Road Race Engineering's Wavetrac Front Limited Slip Differential  Information


Patent pending Wavetrac® design automatically improves grip in low traction conditions. This feature is truly innovative and unlike any other torque biasing diff design.
Superior Materials and Construction:
Made in the USA   -   9310 steel gears run in case-hardened billet steel bodies. ARP® fasteners used throughout.
Limited LIFETIME Warranty:
All Wavetrac® differentials include a transferable, Limited Lifetime Warranty.


Enhanced No-Load Bias Ratio via its Wave Design Center Pack

One of the known shortcomings of a typical torque biasing differential like the Quaife is its loss of drive (behaving much like an open diff) under zero or near-zero torque conditions (for example, when there is 'no-load' applied through the drivetrain, either at vehicle stationary and/or transition from engine driving vehicle to engine braking and back).

The Wavetrac® differential uses a patent pending design to improve grip in low traction conditions. Precisely engineered, converging / diverging wave profiles are placed on one side gear and its mating preload hub. As the two side gears rotate relative to each other, each wave surface climbs the other, causing them to move apart. This imparts an increased normal force through the side gears, increasing the bias ratio as a function of load. This increase occurs automatically only when conditions find it necessary, and it 'reverts' back to its nominal bias ratio quickly and seamlessly, maintaining optimal drivability and performance at all times. It's like having two differentials in one: you get the benefit of a higher bias ratio when needed without detriment to the car's handling.


Interchangeable Friction Plates Provide Controlled Bias

Here's something else you won't find in any other design:

The Wavetrac® diff's behavior can be altered in the field to suit your needs. It comes standard with carbon-fiber bias plates for the best all around performance. Interchangeable plates using materials with different friction coefficients to fine-tune the bias ratio are sold separately.

These friction plates provide a mechanism to tune the response of the differential as a function of applied torque load. The applied torque load manifests itself as an axial load from the differential pinions into the housing. This axial force is then considered a normal force into the friction plate, and as a function of the effective coefficient of friction, will provide a resistive torque to the rotational motion of the differential pinions. The resistive torque will add to the resistance of relative rotation of all components within the differential. The resistive force, however, is non-uniform since it is a function of the axial load from the differential pinions. The unbalance of the resistive torque will manifest as non-uniform energy absorption within the differential causing a bias ratio.

Superior Design, Materials, and Construction

Designed from a clean sheet, the new Wavetrac® Differential brings current gear technology to the market. Internally, its gear tooth forms are optimized for strength and improved oil film retention over competitive designs. Our gear package is smaller, reducing overall mass, yet is more durable. Attention was also paid to the side gear/axle interface, putting as much material thickness as possible in this critical area - most important when power levels get high.

Each Wavetrac® Differential is crafted from the highest quality materials available. The internal gears are made from high strength 9310 alloy steel. The diff bodies are machined from case hardened steel billet. To complete the package, every Wavetrac® differential is built exclusively using high quality, high strength fasteners from ARP®, the world leader in fastener technology.


EVO Installation:


There are three components inside the transfer case. One is the ring and pinion gear set that allows the power to change direction and head down the drive shaft to the back of the car. The second is the front differential. The third thing in there is the viscous coupler for the center diff (the center diff actually lives back inside the tranny).

The thing that most people break inside the transfer case is the spider gears in the front differential. Dude goes and practices his launches, gets some wheel hop and breaks the spider gears in the front differential. He goes to the dealership and they tell him he needs a new transfer case for $2k+. Thus the thinking that the transfer cases are weak. Some people have had trouble with the ring and pinion gears, but most trouble is with the front differential.

Busted Stock Front Diff

Mitsubishi had Getrag of Germany build the transfer case assembly for the EVO. This is normally a good thing since Getrag builds some nice stuff. But also Getrag has this thing about not selling service parts separate. Everyone always cries about this after the fact but how many of you axed about it before buying the car?

This front differential will give you better traction coming out of a corner, yes. But most importantly it will prevent you from busting up your stock weak front diff, or if you catch it right away allow you to salvage your transfer case assembly by replacing just the differential. You can buy this diff before or after you blow up your stocker. But you will buy it if you are going to have fun with your car.

Stock diff on the left, Wavetrac Limited Slip Differential on the right.


Originally Posted by steve_evo
Does the diff need to be re-shimmed to be aligned properly inside the t-case or is the install simply to remove and replace?

The Wavetrac Limited Slip Differential goes deep inside the shimmed part. Reshimming is not necessary as long as you only change the front differential and dont swap any other parts.

Mike W


Originally Posted by Chris in HB
2 questions (for Robi or anyone else qualified to answer):

1) Would I need to upgrade my t-case with only 300-320 whp? (I would assume not)

2) Do I need to upgrade the t-case with a Wavetrac front LSD? (This one I'm not sure about)

Thanks in advance.
1) You can bust up the stock front diff on stock HP if you are beating on the car and get wheel hop. Shock loads break the spider gears, not torque. You could make 600 wheel HP on a dyno and not kill the diff, but with 250 at the wheels and get some sharp grip/slip/grip and it will break.

2) I dont know what an upgraded transfer case would consist of other than a Wavetrac Limited Slip Differential or other stronger front differential... no one makes any upgrade parts do they?

Mike W


Originally Posted by nsnguyen
I asked around at different shops in the area and it looks like installation is going to be right around $700, and that if you were going to get your clutch done, then would be the perfect time to do it.

Those shops either have a $200 an hour labor rate or they dont know much about EVOs. We'll be charging about $350 for the install for the diff alone, or maybe another $200 labor along with a clutch job. But then we are used to charging broke ass DSM college kid labor rates and we dont see EVO guys as a cash cow to pillage.

Mike W

Originally Posted by marksae
What if we put new bearings on the diff? Might we need a new shim to get the correct end play?

The diff it's self has no bearings on it. It just kicks it inside the carrier. There is nothing to press on or off it so there is no bearing to replace. Even if you really really wanted to put new bearings on the carrier, remember back to the part where the entire assy is made by Getrag and there are no service parts available other than seals.

It would be a good idea to have some seals on hand for the install. I have seen gorillas pinch them and sometimes when you take them apart they just go all wonky and expand making them a pain to put back where they go. There is no silicone sealant to seal it all up, they use big o-rings everywhere.

The transfer case has hypoid gear oil in it for the ring and pinion gear, and there is also tranny gear oil inside the differential carrier in the center of the transfer case. So the oils need to be kept separate with all the goofy o-rings.

Mike w


Originally Posted by marksae
After taking the driver’s side axle, does the EVO t-case come off just like a DSM t-case?

Kind of. To wrangle it out of there you have to take the rear section off. Because the whole tail section of the transfer case goes over the top of the crossmember it is a big pain.

If you are careful you can leave the transfer case on the car and only take the side cover off. The carrier just slides right out then. You have to be careful putting it all back together to not pinch any of the seals or you will mix oils and get strange leaks. Just respect it all and be mindful of all the seals on reassembly and there would be no reason to take the whole thing off.

Mike W

Originally Posted by EVO_RPM
This LSD is a direct fit isn't it?

That's the whole point yes.

Mike W

The diff does fit in the RS, MR and all 05 and up cars. Also fits all the way back to the EVO 4-7 cars.

Mike W

Originally Posted by nsnguyen
OK, let's say you're kind of a dork and got these six inch Wavetrac Limited Slip Differential die cut decals in dark silver for your car. You have two of them. Where do they go? On the decklid? ON each of the front fenders below the indicators? Just a hypothetical question... not that anyone I know would put DECALS on their car....

Since the Wavetrac Limited Slip Differential is a Torsen type differential, it all works all opposite of what you would normally think. If you put the stickers on the front of the car anywhere, the car will oversteer horribly. Put them on the rear 1/4 panels or bumper and it will push and plow like a pig. Through extensive testing and taking into account the weight bias of the EVO, we found that you need to stick on the sticker on the driver's side just under the side mirror. On the passenger side you need to put it right on the door seam between the front and rear doors (but down low).

Mike W


Here is seal info:

Kit #1

These are the seals that I would want to have if I was doing the install. They are the main o-rings for the transfer case cover. They can swell and get weird and are cheap. We are including them free with every EVO Wavetrac Limited Slip Differential diff we ship.

MD752659 o/ring, t/f case
MD743612 o/ring, t/f case

Kit #2.

The internet told you that you need a bunch of seals. These are the additional seals that a ham fisted gorilla might kill when wrestling with the parts at odd angles with oil dripping on your face. It additionally includes the two inner seals that keep the transfer case oil separate from the transmission oil. Also an o-ring between the transfer case and the transmission that could get pinched when removing and installing the transfer case. Cost is $17

MD727944 O-RING, T/F CASE 82.7

Kit #3

If for some reason you want every seal that the mechanic will come in contact with, these are them. It is all the parts in Kit #2 and it additionally includes the two axle seals, the transfer case driveshaft seal and one other small o-ring to the tranny. Cost is $32

MD727944 O-RING, T/F CASE 82.7

Remember, we are shipping the first two o-rings for the cover with every diff free, they are not listed in the 2nd and 3rd kits.

Mike W



Originally Posted by nsnguyen
OK, so now that I can see the transfer case diagram, I have a question. It looks like the VCU sits between the ring gear and the front diff. If so, how does it limit the center diff action if it's outside the center diff?

You just gonna have to trust us on that. I dont have that much typing in me. But somehow between power going back and forth 6 ways through 12 different shafts and sleeves it gets done.

Mike W