Strengthening the diff, any options, possibilities, recommendations?

[Madhav]

After hearing of a few members experiences, I figure I should be well informed ahead of time as to what my options are because it seems our AYC diffs are not much good for power figures above 450hp. Correct??

Has anyone got any experience or done any research? What are our options?

I know that the super AYC fits well and is supposedly a little stronger? Question is, how much stronger?? Strong enough for 300kw atw clutch dumps?

I found a evo 8 RS diff centre for $700, these are supposed to be really strong, anyone know if they can fit into our VR4 casing?

 

[pu-11-me]

Cusco Type-MZ LSD.... Also for EVO's

Should be able to pick one up through RHD or Nengun. Just look for an EVO 6 one...

 

[Madhav]

Just found a very useful thread on club vr4 (search really is your friend)

It appears that the destruction of the AYC diffs is caused by flexing in the alloy case under heavy torque loads (i.e. 300kw atw clutch dumps) and replacing the diff centre helps, but doesn't really solve the weak casing problem.

The type V diffs have a cast iron casing, and are therefore supposedly less prone to flexing, but then I want my ayc, so what to do... ? Is it possible to swap the internals of a super AYC into a cast iron case?

 

[mookers]

Is it possible to add stiffeners to the stock casing? Or get someone to fabricate a stronger case (would be $$$$$ I guess)? Or am I talking complete bollocks?

 

[pu-11-me]

The cuso is just the centre.... The Type-V diff is not an LSD either, its open. Optimally what you want is the cusco centre in a Type-V casing. Thats just my completely unbiased opinion

Ask Carsten (Gly) how strong the AYC diff centre's are.... He's replaced 3??? I think...

 

[Madhav]

The cuso is just the centre.... The Type-V diff is not an LSD either, its open. Optimally what you want is the cusco centre in a Type-V casing. Thats just my completely unbiased opinion

Ask Carsten (Gly) how strong the AYC diff centre's are.... He's replaced 3??? I think...

Yeah this would do, although would the ayc still function?

 

[pu-11-me]

Nah, but its hella fun when the diff locks

 

[bradc]

Carsten originally had one gear break apart, from memory it was the pinion, so he replaced that. He then had the crown and pinion break so he now has a new set in there.

Madhav's research is correct, basically the flex allows the gears to move a bit further apart than they should, which in turn destroys them.

The EVO 4 and VR-4 diff's both have a 16/53 tooth setup whereas EVO 5-9 are 13/43. The fewer gears are obviously bigger and stronger and on those the problem is greatly reduced. Once you go up to huge levels of power though you will still have problems. The best fix is to simply NOT launch at all and to perhaps limit power in first gear. Remember that in first gear your 600 or so NM of torque is being multiplied by 3.333, then 4.111. It is then reduced by 3.3125, then at the 16 tooth gear you have approx 2480nm of torque!

 

[Madhav]

Don't launch?? What fun is that!! But yeah point taken, until I sort out something stronger, at the very least a later model evo diff, no lauching at 5000rpm for me.

Brad did u mention somewhere that changing the gear ratios helps take the pressure off a bit also? How much did that set u back?

 

[Guest]

ive been told that...

the evo 7 and newer rear diffs are upto 30% stronger than that that of its predicessors
due to the gears being beefier (gear ratio change)
and and also of helical design rather than the older hemispherical

also you can shim the diff (sorry don't know if this is the correct term)
to remove the play before engagement (there is a lot of slop in a vr4 rear diff), this will prevent the gears slamming into each other at launch

 

[bradc]

As above Carsten, from EVO 5 upwards the ratio was different and in turn the gears are stronger. The AYC part of the diff is made much stronger in the SAYC's in the EVO 8 and 9, but the AYC part doesn't break that much anyway.

Madhav - I have a 2.928 1st gear and 1.950 2nd. Stock is 3.333 and 2.105. Therefore I'm putting 13.83% less torque through the diff in 1st gear than I otherwise would be with the stock ratios. You can buy all of the parts individually for the manual gearbox. You do have to buy 1st and 2nd as a pair though. I bought my entire gearset for a very cheap price from Ralliart. They don't have any more though.

 

[Madhav]

Ok good, so a later model super ayc diff in combination with those gear ratios mentioned above will give 40% more strength in first and second? Well this should theoretically solve the problem...

Question is where to buy those parts?

Diff should be easy enough, plenty of evo 8's wrecking around Oz and NZ, any ideas where to get the gearsets?

 

[unclepaulie]

http://www.evolutionoz.net/forums/index.php?showtopic=331

this thread is a detailed 'how to' on converting ayc to LSD (with pictures) (also show detailed views of ayc rear diffs, planetary gears, friction plates etc)

vehicle used is an evo 8 iirc

so maybe this same process could work in our VR4's; and BAM throw a 2way in the back

i dunno , hope it helps your quest madhav, results would be interesting

 

[ygoslo]

Nah, but its hella fun when the diff locks

Interested in how this behaves - do you get all the clunking and banging that usually comes with a mechanical diff or is it quiet? And have you noticed added understeer? Do you know if it is a 1 way, 1.5 or 2 way? Where do babies come from?

 

[mookers]

Interested in how this behaves - do you get all the clunking and banging that usually comes with a mechanical diff or is it quiet? And have you noticed added understeer? Do you know if it is a 1 way, 1.5 or 2 way? How is babby formed?

FTFY

 

[Madhav]

http://www.evolutionoz.net/forums/index.php?showtopic=331

this thread is a detailed 'how to' on converting ayc to LSD (with pictures) (also show detailed views of ayc rear diffs, planetary gears, friction plates etc)

vehicle used is an evo 8 iirc

so maybe this same process could work in our VR4's; and BAM throw a 2way in the back

i dunno , hope it helps your quest madhav, results would be interesting

Read the whole write up twice, basically the dude ditched the AYC bits completely and replaced the diff centre with a cusco LSD one. However later on in the thread there were some other comments similar to what I read on club VR4 about the casing not being up to the task. And they were saying it's just a matter of time till the crappy alloy casing dies...

Ideally, and I really wish someone knew the answer to this, if we could use the type V VR4 cast iron diff housing with the cusco centre it may solve the problem and cost less?

So the other option is, to sum it all up, is to use a RS style diff, and not an AYC diff. This is what the dudes in the Evos are doing.

Next question is where to get one? The USA, all Evo IX's had them, so there are plenty wrecking, and they go cheap so I hear.

Do they fit? Well they definitely fit the JDM evo's, the dude at meek fitted one with a weld or two, but I need to do more research whether they will fit ours... I mean Gowf got one to fit but he had to spend a fortune and source other bits to make it work...

Can someone who lives close to Meek possibly ask the dude what hope we have of fitting the LSD cusco to a type V casing, and/or also what hope there is of getting a RS diff to fit, and what parts we need.

 

[Guest]

Ideally, and I really wish someone knew the answer to this, if we could use the type V VR4 cast iron diff housing with the cusco centre it may solve the problem and cost less?

If you want to buy the Cusco centre, I'm more than happy to test it in my car

So the other option is, to sum it all up, is to use a RS style diff, and not an AYC diff. This is what the dudes in the Evos are doing.

Next question is where to get one? The USA, all Evo IX's had them, so there are plenty wrecking, and they go cheap so I hear.

You talking about the lsd that you get in the RS Evos? Because I thought they were very difficult to get a hold of, and cost a fortune as well.

Still, very interested in which way you decide to go.

 

[Madhav]

If you want to buy the Cusco centre, I'm more than happy to test it in my car



You talking about the lsd that you get in the RS Evos? Because I thought they were very difficult to get a hold of, and cost a fortune as well.

Still, very interested in which way you decide to go.

Thanks Stephen I'm hoping someone somewhere already knows!!

In regards to the RS diff, the JDM models are hard to get hold of, the USDM models are the ones I was referring to, they are plentiful and cheap.

 

[smohekey]

I've read a thread on an american forum about making a brace of some sort to strengthen the casing. From memory the brace took up some of the AYC clutch space, so it could only be used when the internals have been replaced by the cusco LSD or similar. I'm trying to find the thread now, without much luck.

 

[smohekey]

This isn't the thread I was looking for, but it does show the lengths some people will go to strengthen the rear diff casing!! Scroll to the last post on the first page.

http://www.lancerregister.com/showthread.php?t=268523