I fed the tach known spaced tach pulses, and found that the tach is accurate at low RPM (1000), and from ~1500-~4000 is picks up linearly about 175 rpm of offset (it reads high). Then it stays there until ~7200 (reading ~7375) and by 7500 it's reading correct again, which it retains through 8000 rpm, which is as high as I tested.

Ah, ok, so it's not as BIG as issue as I thought, but it was certainly there. Very repeatable.

I'm hoping to end up right on the safe side of what a 6 spd can handle. :-\

 

Your method of measuring this is much more precise than my own. I'm only going by the few times that I have looked at the tach and verified what it was doing on the dyno. This was all in 5th gear so it's certainly not climbing as fast as it does in the lower gears.

 

Jason, if you have some money to **** into the wind, you might consider ditching the 6-puck. It will help with tranny longevity for sure.

 

Eventually I'll get to that point, believe me I want that twin disc. For now though, I'm going to throw the money towards a transmission solution of some sort.

 

You've turned it down to ~300whp for road racing, right? If you put the twin-disc in it, I bet you can make the 6-speed last. The twin-disc is going to be inherently kinder to the transmission since there's less momentum in the system - it's akin to removing your entire flywheel, plus a little bit IIRC. And then the radius is smaller, which is huge as well. No matter what you do, the twin will make it last longer.

I've been road racing at 275-300whp for about a year now, probably like 10-12 events, and my transmission is doing great. 6 months on an ACT HD 6-puck, 6 months on the 949twin.

 

Yes, it's at 16# and as little timing as I can run without the egts going through the roof. Unfortunately, I lack the self control to keep it there.

For now I'm thinking about adding a cooler to this 6-speed to see if that will help keep the temps down and add some longevity. I can make it happen for under $400 total and I feel that's very reasonable. But I'd also like to do some tests to see how hot it actually gets prior to adding the cooler.

 

Here's a picture of the carnage.

 

That doesn't look too bad. A file and like 20 minutes and you'll be good as new; just get some of those burrs off.

 

ewww, what a nightmare.
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thats painful to even look at...wow