From what i've read, the 4th gear trouble that occured on the 6 spd tranny was caused by heat.

Read up on it here:

https://www.evolutionm.net/forums/sh...light=4th+gear

https://www.evolutionm.net/forums/sh...d.php?t=210221

 

Yeah but after shep builds up the 5 speed, its basically indestructable =)

 

No, thats wrong.

The 4th gear on the MR is small and tends to break after seom abuse.

Only the 03-04 5speed realy had 5th gear problems. The people that have problems with 05 & 05 5 speeds need to learn how to drive.

 

This is the answer I've been waiting on, but I didn't want to say anything.

 

my tranny sucks... this will b the hird time i have taken it in for the fith gear syncro... fourth went out as well... well se what happenes i have a evo 9 rs

 

Honestly, do you drive it hard, or is it seriously a manufacturing defect?

 

How many miles are on the tranny? Has it been on the track? How often? Do you rev match?

 

That's a bunch of bs. So far on here, I don't think I've heard one complaint on grinding gears in the IX 5 SPD.

Mine is perfectly fine at 16k

 

I'd always heard the '03s and '04s primarily had the problem with 5th gear synchros.

 

Nope he's right on half of it. The MR tranny tends to break/warp 4th gear due to heat issues because the 6spd does not dissipate heat as well (hence the reason for cooling fins also on the bottom of the 6spd which mitsu probably knew that the tranny had cooling issues).The fact that 4th gear is also thin does not help the warping/breaking (it gets so hot the metal actually softens like crazy, due to friction), because the 6spd is the same size as the 5spd, with a extra gear crammed in there, which means no good when dealing with gear thickness, and heat. And the only time people have broken 4th gear was autocrossing (due to tremendous friction/heat buildup, and no cooldown time), nobody who DD their evo yet has broken one, and they all happened to be using BGII in their tranny which is also known to break down much easier in high heat/friction which basically causes metal to metal contact when hot enough made, (which is the reason mueller swears against bgII). You are correct about the second half of your statement though. Their were revisions made to the 05-06 trannies about the synchros, even though some people are still going through them, it's not nearly as many who had issues with the 03-04 trannies.

 

That should pretty much answer your question^^.

 

I know about the heat issue too (which leads to the 4th gear breakin), I just thought I'd make my answer simple.

 

SRT-TO-EVO is mostly correct but the reason for the failures on the 6 speed is because of the use of incorrect gear oil. An oil with a lower viscocity was used in both cases that most likely caused the failure. Yes, the 6 speed has smaller 4-5-6 gears and yes, it hold less fluid so it heats up more. The correct fluid goes a lot way in protecting your tranny, therefore only use the stock Super Diaqueen 6 speed tranny fluid at all times (75W-85 GL4). The failures also happened on track sessions that last approximately 20mins with the incorrect tranny fluid, so think about keeping your RPMs in the 4000-7000 range most of the time for 20mins and you get the idea.
Auto-x usually lasts between 30-60secs and never goes above 3rd gear so that would not cause enough stress to damage the gears. If anything the 1st-2nd gears on the 6 speed are nearly indestructable compared to the 1st gear on the 5 speed which is the same width as the 4th gear on the MR. Becareful launching the 5 speed. The 6 speed also has better designed synchronizers and thus is able to shift smoother than the 5 speed.

 

4th gear goes due to HEAT and the fact the the gear is a little thin so when it grabs it doesn't fully line up. This is very similar to the WRX tranny issues, you can see that the teeth are worn on one side while the other looks new.

 

Over heating happens as a result of using an oil with lower viscocity that breaks down and becomes thinner thus resulting in more friction, weakening the gears.