I brought my car in for an inspection shortly after purchasing it a couple months ago. The shop put it on the lift and put the car in first gear. The applied pressure to each wheel to test if the LSD was working. They said the rear LSD is acting like an open differential. Does this sound like something doing the TRE or Weir 12 Plate would fix?

 

Just re-arranging your plates around will help the rear diff be more LSD like. A 12 plate will help the rear diff lock up faster and harder, even making it act like a 1.5 way.

 

The clutches in the rear diff engage when you are putting power down, not when two mechanics are spinning the tires on a lift.

 

I'm good with the characteristics. I'm just trying to figure out what has broken or worn out to cause the LSD to now lock up properly and act like an "open diff". The shop said is is common for the Evo 9's to do this but I'm having a rough time finding anything on the net.

 

+1

When you spin the tires alone, the opposite tire will spin in the opposite direction. This is because of the spider gears. When my diff was still apart, I was messing with the spider gears. I put just the gears together and when I turn one side, the other side turns opposite. Turning the wheel while the car's in the air isn't really a good way to know if you have an LSD or not. All Evos come with LSDs.

 

The mechanic had the car in first gear so all the tires were spinning. He took the head of the hammer and applied pressure to one of the rear wheels. Whatever the result was it was different than the front and he said it's broken.

How can I test to see if the LSD is functioning properly? Have you ever heard of the rear LSD's being a weak spot on the 9's?

 

What exactly was he testing for? The plates were not arranged correctly from factory and the resulted in it being an "open diff". The plates did not grab correctly and the wheel that was slipping would always receive power rather than having equal power to both wheels. If you want to see broken, here:

The plate on the top is what it's supposed to look like and the 2 bottom plates have missing teeth. This is what made my car understeer like crazy while taking left hand turns because the car was in constant 3 wheel drive instead of all 4. If you want to check for this, easy. Drain the diff and see if metal shards and shavings come out. I know my oil was bright silver when I drained it...

I have never heard of the rear diff altogether being a weak spot. I don't know what mechanic you went to but it sounds like they're trying to get you into giving them a job so that you can pay them just to "replace" something and tell you it's fixed. As for testing, I don't know. Maybe drive on wheel on ice and the other on dry pavement and see if the wheel slipping slips a lot more than the other. Even then, it'll be hard because it's AWD.

 

I'll call the shop tomorrow and clarify what they were testing for. Maybe it was a cursory inspection to see if the car had a TRE/Shep/Weir aftermarket LSD. I asked them to identify any aftermarket parts they could. The USDM plate configuration on the rear LSD would explain why it responded differently from the front LSD when they did the test. Now, after looking at the inspection sheet they provided a "broken" rear LSD was NOT included. I enjoyed the dialogue! LOL

Seriously....thanks for taking the time to help me out! - Rick

 

if you want to fix the rear diff. do this https://www.evolutionm.net/forums/ev...y-factory.html

 

I've heard a lot of good things about both the TRE upgrade as well as the Weir performance upgrade as well. I'm debating on doing the upgrade on my car soon.

 

I am going to start with this and see how I like it.

If the JDM rearranging isn't aggressive enough for me I plan on doing one of these as well. I was leaning towards TRE but the downtime...and cost....has me leaning towards Weir.

 

This is true of geared or helical lsd's that some evo's came with up front, because with the wheels off the ground it acts the same as an open diff and the wheels spin opposite. If a clutch type lsd has a high preload they will spin together(even if spun by hand), with little to no preload then only one might spin or they may spin separately(different speeds).

My car has clutch type front and back so both front and back will spin together. One set has little preload so it doesn't immediately spin with the other as it takes a bit of a turn for it to "catch". The other set spins like they are locked together, and all 4 will end up spinning in the same direction.

 

short answer... TRE is the way to go. He does soo much more than just re-organize the plates.

Shot peening, HD bearing upgrades, sightglass window addition, new bearings, gear detailing, and proper ring and pinion alignment.

The MAX LOCK rear diff from TRE is worth every penny.

 

Here is what I'm reading on Weir's site, and I'm assuming they are talking about TRE in part of it:

"Our kit comes with 12 new plates which adds one more clutch per side gear within the LSD. This is the ONLY real aftermarket 12 plate kit that lets you keep the spring discs on each side of your LSD without having to machine the pressure rings. Without these spring discs, there is zero preload within the LSD. So, what do the "other guys" use in their LSD's? Well, they use O.E.M. parts and either remove the disc springs or machine the pressure rings so they can fit the extra plate into the stock LSD casing. Are they replacing all of your used plates with new ones? The answer is no, they are only adding one new plate to each side of your LSD. With our MAXGRIP kit your LSD will lock harder and firmer than you ever thought possible and still remain street friendly. The best part is you can install this kit on a Saturday in your garage and save the expense of shipping your diff and down time."

I'm curious what folks think about it...and the differences between the two. Can I expect a performance difference with TRE's gear detailing, shot peening, etc, or is it a durability factor or both?

 

Had to go outside, jack the car up, and test this for myself. Yes, you are right. The wheels spin in the same direction. I thought since there was no load (like no power going to the driveshaft from the front), it would spin in opposite direction. Guess I was wrong.

One problem. Not many of us can afford it. Yes, $465 is a deal but you're not including shipping to and from and the sight glass is an extra $85. Weir's 12 plate is the poor mans 12 plate. 8 plate mod is the poor mans LSD.