Stronger gears using different materials. Still testing on metal fall out numbers in the oil samples. Estimated cost is dependent on how many people sign on.

Michael
DTM

 

This is interesting as i've done a bunch of track events and though I haven't had any issues I really hadn't thought about changing the tranny fluid yet. I guess I will before my next one though.

Just a thought, but I'm wondering if some of this heat is coming from aftermarket downpipes. They stit awfully close to the transfer case, way closer than the stock dp did.

 

As can be seen in my thread from last night, I'm the most recent MR casualty as I lost 4th gear last night. I had fairly fresh fluids in there, but instead of my preferred OEM Super DiaQueen, I had BGII in the tranny. It got too hot and gave out in 4th, I guess. I was running hard, but this was around 8-830pm on an overcast evening where the temps had dropped down into the 70s, so I can't blame it on the 90-degree midday temps.

 

This is not good! I'm really getting nervous about going to my next road course event...

 

How fairly fresh? I thought you didn't like BG2 and used something else?

 

It was all I could get my hands on at the time. Fresh as in 2-3k miles when I had the Exedy 4-puck installed, and I have only done minimal runs on the road course (no full day events) and maybe 2 autocrosses.

 

Hmm interesting. Well, I am going to be installing a temp gauge for the gearbox as well and will run it with and without the tranny cooler running. I almost might try out different oils and see if there is any temp differences.

 

Warr,

How much stiffer than stock is your pressure plate? You are also using a 4 puck clutch. That combo and thin tranny fluid is the death for a weak tranny like the 6 speed on the MR.

I have real track proven (1500-2000 miles per year of track time) experience with weak trannies on my SE-R. I have broken 4 of them. The last one I broke was in 2004 at Cal Speedway. I kept on racing since I was leading the race and the tranny finally refused to shift and I ended up in the tire wall.

For weak trannies the reciepe is really simple:

1. Do not run a pressure plate that is too much stiffer than stock. 30% stiffer is tops.
2. Run an organic type clutch, not the four puck.
3. Use tranny fluid like shockproof heavy gear oil.

If as Jon @ TRE says that the 4-5-6 gear are small, then any stiff jolt to the gear from a stiff clutch/PP will eventually break them.

I had to learn the hard way with my race car. At first I used an ACT Xtreme pp. This sucker broke TWO of my trannies. After that I switched to a JWT pp that was only 30% stiffer than stock and to a stock clutch disk. I also ran shockproof heavy and that took care of the problem. After that I experimented with an Exedy racing clutch that was 52% stiffer than stock. BIG mistake. I broke my tranny again.

Now I am back to the JWT 30% PP and stock clutch and I could not be happier.

 

The previous ACT was 2900lbs, and this Exedy is 3010lbs, but the new Carbon Twin Exedy that will go in now is only 2100 or so.

 

nj1266,

What kind of gearbox failures? broken teeth? I think our problem is heat related not shock related. Although I agree with you, even Jon was telling me not to get too crazy on the clutch. He talked me down from a 3200 to a 2900 ACT. Fine with me since I don't do car bowling.

 

Broken teeth. The teeth on the third gear will shatter and you will lose that gear.

If the 4-5-6 gears are small on the 6 speed and the teeth shattered on your tranny, then it might be the same problem that I was having.

If it is a design flaw and Jon cannot go with beefier gears, then I advise you to get a 5 speed tranny. Aside from cryotreating and shotpeening the gears, I do not think that Jon can do much to strengthen these weak gears short of changing them.

I think the mere fact that Jon suggested the 5 speed speaks volumes about the limits of what he can do with the 6 speed.

 

It kinda blows my mind that a car that stands for Mitsubishi Racing has a tranny weaker then the normal car. I guess this might be jumping the gun a little, but it's not looking good.

 

I think Mitsu knew something as they tried to combat this problem by putting all those heat sinks on the tranny housings.

I wonder if the BG2 has something to do w/ the failures as its viscosity is on the thin side.

 

If I had more money I would for sure be getting a 5 spd. Big price difference at the end of the day however.

Approx $1500 for 6spd rebuild/shipping/fab Vs. $2925 for a 5sp with shipping and however much the 5spd shifter/linkages/mounts cost. Plus I would still get a oil cooler for either one, which is another $500 or so on top of everything.

You also have to think about the issue of ever selling the car... is it a MR or GSR or a GSR+?

 

I always thought that the 5 speed was a getrag transmission and the 6 speed was Mitsu sourced. The way it was explained to me was that Mitsu commissioned the 5 speed for the American market because of reliability issues with the 6 speed in overseas cars, and we tend to place more on reliablilty or harder on cars as a consumer group. Can anyone elaborate on that? This isn't to be taken as gosbel, just trying to straigten out my facts.