To me, I sense a hint of understeer with the RS's helical front diff under power. It does feel a little tighter and is able to hold its line better than an open front diff Evo. It feels like the front end is biting more than you would have with the open diff.

The car is set up for you to pitch it into the corner by lifting the throttle, trailbraking, or a little of both. Then you aim it where you want it to go, and power down. It'll tighten up the line and propel you towards the direction of the front wheels.

I feel that you can do this with the open diff, but it will be slightly harder to bring the front end back into line.

I think that the front diff enables you to tighten the line more quickly, and so you can be more confident and induce a little more oversteer than you would otherwise.

Nonetheless, I don't think that most people will be able to notice the difference. It's something that you can't explore at the legal speed limit. Any Evo is rock solid at speed.

 

..

 

How difficult would it be to install the RS front diff on a stock 03 EVO (GSR or whatever)?
Based on the couple of threads I have read you only have to touch the front diff and deactive the ABS. Is the accurate?

Are there any other options?

 

Also necessary to ensure that BOTH front and rear gear-ratios (crown-wheels & pinions) are the same. The Evo 6 Workshop Manual says that the ratios are 4.875 (78/16 teeth) RS "close-ratio" or 4.529 (77/17 teeth) GSR (standard box). It might become necessary to swap front crown-wheel & pinion with original GSR gears, to ensure a correct match if you also have standard GSR rear diff gearing.

Come to think of it, maybe it's best just to swap the RS LSD (+ GSR crown-wheel) to the GSR transfer case & re-install. Maybe you can then avoid "shimming" & set-up issues that MAY otherwise arise when also swapping the pinion as well.

Local users say that the "close-ratio" RS box & diffs TOGETHER are no fun for normal street use, (lower milage too.) It may be better to go with wider ratio GSR box + 4.529 gears + RS front diff for the street. (No personal experience here yet.)

Final point: It seems that early front LSDs (Evo 4-6, maybe later?) suffer from bolt failure. Find the FAQ & FIX here: http://www.lancerregister.com/faq_f05.php
I think I'll post this on main forum too. Maybe a 'sticky' will help?

 

Perhaps some are alot better then others. Like I said, I haven't driven an RS so I can't really say.

At least the front end is a little lighter without one