dang more and more MR owners are regretting buying MR's because people keep on scaring them about 6 speed 4th gear failures and other threads like this. it sucks but i guess people need to do more research before they buy thier cars. some of these people even have selective reading.. They can see all what people post they only chose to see that 4 gear breaks. they fail to see that it breaks because of the heat on road racing. damn im tired i need some sleep!

 

As long as I can decently mod it and drive hard from time to time I'll be ok.

 

I think I can react how ever I want..It's a freaking EVO, it's supposed to be a Performance Car!...So when I hear crap like 4rth gear going out and I see with my own eys other Evo owners having problems I have the right to be pissed!.

 

I'll find out! I hope not!

I'll be running my TRE 6-spd with cooler until it breaks again. Once that happens i'm putting a automatic trans from a ford mustang in.


I was running the stock clutch and restrictor at 31,000 miles when I ripped the teeth off 4th in my 6spd. So.... next!

 

A buddy of mine had a 9 MR his clutch went out at about 10K then he replaced it with an ACT with lighten flywheel. A couple of weeks later after the clutch break in he started having problems shifting from 5th-6th driving and even at idle. He really didn't do any hard driving or racing. Took it to mitsu and they voided his warranty because he had an intake! He then took it to a shop they stripped the tranny apart and his problem was I think the shifter link that goes over his 5th and 6th gear teeth had broke and it also damaged some of the other gears teeth if i remember correctly. In nutshell, the shop's conclusion was that it had nothing to do with his driving it was just a mitsu defect from the get go! Kind of sucks!

 

The 1-3 gears in the 6 speed are indeed "larger" but this by no means makes the transmission stronger or as strong as the 5 speed. There is ALOT more to a transmission than just "gears". I do not know enough particularly about the internals of the 6 speed to say for a fact it is any weaker/stronger than the 5 speed. However I do know that there aren't any in existence (that I know of) holding alot of power. Warr made a bunch of drag passes on a pretty much stock car, which doesn't say much. The fastest MR is what, in the 11 second range? Perhaps more people choose the 5 speed for drag racing because there are more of them ($), and the gears are taller (better for drag). However you would have figured there would be at least one person running decent ET's on the 6 speed, but there are none to speak of. Warr have you spoken with Shep about his personal opinion on the 6 speed? I know the 1-3 gears are beefy, but how about the overall structural integrity of the transmission (case strength, bearings, shafts, etc.)? To make room for another gear there probably would of been some type of compromise/modification in overal case thickness (or maybe the 4-5-6-R gears are just really skinny) which could take away from high horse power reliability (i.e. the case may twist or crack under severe load). This is all just speculation however...I wish someone like Shep or TRE would chime in with some real facts about the 6 speed. The only thing we know for sure is that it has problems with heat dissipation, which really doesn't relate to drag racing.

 

i read somewhere that, the 11 sec MR has a 5 speed tranny in it.... it's tha things that make you go hmmmmm......

 

And why would you suggest doing that? You and I attend track days together ... my tranny hasn't had a single problem yet.

Actually that is not quite correct. Torque is what breaks parts and different gears being of different width can only hold a certain amount of torque before they fail. Therefore it is always a good idea to determine how much power a tranny can hold based on the weakest gear. The last time I spoke to Jon @ TRE, he mentioned that the 4th gear which was the weakest could only hold a dynamic torque rating of 380ft.lb after the stress testing he did. That means stay below 380ft.lb of torque at the crank and you should be fine. If you produce more than that, your 4th gear will give up. Now by comparison the 1st and 2nd gear for the 6 speed are almost indestructable because of their width (figuratively speaking).

How that converts to wheel torque is the hardest to figure out. To be on the safe side I always use a drivetrain loss of 25% (because of AWD) which gives us a wheel torque rating of 285ft.lb at the wheels. Some people use anywhere from 18%-25% ... I ususally tend to over estimate and be on the safe side. Using 18% drivetrain loss gives you 311ft.lb at the wheels. So the 6 speed can hold anywhere from 285-311 ft.lb of torque. As far as I know both Warrtalon and Razorlab were producing torque in excess of that amount. The type of gear oil used also greatly plays a part in this whole process. By using the wrong gear oil they had also weakened the gears torque limit by increasing the friction = more heat generated.

In comparison the 1st gear on the 5 speed is the identical width (14mm) as the 4th, 5th and 6th gear on the 6 speed so be careful if you like to drag race and launch the car. But the reason why 1st gear won't be as big an issue on the 5 speed is because you don't apply that amount of torque for extended periods of time as you would on the 4th gear on the 6 speed on a race course.

Now there are things you can do to strengthen the gears, shot-peening and cryo-treating them helps somewhat but only depending on the type of material the gear is made out of.

I'm going to post this same thing in the other thread.

 

I heard the 6sp is made by toyota. -_-

 

It's made by Aisin, which is a spinoff of Toyota or something like that.

 

Is it possible for someone to make a custom gear set to equal out the size of the gears?
I guess the problem would be cost cause most people would then just buy a 5-speed.
I actually like the 6 speed better in terms of feel, it's a shame I have to worry about it
everytime I goto the road course.

 

DaWorstPlaya,

From an engineering viewpoint what you have just said makes very little sense. You're proposing using a part with a Factor of Safety (Strength of Component / Load on component) of less than 1.25. Even if you satisfy all the conditions set in engineering for using a safety factor of 1.25-1.5, which is the MINIMUM spec'd safety factor available, you'd have to satisfy the following:

Material properties known in detail.
Operating conditions known in detail
Loads and resultant stresses and strains known with with high degree of certainty.
Material test certificates, proof loading, regular inspection and maintenance.

There is no way any Mitsubishi fabricated gear falls into this category. Just because you haven't had any failure doesn't mean you won't in the future, and more importantly that another gear / trans subjected to the same stresses as your gear / trans would not have failed by now. You could have that 1% gear that happened to be fabricated slightly above spec.

 

DrSmile,
The strength of the material in being used for 4th gear comes into play. The design of the gear, the tooth profile, the width of the gear, the type of material used, the type of lubrication used, the amount of wear the material sees over time, the amount of shock you put through the gear by dropping the clutch all come into play. The TQ value I spoke of was derived from some static stress tests Jon @ TRE did. If you want specific detail please feel free to contact him.

Please understand I wasn't trying to break this down to exact engineering, wrt the specific environment the material is under before it fails but give more of a rough idea to people. But common sense still comes into play, there is only so much torque a gear can hold under certain perdetermined conditions before it fails. You also have to take the margin of acceptable error for a part that is produced, naturally some may be stronger and some weaker. The gears in the 6 speed range from 19mm width (1st) to 14mm width (4th, 5th and 6th).

I know the exact torque amount is not written in stone because there are various factors that effect how much torque a gear can hold, type of tranny oil (friction), what type of sustained RPM the gear sees (higher rpm = more friction = more heat generated), duration the torque is applies to the gear (longer it is applied the more fatigue) and shocking the gear with abrupt clutch drops. All these factors can't be determined in a dynamic scenario, that is true, go over board on any one of these and the gears will fail sooner. But what I was trying to do is give a safety range in WTQ (may not be exact) but at least something people can use to determine if they need the 5 speed for their application, provided they drive like a sane person.

Naturally a person that drives smoothly will make their tranny last longer than one that beats on it.

The analogy, I like to use is, if you use a tiny hammer on a gear and strike it a crap load of times, you may not even cause a dent. If you used a large hammer, you may be able to break it after a number to strikes. If you use an even larger hammer you could shatter it on 1st impact. I kinda think of torque that way.

I would hope and Aisin did their homework before they decided on the design and choose the materials used to construct the transmission. Why do you think it wouldn't fall into that category, because of the dynamic conditions seen inside a tranny or the cost involved? I'm sure they would know the property of the materials used in creating the gear, brittle or soft, what its elastic limits looks like. The torque through the rpm range would give them an idea of what kind of forces the gear would have to endure. I'ld hope they tested this over time with some data. I sure there was some minimum level Quality Tests the gears had to pass before they were put in the transmission. What are your thoughts?

 

Ahhhhh ! You've seen through my evil plan to buy up all the 6 speed transmissions people would sell !

 

Guys. I need some help. My friend just pointed out to me that The oil mitsu sold me is for the transfer case, and that it should NOT be in my transmission. What is the part number to the 6 speed transmission fluid? Did a search but there were just way too many threads.

I went to mitsu about a month and a half ago and told them i needed to buy tranmission fluid for my 2005 Evo MR 6speed. They handed me over a tin that said LSD gear oil and I asked them, "are you sure this isn't for the differential?". They told me, "no, that's what goes in the transmission too".

It's been in my freshly rebuild TRE spec transmission a month now. I feel like I could go over there and just knock the guy out who sold it to me.

I've gone to the track 2 times and launched the car 8 times on this fluid. Are there any largely bad effects for having it in my transmission or what can happen? I will go to my dealership as soon as I get off work and explain what happened to the GM there.

I hope nothing bad happens to my car again