THINK THAT YOU NEED A TWIN OR TRIPLE DISC CLUTCH THAT HOLDS A BAZILLION FT.LBS. OF TORQUE?
READ THIS FIRST!!
INPUT SHAFT SPLINE WEAR
It has come to our attention that many people are experiencing problems with twin disc clutches tearing up the splines on the input shaft. Shown below are two input shafts; the photo on the left is an EVO-9 that had a triple disc clutch and the photo on the right is a 97 DSM FWD that was ran with a twin disc clutch. Both input shafts were new and had less than 2000 miles on them. This sort of spline damage is terrible and causes the clutch to not disengage properly, clutch and transmission chatter and eventually the splines will strip out.
The spline wear is the result of the clutch disc not enough having enough spline length making contact with the input shaft to keep the splines from yielding from the torque and the fact that the transmission was never designed for the strain of a multi-disc clutch. This problem is compounded by the lack of a sprung damper assembly and low mass flywheels that don’t carry enough momentum to keep destructive 4th order harmonics from beating up the transmission parts. Other contributing factors that will damage the input shaft are: stroker engines, low mass flywheels, engines that have poor idle quality, sloppy worn-out engine mounts, excessive backlash in the drivetrain, general abusive dumping of the clutch, time in general and ultimately a clutch that either doesn’t have enough area of spline to handle the strain.
Other components that get ruined are:
Synchronizers
Hub & sleeve assemblies
Load bearing surfaces
Synchro keys & springs, etc.
In other words, all things that will effect how well the transmission shift.
If your application truly requires a twin or triple disc clutch, please select a clutch that has a one piece splined section or a clutch that has enough surface area to handle the strain and keep the input shaft splines from getting destroyed as this sort input shaft spline damage is not something that is not covered by the warranty. It is your responsibility to do the research and find what clutch is truly best for your application.
GEAR DAMAGE
Excessive torque will not only damage gears in your transmission but nearly everything that transmits power to the pavement. You can usually get away with shoving a ton of torque into a transmission that wasn’t designed for it but eventually you’re going to find that nothing is truly bulletproof. Click here for more info.
RECOMMENDED TORQUE CAPACITIES
When choosing your clutch make sure that you choose a clutch that has an appropriate torque capacity for the application. This value should be about 20% more torque than what your engine makes at the crankshaft but no more than 50% higher than the fatigue/endurance limit of the transmission. Using a clutch that is past the recommended torque capacity will greatly reduce the service life of certain drivetrain parts.
Listed below are the fatigue limits for some of the Mitsubishi transmissions. The fatigue limit is also known as the endurance limit and it is considered to be where fatigue related failures will not happen for at least 100 million cycles as long as the transmission is in good working order with proper bearing preloads, correct oil and with gears that aren’t worn out or making abnormal contact patterns. It is important to note that while most automotive transmissions can be subjected to loads that are 50% greater than their rated capacity these shock loads must be kept to a minimum for long life.
Rated torque capacities:
3000GT VR4 5 speed AWD W5MG1 = 440 ft.lbs
EVO-10 5 speed AWD W5M6A = 415 ft.lbs
EVO-4/9 5 speed AWD W5M51 = 375 ft.lbs
EVO-8/9 6 speed AWD W6MAA = 290 ft.lbs
DSM 91-99 5 speed AWD W5M33 = 245 ft.lbs
DSM 89-90 5 speed AWD W5M31 = 228 ft.lbs
3G Eclipse 5 speed FWD F5M51 = 375 ft.lbs
Eclipse/Lancer 5 speed FWD F5M42 = 300 ft.lbs
4G Eclipse 5 speed FWD F6MBA = 280 ft.lbs very under rated.
DSM 91-99 5 speed FWD F5M33 = 245 ft.lbs
DSM 91-99 5 speed FWD F5M31 = 228 ft.lbs
DSM 91-99 5 speed FWD F5M22 = 160 ft.lbs
Mirage/Colt 5 speed FWD KM210 = 150 ft.lbs
Mirage/Colt 5 speed FWD KM176 = 130 ft.lbs
Again the fatigue limit is where there won’t be a failure of gear teeth pretty much regardless of how many cycles the parts is subjected to, assuming the transmission is in good working order with proper bearing preloads, correct oil and with gears that aren’t worn out or making abnormal contact patterns. One of the best things that can be done to improve strength is to shot peen the gears. It has proven itself invaluable when it comes to increasing the amount of abuse your transmission can withstand before failing.