Great point about the reliability, and it's exactly why i was considering it. just wanted to make sure it's applicable - ie, built motor = reliability (typically) but you don't get ur motor built when u're only making 300whp, kind of thing.

After hearing Evolutionary's results, I think this is definitely a must do mod for anyone who's driving their car in more serious environments - i'll add the mod to the first post

 

I came back from my first track event at Thunderhill with the TRE diff. My evo was VERY neutral and am happy with its setup, I dont have any complaints about turn in understeer, but I do think I have outgrown my robispec spring setup at this point. Like I said before, if you can get a hold of TRE you should definately consider this as one of your first mods.

 

Sounds awesome - looking forward to a ton of reviews from people as the weather starts to warm up - correct me if I'm wrong but you also have the Gruppe-S ACD reflash correct? Can you comment on any individual contribution from it? Someone asked me the other day but I had a hard time giving a very tangible response - though it does make a pretty good difference, no doubt about that.

Overall I think with this thread plus the TRE thread and the others I feel like we've reached a good population of ct9a drivers who track their cars competitively, which makes me happy!

you mentioned how you didn't have any complaints about turn in understeer- are you saying that the rear diff upgrade neither improved nor reduced the turn in? i'm actually looking for ways at the moment to really ramp up the turn in ability of the car - after experiencing it in the X it's the next area of the car I want to take a look at

 

The rear diff upgrade and the Gruppe-S acd reflash has really made an improvement to improve turn in and reduce overall understeer. I should have made that more clear,sorry. Compared to stock it has been a much improved setup. My setup is 18x9 RCt4 enkeis w/ 255/35/18 star specs, Robispec springs w/oem kybs, Gruppe-S race flash, TRE max lock rear diff 1.5way.

Before the diff upgrade, I was also going through front tires alot more. Part of that was over driving the car, but also alot of it was just the turn in understeer I was trying to dial out. I also had that issue when I had gotten the ACD race flash with binding during tight autox sections that seemed to be eliminated when I had the diff installed. I was curious how the race flash and the rear diff would act at a road course and was very pleased this weekend with it. No binding issue found anymore, either at the autox or the road course. I dont have anything to compare running on a track with only the flash or diff so I cant comment on that aspect. WITH the flash and rear diff you will have excellent turn in capabiities though. You can also dial in a little bit more aggressive rear diff using redline 75w140NS with no friction modifiers. You'll get a few odd looks as you turn back into the paddock with the rear end crunching like its gonna fall apart though.haha. I think Im only running that fluid during events from now on, otherwise the redline 75w90 has the friction modifiers in it and is quieter for dd.

With the rear diff you will rotate the car much easier and put less strain on the front tires trying to push you through the turns. I think with R comp tires or a good set of coilovers you will see a larger difference with the different race flash settings as well. I have such a mild setup that I couldnt see a huge difference between the 3 different race flash settings. There was a difference but like I said, with my setup it wasnt super obvious like It is at an autox.

 

^ damn it i should have gotten a ride along with you..i can't wait to try my Diff out on track (gets here tomorrow)

I was the silver 9 car 0 in open.......didn't really do very well until the 2nd day after stopped raining..with nt01's my car just pushes and when i put the star spec's on i was getting off throttle over steer around 2 and power over steer coming out of 15 which made the car so much easier to drive and faster.

I'm hoping I can get that same kind of thing with the diff..except on nt01's

2:09 was my best time. with a damp track

 

Whats your toe setting? If I run 0 toe I get terrible turn in, but if I add 1/2 turn toe out on each front wheel while changing tires the turn in is amazing. You don't have to worry about wear on auto-x cause you spend all your time turn, but I don't know how it will effect high speed stability on track since I spend all my time dodging cones

Also, with a front torsen diff its extremely important to not turn off throttle. You don't need to be accelerating but you need enough throttle so you aren't engine braking. If not the front diff has a bit of lockup and it causes more understeer. This of course is better anyways since you're already starting to pre-load the turbo through the turn ready for corner exit.

I dont see how the rear diff will effect turn in personally. I feel no difference between my talon (viscous) and Evo (clutch) on turn in. Corner exit is a whole different story though.

 

just got a picture from my room mate of a box that arrived at the door with my name on it...I wonder what it could be

 

I was gonna rent a timer but I wasnt happy with my lines on a few turns, so not worth it for me. I will try to go back out in May with a few other goodies on the evo. Ill see ya out there hopefully.

 

I did it myseLf seeing as the plates are installed wrong from the factory for the price of a service manual silicone and oil for it with a little knowledge and a little time you can do what they charge 300+ for in your own garage for about 15

 

WOW! If it's that easy you should go into business and only charge $250 to do it! You would make a killing!

It's true that moving the plates around can improve torque transfer. Maybe that's all certain shops do for $350 as you stated - don't know what other shops do.

As for TRE - for a whopping $450 you get:
- magnaflux inspection of differential carrier housing and bearing caps
- magnaflux inspection of ring & pinion and spider gearset
- NEW friction/drive plates (12 plate is standard)
- shot peening of ring & pinion
- shot peening of spider gearset
- new pinion & carrier bearings
- new shim kit for preload of both pinion shaft and carrier housing
- adjustment of the spider gearset backlash
- adjustment of ring & pinion for high torque applications
- new pinion shaft and axles shaft oil seals
- a heavy coat of satin black paint so it looks like new again
- new fill plug
- new drain plug
- modified side sheaves
- new carrier cap bolts
- new rear cover bolts
- new rear cover with oil sight glass is optional. $85.
- new HD side cover is optional. $265.
- new TRE spool is optional.
- new HD pinion spacer is optional.

There is also other work done that is not public info. Hmmm . . . sounds like a good deal for the price to me. . . but we each get to choose how to spend our time/$$.

 

my TRE diff is in...can't wait to test it out.

 

TRE rear has arrived. here she is.

 

^ Teh hotness!

l8r)

 

I have assembled a few diffs and just like engine building, its all in the details. Someone who really has experience building these, Like TRE, will know what specs and measurements actually work best for high performance applications. There really is alot more to this than just service manual rebuilding-- which is fine if all you want is something similar to what oem recommends. Remember that not always what oem recommends is necessarily optimal for performance. Its all in the details and his experiences with modifying what he has seen be a weak point--- you probably wont see that in any service manual.

 

I spent the day at TRE. I have been there 4 times. Jon built my diff today (looks like the pics above) He is always thinking on how to make our EVO's work and perform better. Jon has some more parts he is working on like the side cover that will be better then the factory stuff. He is in the man when it comes to the driveline!