VR4 - Rear Diff upgrades

[bazeng]

Hi Guys.

I have a 4bolt rear VISCOUS LSD, and a 4bolt rear OPEN DIFF.

I want to upgrade to a mechanical LSD of some sort.

What are my options?

I have the opportunity to purchase an EVO3 rear mechanical factory DIFF and wanted to know if I could use the internals in the VR4 Diff.

Are the shafts compatible?
Are the shafts in the 4bolt equal length? or are they offset due to the 4ws?

Any info / pics appreciated.

Baz

 

One option is the KAAZ mechanical rear LSD for your 4-bolt viscous or open diff. Uses Evo 3 rear axles.
Mike R.

 

[curtis]

Baz the factory US 3 bolt and the 4bolt lsd from the dsms have different axles but the 4 bolt guts all fit in the 3 bolt 4ws rearend housing, I know because I did it to mine. The 4bolt lsd even had the machined surface for the 4ws to run off off. If I was to bet the mechanical diff you have will fit but the axles may be a different size. I know Paul had some problems with this build but can't remember everything that happened, but its probably in his big thread towards the front. I think he bought cusco units for his.

 

[Dialcaliper]

Only get the Evo 3 diff if its a complete rear end with axles (or at least the cups) or you'll be in for a serious headache.

Your options for mechanical rears (all will probably require getting rid of the 4WS unless you get really creative):

VR-4 RS Plate Type (1-way) - Bolt in except for the ratio - swap into any 3/4bolt pumpkin and switch the ring gear to your stock one. Use the axles that come with it (JDM). Stock 3 bolt or 4 bolt axles might work, but no guarantees. I believe Garfield has one up for sale as we speak.

Evo 3 (1-way) - similar but different. Swap the guts into a 3/4bolt pumpkin - use 4-bolt seals. You need to remove and use the Evo 3 tulips (stub axles), and a set of 4-bolt shafts up to the tripod bearing inserted into the Evo tulips making a kind of hybrid shaft. You can also use 3-bolt axles refitted with the larger 4-bolt tripod bearings.

Aftermarket (1, 1.5 or 2-way). Do everything described above for the Evo 3 Frankenstein axles, and transfer roller bearings and ring gear to the aftermarket unit.


Also, completely unconfirmed, but based in factory Tech manual information:

An Evo 8 mech diff might fit with some creativity. From studying the service manuals, it looks like the diff internals are the same from the Evo 3 to the Evo 6. and a similar diff carrier is used on the Evo 8. The evo 4-6 RS are definitely the same, and the Evo 4-5 technical information manual says, and I quote:

"Vehicles without the AYC system are fitted with a mechanical LSD. The LSD is basically the same as
that of the EVOLUTION-III."

The Evo 8 might have different stub axle splines (but the same tripod bearings?). Every single open, viscous and mechanical rear diff except for the later RS models appears to use 72mm OD, 35mm ID side roller bearings, and after 93, the same kind of axle stub tripod bearings...

The later RS model seems to have different side bearings (25mm ID, and the Evo 7 TIM mentions something about thinner walls for weight savings on the RS). You might have to source custom roller bearings to make it work, but it might be possible.

I've never had the chance to get my hands on an Evo 8 diff to try it out, so I can't confirm that it works. If you want more info, the Galant, DSM and Evo 4-9 service manuals are hosted on LilEvo's Site

My suspicion is that since the USDM Evo 8 was the only one to use a mechanical rear on non RS models, they simply grabbed the old standard mechanical diff guts from the Evo 3-6, popped some different gears in it, stuck it in a new housing and called it a day because it was cheaper than putting the RS version in every car. It would also make sense, since it was only a US thing, it would have been dumb to retool and build a diff from scratch or use the more expensive RS diff, when they entire point was to bring the price down (an AYC unit probably raises the price by several thousand dollars)

So, if anyone wants a project with a dubious chance of success, and has 2-3 different diffs lying around, it might be worth a shot...

 

[bazeng]

Dialcaliper,

Evo 3 (1-way) - similar but different. Swap the guts into a 3/4bolt pumpkin - use 4-bolt seals. You need to remove and use the Evo 3 tulips (stub axles), and a set of 4-bolt shafts up to the tripod bearing inserted into the Evo tulips making a kind of hybrid shaft. You can also use 3-bolt axles refitted with the larger 4-bolt tripod bearings.

If I have a 4bolt rear cradle/diff, do I still need to use the evo3 tulips?. Why can't I use the 4bolt shafts and 4bolt tulips?

 

[bazeng]

Curtis,

I read the whole thread lastnight.. It only shows a pic of the completed diff housing and the internal bits. But nothing about the process of bolting it on..

It was a long but good read.

 

[Dialcaliper]

Both the Evo 3 and pretty much every aftermarket unit (Kaaz, Cusco, etc) require the Evo 3 stub axles (tulips). It's the major reason you don't see more DSMs with aftermarket rear diffs, because they're hard to find unless you buy a whole Evo 3 diff assembly.

If the diff comes complete with axles for a good price, grab it.

I'm not sure which tulips the Evo 1-2 use, or the 4-6 RS models for that matter, but they might be the same?


Quoting bazeng:
Dialcaliper,

Evo 3 (1-way) - similar but different. Swap the guts into a 3/4bolt pumpkin - use 4-bolt seals. You need to remove and use the Evo 3 tulips (stub axles), and a set of 4-bolt shafts up to the tripod bearing inserted into the Evo tulips making a kind of hybrid shaft. You can also use 3-bolt axles refitted with the larger 4-bolt tripod bearings.

If I have a 4bolt rear cradle/diff, do I still need to use the evo3 tulips?. Why can't I use the 4bolt shafts and 4bolt tulips?

 

[RedTwo]

CE9A Evo 2 and 3 (standard fitment for both GSR and RS) run 1.5 way mechanical LSD units (MR166619). This is also the same part used in the non AYC CN9A Evo 4 and above (standard on RS and option for AYC GSR in most cases). E38A VR4 RS (3.909/4 bolt/face-lift) and CD9A RS both run the same 1 way mechanical LSD unit (MB664374). E39A VR4 (3.909/4 bolt/face-life) and CD9A GSR both run viscous LSDs (MB837570/MB837571)

All of these viscous LSDs run the same unequal axles/cups/tulips (MB837360 & MB837361 - Right and left respectively).
All of these mechanical LSDs use the same axles/cups/tulips (MB620942) for both the left and right. This is the exact same part numbers as the open diff axles/cups.

 

[bazeng]

Just to be sure we are on the right page, by stub axel are you referring to the part that goes into the diff or the part that goes into the hub?

(USA VS AUS LANGUAGE BARRIER)..

Remember, what we call driveshafts, you call axles. What you call tailshafts, we call driveshafts...

 

[bazeng]

So REDTWO, you are saying that with the OPEN DIFF 4bolt, the evo3 rear lsd should bolt right in without any need to play with axles??

 

[atc250r]

Open rear diff with welded spiders? That's only good for drag racing and kind of ghetto but domestic guys have been doing it forever here in the U.S.

John

 

[H05TYL]

Quoting RedTwo:
CE9A Evo 2 and 3 (standard fitment for both GSR and RS) run 1.5 way mechanical LSD units (MR166619). This is also the same part used in the non AYC CN9A Evo 4 and above (standard on RS and option for AYC GSR in most cases). E38A VR4 RS (3.909/4 bolt/face-lift) and CD9A RS both run the same 1 way mechanical LSD unit (MB664374). E39A VR4 (3.909/4 bolt/face-life) and CD9A GSR both run viscous LSDs (MB837570/MB837571)

All of these viscous LSDs run the same unequal axles/cups/tulips (MB837360 & MB837361 - Right and left respectively).
All of these mechanical LSDs use the same axles/cups/tulips (MB620942) for both the left and right. This is the exact same part numbers as the open diff axles/cups.



Very helpful that!

Would you happen to have the part number for the cups/tulips for an early E38A VR4 RS 3.545/3-bolt/pre-facelift mechanical LSD?

 

[RedTwo]

Yep, you shouldn't need to dick around with axles at all - the axle seals in the diff are identical (3 bolt: MB393932, replaced by MD707184. 4 Bolt: MD707184). Put a frost plug in the 4WS pump hole and retain your current pinion and crown wheel, swap over all the other evo bits and it should be good to go (some new shims would be a good idea too.)

3 Bolt Axles/cups/diff side CVs
E38A RS 3.545 (Mechanical) MB526960
E39A 3.545 (Open) MB526960
E39A 3.545 (Viscous) MB526964 & MB526965

 

[Dialcaliper]

Interesting info. Is it true then that on the JDM cars, the mech diff and open diffs use the same tulips? Also, are the tulips for the E38A/CD9A 1-way the same as the CE9A 1.5-way? If so, that means pretty much any JDM non-viscous car would be a source for the "Evo3" style tulips?

The reason I ask is that USDM VR-4's and Eclipses do not use the same tulips as the "JDM" cars. The splines on our stock open diffs are the same as the viscous diffs, except without the unequal lengths. Same with the 4-bolt diffs found on our 93+ eclipses. None are compatible with the JDM mechanical diffs (wrong spline count I believe)

If the above info is true, then for a NZ car with an open diff, you could simply drop in a Kaaz or Cusco unit? Or do all of your cars come stock with viscous units?

 

[bazeng]

OK,

I've recieved some KAAZ parts list and have noticed that their rear LSD's required some mitsubishi parts only if you have a viscous or open diff. The mechanical lsd rear evo3 diffs do not require any parts from mitsu.
(NOTE: EVO1-2-3/ ECLIPSE / AKA VR4 as KAAZ do not list the VR4, share the same LSD part numbers front and rear )

So, eclipse (aka vr4) come in open and viscous options. They require part number MB620942 to use with the KAAZ REAR LSD.

As for EVO 1-2-3, they come in open, viscous, mech lsd options. The open and viscous require the same part number as above. The mech LSD does not require that part mumber.

I'm getting an update from a friend from MITSU on what that part number actually is. I believe it may be the cup you guys are talking about.

Will let you know when I find out.

 

[Dialcaliper]

MB620942 is the P/N for the tulips/stub axles/tripod housings (whatever you want to call them) that match the splines of the Evo 2/3 mechanical insert. The reason it is called out is that KAAZ only makes one rear diff insert to fit the entire line of VR4/DSM/Evo RS's (at least up to the Evo6). To make the Kaaz work with USDM VR4's or DSM's, you need the Evo tulips.

I think part of the problem and expense in getting the right tulips from Mitsu is that that part number might actually be the entire axle, not just the tulips (which means buying 2 complete axles = $$$)

It kind of suggests to me that the VR4 RS mechanical rear (same as Evo I) may use the same tulips - It would definitely explain why units lifted from Evo 3 axles mysteriously fit perfectly with 4-bolt tripod CV joints, especially when you consider that the Evo 3 has a different track width and longer CV shafts (not to mention completely different hubs).

 

[bazeng]

I just recieved a message for that part number and you are correct, it is the tulip and shaft. Cost is about $650.00 AUD.

Luckily I can get my hands on a used one for $165.00 dollars, and the rear mechanical evo3 diff for about $400.00.

Hopefully it will be worth the expense and effort over the viscous unit.

Thanks for the help guys.

Information appreciated.

 

[gtluke]

I have a set of rear axles from an EVO 1 sitting in my office.
Does that help anyone?

 

[vr4play]

I am using an Evo 9 rear diff and rear inner axle joints. Bolts right into our rear end housing no mods. Seems to work pretty good. Much better than the viscous. Got it from a wrecked car. If you could find axles from a newer evo the inner joints should work with any of the mechanical diffs incl. the Kaaz. You do have to use 4 bolt axles.

 

[eviLntt]

^^^^ Do you have the 4WS removed?