I know that several locking diff threads already exist on the Engine forum, including a sticky. I'd like to discuss this from a handling perspective on a board where I know who I'm talking to.

I'm seriously thinking about ordering a locking diff; either, the Max-Lock or the SCCA legal rebuild. I'm not sure which is right for my needs and I'd like some input:

My car is 99.9% street-driven. It is driven with some enthusiasm - stock tires lasted ~7500, Hankook Evos won't make it past 12K, third set of pads in 17K miles. Just as my car isn't tuned for max power, I'm not looking for max theoretical performance. I'm looking for drivability, control, and ultimately fun behind the wheel. I want a car that I can easily control, a car that's faster and more fun as a result of the mod. I don't have the skill to fight the car.

My Evolution is driven from March to November in Upstate, NY. As long as there's no salt on the roads, the car is out. This means freezing temps, at times, and always less than favorable road conditions. Heavy rain and light snow are the norm in the spring and fall. There are no consistently smooth roads to speak of. It sits on factory Bilstein suspension and Whiteline F/R anti-swaybars. It plows at 9.5/10. As it's a street-driven machine, I'm comfortable with that balance.

Knowing the situation and my constraints/concerns, which rear diff would you suggest?

 

you can rearrange the friction discs and plates in your stock diff as per the service manual. (they were assembled incorrectly from the factory).

took me a couple hours, and a night and day difference. welcomed power on oversteer now.

cheers, its basically a free mod.

 

^^^ This is essentially the SCCA legal diff. I'm undecided between this option and the Max-Lock.

Let me say this right off the bat; I want a professional effort. The diff will be built by someone who's done it more than once (not me) and installed by STM.

 

I'd say the max-lock as the tighter shimming/tolerances should make it more reliable.

 

im glad you brought this up, as im in the same boat (even on the same suspension setup)...and from what ive read i think the TRE is the best overall diff setup based on what ive seen. But im interested to see other opinions.

 

I would have some one do the "free mod" you wont make use of the 12 pate although it is fun in parking lots

 

Have TRE build you up a 12 plate but if you're trying to stay in a certain class, call up TRE and see if he can just re-arrange your plates.
http://www.teamrip.com/EVOLUTION%20R...20SERVICE.html
Everything will be done to that diff except the 12 plate.

 

Why wouldn't I make use of the 12 plate?

It's not a matter of staying in a given class. Truthfully, for the amount of time I spend auto-x'ing, it just doesn't matter. I undecided as to which would be better for my application and driving style. Does one have a more linear response over the other? Is the Max-Lock going to get me in trouble on the street faster than the SCCA legal diff? That's kinda what I'm getting at.

 

This is something that you should ask yourself because we don't know how you drive or how you want to drive. For sure, the 8 plate mod is worth doing because it reduces understeer a lot and, from what I've read, it makes the car more neutral.

12 plate is like the 8 plate mod but it locks up more easily, locks up faster and locks up harder. I currently have a 12 plate and the rear end whips out really well. Since I'm only on Swift springs and stock struts and stock sway bar, the car doesn't whip out that easy and you would need to put effort into going sideways. It is much more harsh on the street to just daily drive it around but friction modifiers can help you in this situation (I don't put friction modifiers in mine because like the way my rear diff locks up easily). The 12 plate is very street-able still but it's still aggressive and takes some time to drive with. There are going to be times when you're making a U-turn and you would have to give it more gas and play with the clutch to make it go forward.

As for getting in trouble in the street, no. It's not illegal to have an LSD and have it working to drive your car in the streets. Unless you were street racing or messing about in a parking lot, you won't get in trouble.

 

I had mine done by Shep...very similar 12 plate service as TRE. My Evo is primarily street driven and I'm far from maxing out the setup too (26 psi on HKS 7460 and pump gas). Not free but it is a little cheaper than TRE. The rear wheels lock up pretty easy with moderate to aggressive turning--understeer is greatly reduced and depending on how aggressive you get, you may have to countersteer a bit but it's far from being a RWD.

I saw in another thread that even if you rearrange the plates, the diff operates as a 1-way. However, if you do Shep or TRE it will operate as a 1.5-way. Something else to consider...

 

If you had to do it over again, would you opt for a diff with a little less lock?

 

subscribed, always been interested in this.

 

I ordered the 12 plate max lock from Weir on monday I'll post up when I get it in to let all of you know.

 

No..it's really not that wild. Even an aggressive turn can be controlled. There are more aggressive units like a Cusco or a 16 plate option. Those are probably too wild for the street.

There's a youtube clip of someone demonstrating the 12 plate in an autocross course..I think if you search "TRE 12 plate" it's the first clip. Take a look..he goes through a normal and aggressive turn on the course.

 

Night and day difference my ***. It helps slightly with understeer but it didn't help break the rear end out like I was hoping it would. Have you event tested it?