The amount of torque the clutch holds is proportionate to the damage it can do. Choose your torque capacity wisely and don't deviate too far astray from the OEM design. OEM did all the hard work of finding out what is best suited for your drivetrain and what will help make it last a long time. If you bought the meanest race clutch expect it to have nothing to do with what is best for long transmission life and everything to do with not slipping. If the clutch doesn't slip then the input shaft must take the brunt before passing it to the next gear.  Here is a classic example of too little length of spline trying to do the job of getting power into the transmission.

1st gear features a pretty high pressure angle in order to keep the teeth from breaking off. However it doesn't like high radial thrust loads that are generated from that pressure angle. Note the brinelling of the I.D. of this gear.  This is caused by the gear pressing against the needle bearing rollers during those big clutch dumps.

Also note that this EVO-7 1st gear was not properly heat treated. This gear was shot peened to show how the shot brinelled the surface. This is commonly found on 1st and reverse gear but not exclusive to these two gears.

The inner sleeve and roller bearing both suffered damage from the extremely high radial thrust load exceeding the material strength.  This is not commonly seen on the older DSM AWD transmissions because the pressure angle isn't as high.

There is more than one way to drop the transmission out of a high power EVO.  This way used a triple plate carbon/carbon clutch that held over 800ft.lbs of torque, a Motech ECU set-up with the bang-bang anti-lag @ 6500rpm and a rookie dumping the clutch.  The quickest time that this EVO owner had ran this day at the dragstip was mid 13's.  It takes more than money to get an 800WHP EVO into the 9's.

Notice again what too much axial & radial thrust load can do to an EVO transmission. This transmission didn't need to be unbolted to get the internals out of it. Be careful getting it from a dig.

The EVO-4/91st gear is narrow. it's .080" narrower than a 90-99 DSM 1st gear but it holds up pretty good because of the high pressure angle.  However, it's also the reason the case split in the photo above.  The radial thrust loads generated by the pressure angle will yield the transmission case.

Note the cracks.  Yes it's bad.

Here is the input shaft 1st gear teeth that ran with the gear above.  Notice how worn out the teeth are, there is .010" worn off the face of the teeth and yes the teeth are also cracked.

Make sure to use the correct transmission oil in your EVO.  Synchroshift/mesh type oils are NOT to be used regardless of what people may tell you. Recommended oils can be found on the FAQ section of this site.

These are pinion gears. 

The gear on the left is from a Ford Mustang with an 8.8 rear end.  Yes, people do manage to break them from time to time too.

Note the size of the gear teeth when compared to the pinion gear inside of an EVO transfer case. You will want to learn how to let the clutch out gently, avoiding shock loading, if you want the transfer case to live.

A flimsy transfer case housings and poorly adjusted contact patterns will crack the 4718H ring gear in a hurry. We shot peen our gears improve durability.

The front differential works great for road racing, autocross or just daily driving but it has 3 things wrong from a design stand point that keep it from being worthy for drag racing:

1. Crappy cast housing with lots of stress risers.

2. Tight corner radii.

3. The above two flaws are also located directly on the gain boundary of the induction hardening for the splines and these are all things that we can fix.

Some people will find that lots of pricey items can and will get destroyed if the hollow splined transfer shaft shits the bed.  There are stronger transfer shafts out there and we recommend them however, there are many other parts that can and will fail besides that transfer shaft if you use a clutch that holds too much torque.  When choosing your clutch make sure to read this page.

It has been said that shit rolls down hill...

We can fix this.

and when it comes to the EVO it's an avalanche until you learn how to get the car off the line without killing it.

Some people understand that you don't want to launch the balls off the EVO but think that barking the tires into 4th gear with that no-lift-to-shift ECU mod was ok to do over and over and over again.  

Both input shaft and output shaft were bent a combined .043"

Your EVO transmission has pretty good synchronizers and can take it's share of fast shifts.  However, if your clutch isn't releasing, the blocking teeth on the synchro will block the shift from being completed until speeds of the various components are going the same speed.

If you're hell bent on sending into a gear before speeds are synchronized you will break off the blocking teeth like this guy.

Here is a text book example of what the 1st/2nd synchros will look like if your clutch is not releasing properly.  Note how the synchro stops are deformed.  Tapering the stops does not work as it'll only have less material to mush out of the way.

This is the 3rd/4th synchro assembly from an EVO.  Notice that the hub is busted.  This happens when the synchro tries to block the shift and the driver forces the transmission into gear.  There is not a twin disc on the market that can outshift a single disc clutch.  If you road race please consider using a single disc clutch or a twin disc clutch that has proven itself worthy for road racing.

2003/4 EVOs were plagued by chipped teeth on the final drive gear.  A new part number gear exist but this gear still needs corner rounding to make it live in a high power EVO that lives a 1/4 mile at a time.

Make sure the little O-ring is between the transmission and transfer case when installing the transfer case. If you don't oil will leak out of your transmission.  Also, don't wrap your downpipe past the oil pan because it can soak with oil and act like a wick, burning your car to the ground.

If you are leaving oil drips in your parking spot and the underside of your car is getting an oil bath you should find out where it's leaking from.

This is reverse gear from an EVO that was driven will low on oil.

Yes that is a tapered roller bearing on top of the gear. One would think that the driver would have stopped instead of trying to drive home just to avoid having to be towed.

It took so much power to turn the transmission that the driver had to downshift to 4th gear and get into the boost just to drive home.

Eventually 4th gear started to slip but they couldn't downshift to 3rd gear because the hub & sleeve had pair bonded.

Don't be afraid, just use your head.