I have seen far too many 5 spd vs. 6 spd. threads out there. I think this is one of the most if not the most controversial subject dealing with the different trims of the evo. Is there a shop/person out there that has/can take one of these trannys apart and take some pictures of the gears. We need to have some visual proof behind the claims of the 6 speed vs. the 5 speed. I've seen 1 picture showing the synchros and forks. Can anyone please take some shots of the guts in both these trannys to we can lay this issue to rest?

 

PM scott from ttp-engineering he can help you

 

visual proof behind claims of the 6 speed vs. the 5 speed? Its very obvious they are different and have different gear ratios, but what controversial issue are you talking about? I think you need to be more specific since you haven't really addressed anything specificly.

 

I'm talking about the claim that the 6 speed is less sturdy than the 5. Many people say the gears in the 6 speed are physically weaker than the 5.

 

it's simple really, you're cramming 6 speeds into a space that originally housed 5.

i don't remember which gears were stronger on the 5 than on the 6, and vice versa, but i do remember this being covered by Jon of TRE (EVOm ID: GEARS) in a past thread.

Search for threads under that username and you should find some results.

 

In an arguement with "fromWRXtoEvo", "GEARS" -Jon@TRE writes:

"Now let's talk about the 5 & 6 speed transmissions found in the EVO.

The 5 speed designed & built by Mitsubishi while 6 speed is designed & built by Aisin. You probably already knew that because you own an MR and I'm sure you know the gear ratios so I won't bother you with stuff you already know.

Looking at underside photos of both transmissions one would immediately assume the 6 speed was built like a brick **** house but don’t judge the book by the cover.

Like I said earlier in this thread the shaft center spacing the 5 speed input shaft & output shaft are roughly 10mm further apart than the 6 speed. This may not sound like much but anytime you increase the shaft spacing you greatly reduce the amount of force on the teeth. However the final drive on the 6 speed is a 4.85 whereas the 5 speed is a 4.53 so there is a little more torque multiplication going on there which probably makes up for the shaft center spacing.

Here are the gear width measurements for the 5 speed.

1st = 14mm
2nd = 17mm
3rd = 19mm
4th = 18mm
5th = 18mm

Summary: Be CAREFUL when launching the car. I rarely see any breakage problems with the 5 speed other than 1st gear, it is possible to crack the teeth on the input shaft or lay the teeth over on 1st gear. For some unknown reason people tend to think that manual transmissions are immune to gear breakage from dumping the clutch yet it is common knowledge that you don't rev up an automatic in neutral and put it into Drive. The fact is you will, over time, fatigue a wheelbarrow's worth of drivetrain parts if you launch any car abusively.

Now here are the gear width measurements from the 6 speed.

1st = 19mm
2nd = 19mm
3rd = 16mm
4th = 14mm
5th = 14mm
6th = 14mm

Summary: 1st-3rd are very stout and shouldn't give you much of a problem but I'd be careful in 4th-6th. The tooth profiles on 4th-6th is dainty making for a quiet transmission. For the record the DSM 4th gear is 15mm and it's known to eventually give up the ghost, especially if you are making over 700whp so I'm skeptical about the 6 speed. In this business it's good to be skeptical. It doesn't mean that you don't agree with somone's findings, it only means that you've been doing it long enough to know that most of what you've read on the internet has a signal to noise ratio of an old short wave radio on a hot summer day. In time I will have more data on both of these transmissions and I'll happily share my findings.

As for the final drive gears the 6 speed is incredibly stout yet I rarely see the teeth on the 5 speed have any problems. The fuel economy of the 6 speed can be attributed to the 4% taller 6th gear and the narrow gear teeth yet with the CEL tune of my MR I can barely manage 24mpg on the highway.

The synchronizers on either transmission are pretty good and with a properly adjusted clutch one shouldn't have too much of a problem with them but if you are shifting it fast as you can there will come a day when it may not shift as good as it used to. Contact me if you need help.

As for Teflon cables, thinner transmission oil and the other improvements they will help make for a nicer shifting transmission but this won’t improve the strength of the transmission. If this MR wasn't my first new car I'd have the 6 speed out and the 5 speed with drag gearing and never look back."


Jon@TRE





HTH

 

hmmm, wish i found this thread earlier. Now I feel like a **** head for making this thread.