The Cusco 40/60 that is being referred to is the center diff and that is located in the transmission and it will bias the torque split between front and rear differentials.

Having more bias towards the rear of the car is good for making the EVO finish the turn while having your boot on the throttle but this only works if the rear inside tire doesn't spin into smoke because the rear diff can't provide the necessary lock-up.

If the rear diff can provide enough lock-up the car will enjoy the advantage of better acceleration while exiting out of a turn. Also, the driver can steer the car out of the turn with throttle thus unwinding the steering wheel sooner and anytime that you can use the throttle more and steering less the car will be quicker around the track.

Now understand that too much lock-up can be just as bad as having the suspension set up wrong and based off the feedback from the test group it sounds like the rear diff upgrade is working properly, providing the ideal amount of lock-up without making the car squirrelly.

 

So, let me see if I understand:

A perfect combo would be: A properly built TRE tranny with the cusco 60/40, a TRE re-manned t-case with ralliart or quaife front diff. and a TRE re-manned rear diff upgrade with adequate locking

This would then allow to opt for a softer rear suspension perhaps as the car will rotate more as-is without the need for a big rear bar or stiff rear springs...



Good to know I am 2/3rd's of the way there, Jon! Thanks for all your help and great customer service!

 

Jon - And for those who want max lock - you do offer a 2 way and a 1.5 as well, correct? I know you recommended the 1 way for me and thats what I went with.

I figured readers can see that you offer more than just 1 option based on their needs and type or racing....

 

At least from an autox standpoint it does not allow for a softer rear suspension. The effects of the 40/60 and rear diff are only felt on acceleration and do NOT affect transitions or steady state.

John

 

For those who want max lock-up I'm working on a 16 friction plate rear diff but this would be best for those who are in the loose slippery stuff (snow, mud or ice). I'm guessing that it'll have too much lock-up for pavement and the car might become a bit squirrelly after the apex when the throttle is mashed.

1-way type is only providing lock-up when accelerating. Both neutral throttle and decel will act just like an open differential.

1.5-way offers works just like the 1-way except it will provide a little bit of lock-up on decel. Neutral throttle will act like an open differential.

2-way will offer lock-up during both accelerating and decel but to a lesser degree being that the ramps on the side sheaves mustn't have to much angle of the backlash will beat up the cross shaft and ramp profiles. Neutral throttle will act like an open differential.

From what I've gathered, the pro's like a 1-way diff being that they want to have the car free of influence during decel so it won't upset the suspension or turn-in characteristics while rookies may like the forgivingness of slower turning that a 1.5 way offers.

2-way is going to provide lock-up in both directions and this can be an advantage when the driver wishes for the rear of the car to get loose and rotate during well timed downshifts that are often found in rally or Tokyo drift type driving. Again, I'm not the guru race car driver and would like to hear other people's take on what works for them.

Jon

 

Thanks for listing this out clearly, Jon

PS - PM or email me back as to the details on my TC you are finishing up on. I tried calling, but no answer. I understand you are busy and probably have a bunch of stuff to get done and I don't want to chat your ear off like last time

 

Wanted to provide some additional feedback on the rear diff upgrade: simply put ... IT WORKS! Had the chance to slide the car around a bit last week, and the car barely pushed (if at all) under power coming out of hard corners. This is on a stock '03 suspension with only minor upgrades (rear trailing arm bushing and rear strut tower brace). I'm very happy. IMO one of the better, lower cost upgrades I've put on my car.

On a separate note, the AMS solid rear diff mount is nice, but probably too noisy for prolonged street use...

l8r)

 

Thanks, Ludi. I am exicted. My rear diff. is here. My TC is on the way back. I wish Devo had the lightweight driveshaft ready as well so I could bolt on the stuff. Damn CF one costs a metric azzton pounds, else I would just get that!

 

I finally had the chance to put the rear diff to the test this past weekend, and I was impressed. I had several changes made over the off-season, so it's tough to make a side-by-side comparison between regular rear diff and TRE rear diff, but from my experience the TRE rear diff was well worth it.

TRE did my rear diff, along with installing a front LSD in my t-case (as well as a Stage 2 tranny rebuild). I took the Evo to an autocross at Devens, MA this past weekend, and I and Point&Shoot, who co-drove with me, put it thru its paces.

The car handled very well, with a HUGE difference in the amount of understeer it exhibited. While I'm sure the front LSD helps eliminate some of it, teaming it with the TRE rear diff made the Evo become a much better balanced vehicle. It wasn't overly tail-happy, but it certainly rotated when needed. The grip and balance was even more impressive when you consider this was all on year-old R compounds and mid-50s temps....

 

Hey guys,

Thanks for letting me work on your stuff.

 

Thanks for doing such great work on our stuff!!!

 

EJ and Ludi: just to clarify, are you guys on stock center diffs or have those been upgraded as well? I just want to make sure I dont need a new center as well before I install the rear diff.

To the collective: would using the 1.5 or 2 way diff be good to also induce rotation on corner entry? Or would this be too much upsetting of the car and be less effective than setting up early for the turn or using trail braking?

 

With the exception of the TRE rear diff and an Exedy Twin Metallic clutch, I am on a stock '03 drive train (open front diff, ugh, and stock center diff).

l8r)

 

Neither ejevo nor I have the center diff, and we both saw a great improvement in corner exit and attitude control in corners, with the TRE re-build. I should point out though that we both have the OEM helical front diff (the Evo 9 part). That makes a big difference in reducing front wheelspin on corner exit, allowing you to get more power down more quickly.

Mike

 

I just installed the evo9 front diff (sourced from TRE, and very quickly at that) and it was definitely a noticable difference, which is all the more reason I like the idea of the rear diff rebuild as well. And with all that Ive put into upgrades this year, after a new set of r-comps, this will be all I can afford.