cul8tr

iTrader: (19)

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

Badog

iTrader: (4)

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.

Warrtalon

iTrader: (6)

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.

Badog

iTrader: (4)

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

RazorLab

iTrader: (8)

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

Warrtalon

iTrader: (6)

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.

RazorLab

iTrader: (8)

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.

nj1266

iTrader: (6)

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.

Warrtalon

iTrader: (6)

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.

RazorLab

iTrader: (8)

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.

nj1266

iTrader: (6)

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.

Mike01gsr

iTrader: (33)

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.

marksae

iTrader: (12)

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.

RazorLab

iTrader: (8)

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+?

sasquatch

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.