EVO 8 DIFF fitted & working

[Louis]

The EVO 8 rear diff, or one from an EVO 7 onwards, will bolt straight in.


Remove your VR4 rear diff as follows.
Pull out the rear drive shafts from the diff (I am sure this is covered elsewhere on the forum) and remove the AYC pipes, let the ayc fluid drain out.
The brackets at the front on either side 3 bolts 17mm on each, and 4 big bolts 22mm. Also 4 12mm bolts which hold the propshaft to the flange on the diff.
that’s it take out the DIFF

The only thing I had to change was the propshaft flange as the Evo one was thicker and would not have fitted so well, so remove the VR4 diff prop flange and remove the EVO8 prop flange and swap them over, this is one big bolt in the middle.
Then fit the EVO 8 diff.

The only other thing, is I replaced the diff oil with amsoil severe gear oil, all good. I also replaced the diff ayc fluid, NOT the reservoir and bleed nipples part. I did all this before I fitted the EVO 8 diff. What I noticed is:
WHEN fitted the filler for the ayc, up high at the back of the diff is in a slightly higher position on the EVO 8 diff, so you will not be able to remove the bolt to re fill the diff when the diff is in place as the bolt will hit the rear diff bracket before the bolt of clear.
When changing the fluid you will probably have to remove the rear diff carrier bolts (2 of them) to allow the diff to drop, and then you will be able to access the filler bolt.

The rear diff ratio:
I could not find a definite answer to what the ratio was,
so this is now a definite answer as I stripped both diffs and did the calculations.

VR4 1998 rear diff crown wheel teeth = 53
VR4 1998 rear diff pinion teeth = 16.
Divide the crown wheel number by the pinion number to give the ratio.
53 / 16 = 3.3125

The EVO 8 rear diff crown wheel teeth = 43
The EVO 8 rear diff pinion teeth = 13.
Divide the crown wheel number by the pinion number to give the ratio.
43 / 13 = 3.3077

The difference in the ratios is 0.00480

After fitting the diff we raised the car on 4 axle stands and started it up and put it in drive. The reason being, that if the front diff and the rear diff were moving at different speeds this would have been shown up by the abs sensors.
This did not happen, there wer no warning lights on the dash nothing and there still haven’t been.

The EVO8 diff having less teeth means the teeth are much bigger and more substantial, as well as the gearset being different to our (or older evo ) diff. The VR4 originally has a bevel gearset, the new diff (EVO 7 onwards) has a Planetary gearset.

Which actually looks like an LSD, whereas the original looks like a standard diff (non LSD) with ayc gears, the newer diff looks like an LSD (limited slip diff) with the addition of ayc.


The diff is fitted and the car is running fine, I will update with any news as I go on.

I also bled the AYC diff myself, see my other article.

[Louis]

The advantage of fitting a later diff, and what are the differences:

The later diff with Super Active Yaw Control, is 30% stronger,
People bought evos, made some minor changes like air intake and exhaust and boost controller, took them on track and blew the diffs.This resulted in lots of complaints. So Mitsy beefed up the diffs.
“AYC has come under criticism in some quarters for not transferring enough torque to match the increased power outputs of the latest Evolution models when shod with high-grip tires and driven on race circuit or other high-friction surfaces. Responding to this, MMC developed and now introduces Super AYC after carefully calculating torque transfer requirements under simulated race conditions. Switching from the use of a bevel gear to a planetary gear differential, the new unit is able to transfer twice the torque of the current AYC.”

This was a mechanical change not an ecu change, it is not an elecronic change.
The evo 8 diff has a planatery gearset, This is different to the old bevel gearset that we and the older EVO’s have.
It is the diff itself that is mechanically capable of transfering 30% more power.
What the ecu does is control the AYC pump and the solenoids at the pump (3, the ayc pump relay, the proportioning valve and the direction control valve, this last one diverts the ayc fluid to either the left clutch pack or the right clutch pack), there is no ecu control of the diff directly (no wires going to it).
The VR4 AYC ecu will be fine, the later evo ayc ecu controls the acd (Active Centre Diff found on later EVO’s)as well as the rear ayc, but we do not require this. Our AYC will do exactly what it is meant to do and will work the exact same way with the later model diff.

The weight of the Super AYC unit has been reduced by 800 grams by switching from steel to aluminum for the clutch case and by reviewing the metal clutch disc gauge.

The EVO8 Diff that I have is the same ratio as the VR4 diff, I worked it out at about 3.3.The diffs are a different size, but the ratios are the same.
This is not to be confused with final drive ratio which is done at the transfer box and is different for different models of evo and legnum etc. There are many gear sets for models and types of evo.

How to check if both diffs are the same ratio, What to do is open the inspection cover on both diffs, look at the crown wheel and pinion. Mark the crown wheel and pinion with a bit of tipex, and count the teeth, till you reach the tipex again, it both diffs have the same number of teeth, they are the same.

The following is information that I have collected from various internet sites, so apologies for copying and pasting and thanks for making the info available

[Louis]

useful links

http://www.lancerregister.com/faq_g04.php

http://www.edmunds.com/insideline/do...deoId=20033334

[Louis]

Feel free to ask questions, cheers

[Kieran]

That's bloody brilliant information there Louis - thankyou very much for sharing it!

Have yourself a couple of rep points!

[Nutter_John]

I Agree have some rep from me as well

[Louis]

Should have mentioned the diff I have is from an EVO 8 FQ 320, but all the EVO diffs are interchangable. The good ones are the EVO 7 onwards.

[valmes]

The rear diff ratio:
I could not find a definite answer to what the ratio was,
so this is now a definite answer as I stripped both diffs and did the calculations.

VR4 1998 rear diff crown wheel teeth = 53
VR4 1998 rear diff pinion teeth = 16.
Divide the crown wheel number by the pinion number to give the ratio.
53 / 16 = 3.3125

The EVO 8 rear diff crown wheel teeth = 43
The EVO 8 rear diff pinion teeth = 13.
Divide the crown wheel number by the pinion number to give the ratio.
43 / 13 = 3.3077

The difference in the ratios is 0.00480

That's a bit of difference actually... I mean Front and Rear are not locked so you will be able to drive the car, but I would imagine it will take a toll somewhere else. I hope I am wrong on this one...

[bradc]

It is 0.145%, I doubt that makes a difference, especially when if you have a brand new 235/45/17 tyre it has a circumference of 2020.30mm, if you get 1mm of uneven treadwear, thats 2014.02mm, or 0.312%, which is about twice as much as the difference in the diff.

Basically isn't nothing to worry about, but if you had a pair of tyres with a little bit more tread, you'd put them onto the back of the car, and not the front

BTW, great result Louis, and great article. Can you feel any difference in handling at this stage? I might be on the lookout for an EVO7-9 diff now

[Louis]

hi valmes,
IU was very concerned about the ratios being out, but like I said the difference is 0.004, which isn't a lot The basic check i did, was to raise all 4 wheels, start the car, put the car in drive and see if the abs sensors picked up if the wheels were moving at different speeds!. We laft the car running up there for about 10 minutes, and then bled the AYC with the wheels off the ground and in drive. So for a good 15 minutes the wheels were turning, and No abs lights came on. So even if the diffs were slightly out, the wheels would have started to go out of sync at some point.
I also did the maths on how much it actually worked out at, (like bradc has done) and I don't think it is too much.
Again, I will keep you all updated going to do some testing in the dry today, and then in the wet (probably soon as I am in Scotland!). As I am thinking if one diff was turning noticibly faster or slower than the other, this would induce a slide on a wet corner!.
If you don't try you don't find out!.
Like I said I will keep you all posted.

PS Brad, I syuck a link in your "evo gearset problem post", that may be useful.

[Wodjno]

Excellent News Louis

Great Info

I started to take out my Rear Diff last night(as i only found my locking wheel nut keys, last night)

From the info i had gained from Numerous sources, i to had come to the conclusion that the difference in ratios between EVO8 diff and our own was negligible..

I be continuing with it tomorrow and hopefully get it up and running, if not it will be Thurs or Fri..

I've had the Bl**dy Diff for 2 months now So bout time i got it in

Again, Great Work..

Does there fell any difference in cornering or have you not pushed the vehicle yet..


Rep coming your way Sir And well deserved to..

[bradc]

Louis, already replied to the evo one

I wouldn't worry about the ratio difference at all, I've managed to find one here in NZ for $1150, how much did you guys pay for yours?

[Wodjno]

Louis, already replied to the evo one

I wouldn't worry about the ratio difference at all, I've managed to find one here in NZ for $1150, how much did you guys pay for yours?

They normally sell for £500 to £800 for the S-AYC in the UK

[bradc]

I'll get him to put it up for $1k cash

[Wodjno]

I'll get him to put it up for $1k cash

And Some

[Louis]

Hi, Been out all day, put about 150 miles on with no problems. A lot of time spent in big open car parks, on full lock and bigger circles, accelerating fast forwards and backwards. Also did a lot of miles on twisty country roads, and a lot of time on some smooth surface big quiet roundabouts.
Now,
I am on a new set of 4 new tyres, so grip is good anyway (lovely dry day today and warm). But even not counting the new tyres, I feel there is a positive difference, much much harder to loose the back end, it does seem to stick to the road a lot better.
There is also the knowledge of what is there now (the new diff), which after looking inside it before fitting, it is just SO much tougher looking internaly.
It does feel good though, a new lease of life.
I'm on a real "what a car" vibe just now.

PS. I am lowered, on stiffer, D2 coilovers, so the stance is much lower and stiffer, with no roll on corners etc, (perfectly level and stable anyway) and I am on Brembos from an evo also, so stopping is much better, so the cornering is great anyway before fitting the diff, But a definite improvement with the diff, I need to try it in the wet to get more info, but I will keep puting up info, cheers for all the points and positive feedback, cheers Louis

[bradc]

ok you've sold me! S-AYC coming my way!

[Louis]

If you can find one, You could go for a diff from an evo RS, it is a limited slip diff with NO AYC, in a cast iron case, (weighty but bullet proof), you would need other bits also.
But.
The reason the EVO 7 and onwards diffs are more expensive, is because they are harder to find, as many track day racers and rally teams feel that the later model AYC diff is up to the job.
So there are not so many people taking them out to replace them with aftermarket ones.
You can also fit a cusco 1.5 way diff into the rear diff casing.
As for the diff, I feel it is worth doing.

[bradc]

Already found one for $1150

[Gly]

doz the S-ayc actually work?
or doz it just act like our normal ayc?