Not sure I'm doing this test the right way, need confirmation to be sure I don't need a new diff/transfer case.

I've got the car jacked up. all four wheels off the ground.

Turn one of the rear wheels (RH rear) manually and the opposite wheel (LH rear) spins in the opposite direction?!?! This is not good right?

Go turn one front wheel (LH front) and the rears both spin in the same direction, but slower and not consistently - as in initially they spin at the same speed but it seems to "fade" and the difference in speed front to rear becomes more obvious. Turning the front right achieves the same result - slower and inconsistent.

Tried the same test on the rear wheels again with the front wheels chocked - front wheels cannot turn - same results; turning one rear wheel causes the opposite side rear wheel to turn in the opposite direction.

Blown diff? Blown transfer case?! Both transfer and rear diff blown?!

I was actually under there to replace my transfer and diff oil. Rear diff oil was like new.... haven't gone near the transfer as I don't have the tools to get any oil back in there.

UPDATE

I think I'm doing the test incorrectly - need to disconnect the drive shaft... NOT in any hurry to do that. As for the transfer... I'm still paranoid

wtf.. so does the car drive fine or what? dont spin the wheels with ur hand drive the bloody thing LOL

From memory, when I was getting the 380 brakes put on, spinning one of the rear wheels causes the other rear wheel to spin in the same direction as well as one of the front wheels. The other front wheel spins in opposite direction. Exactly which wheel spun which direction, I can't remember.

wtf.. so does the car drive fine or what? dont spin the wheels with ur hand drive the bloody thing LOL

er... LOL?

Drives fine... I guess? I cant remember the last time I was in a position to test the LSD's were functioning.

I think I might be panicking over nothing maybe.

why does it matter if theyre broken if the car drives the same? question answered.!

why does it matter if theyre broken if the car drives the same? question answered.!

Ah man, just because? If you pay for a bic Mac and it arrives without the meat you'd want that damn beef am I right?

This is exactly WAD (working as designed). You don't have a problem. The behaviour of the rear diff is the same on a 2WD non LSD except the slip is less limited :)

This is exactly WAD (working as designed). You don't have a problem. The behaviour of the rear diff is the same on a 2WD non LSD except the slip is less limited :)

This makes me feel somewhat better. I figured out I had done the test incorrectly, but some part of my brain wasn't completely convinced. Like I expected more.

While all of this was going on I did a few searches on the forum but still nothing to really convince me.

From memory, when I was getting the 380 brakes put on, spinning one of the rear wheels causes the other rear wheel to spin in the same direction as well as one of the front wheels. The other front wheel spins in opposite direction. Exactly which wheel spun which direction, I can't remember.

The car is off the stands now, I can't go repeat my tests. But, I think the only way I could achieve this (three wheels turning) was to manually turn the drive shaft. But, I can't remember which way each rear wheel was turning? Damn memory. Pretty sure I had three turning in the same direction? Drivers side front was stationary.... at least I remembered something. :/

The correct memory will return to me at around 3am tomorrow morning.

Is fine, the drag of the tail shaft and trans case causes this, your rear diff is fine by the fact when driven by the tailshaft both spin same way

Rear diff is the only LSD

When you do the trans case call me first so I can tell you how to do it properly

wtf.. so does the car drive fine or what? dont spin the wheels with ur hand drive the bloody thing LOL

And Hayden, there is no law that states you need to comment on every thread, your comment was useless

Is fine, the drag of the tail shaft and trans case causes this, your rear diff is fine by the fact when driven by the tailshaft both spin same way

Rear diff is the only LSD

When you do the trans case call me first so I can tell you how to do it properly

Groovy, thanks Mal.

Rear diff' oil change = easy.
Transfer case oil change = gonna need a pump of some description.

I had the car with all four wheels up off the ground and as level as I could get it with chassis stands, a spirit level and a selection of timber off cuts. Probably didn't need to go to as much trouble as I did, but if I'm working on the car people think I'm too busy to interrupt.

Ran some oil through the diff with the drain plug out before filling it.

That block of WTF that attaches to the diff = loads of fun to put back on one handed.

And Hayden, there is no law that states you need to comment on every thread, your comment was useless

It's all good. I was too slow on slipping a one handed joke in there. :P

Is fine, the drag of the tail shaft and trans case causes this, your rear diff is fine by the fact when driven by the tailshaft both spin same way

Rear diff is the only LSD

When you do the trans case call me first so I can tell you how to do it properly

Correct me if I am wrong but isn't the centre diff LSD as well and only the front diff is open? From memory, the rear is torsen and the centre is multi plate clutch type.

Correct me if I am wrong but isn't the centre diff LSD as well and only the front diff is open? From memory, the rear is torsen and the centre is multi plate clutch type.

Pretty sure they might both be viscous coupling LSD's.... pretty sure?

The rear is VCU for sure, workshop manual states "...replace the VCU.... " as a repair when the rear diff' fails its test.

Going to try find out for sure what's happening in the transfer...

Manual confirms viscous coupling also used in the transfer case - LINKY (http://imgur.com/JkSdTdN)

I have a feeling this is a "Panic Thread" and should probably be made to disappear now... :io:

Pretty sure they might both be viscous coupling LSD's.... pretty sure?

The rear is VCU for sure, workshop manual states "...replace the VCU.... " as a repair when the rear diff' fails its test.

Going to try find out for sure what's happening in the transfer...

Just checked. Centre is viscous coupling and rear is mechanical plate type.

Just checked. Centre is viscous coupling and rear is mechanical plate type.

Not sure which manual you're reading, but according to the Workshop Manual I have the rear diff' uses a viscous coupling also - LINK LINKY (http://imgur.com/rSaw5ic)

Rear diff' has VCU labelled on it also I believe?

Interesting fact, the ratios in the front diff, rear diff and center diff have the front wheels turning at a different rate to the rear wheels under normal conditions.

Check my math;

Assume engine RPM = 3000rpm
Assume transmission is in 4th gear = 1.000:1

Transmission Differential ratio = 3.684:1
Center Differential ratio = 0.301:1
Rear Differential ratio = 3.312:1

For front wheel output shafts;
((3000/1.000))/3.684) = 814.3322rpm

For propellor shaft RPM;
(((3000/1.000)/3.684)/0.301) = 2705.4227rpm

For rear wheel output shaft RPM;
((((3000/1.000)/3.684)/0.301)/3.312) = 816.8546rpm

Rear wheels are "turning" at a faster rate than the front wheels. Interesting right? That's only 0.3088% difference and my "theory" is that's its to compensate for the difference in loaded radius between the front and rear wheels (front wheel loaded radius will be less than the rear due to engine+ tranny weight).

Just a fun fact smoke screen to divert everybody's attention away from the fact I flipped out over nothing.

Sorry yes trans case is LSD in a way, it is only to act between the front drive and rear drive however, it does not give frontbwheels the same effect as would a LSD in say a fed car ie in theory a single front wheel could in theory lose traction if that makes sense where as in the rear both would

Sorry yes trans case is LSD in a way, it is only to act between the front drive and rear drive however, it does not give frontbwheels the same effect as would a LSD in say a fed car ie in theory a single front wheel could in theory lose traction if that makes sense where as in the rear both would

This was my understanding also. One day, when money flows freely from my money tree I'd like to put an LSD in the front diff' also to make it a legit AWD. Three LSD's.... last time I did that much I had no grip (on reality).

Skapper, I think the reason for the different gear ratios is to spin the rear diff at a different speed to the front in order to cancel out any "beating" between the diffs. The front and rear wheels spin at exactly the same speed.

Centre diff is a fan type LSD with no touching parts, like a torque converter, so it can transfer torque between front and rear wheels if it detects a slip (like if the spider gears start to turn, it pumps oil to transfer torque). The REAR diff is a wet-clutch type LSD. Both centre and rear diffs can "limit" the slip in order to transfer torque away from the wheels without traction to the wheels WITH traction, they just do it in different ways.

Skapper, I think the reason for the different gear ratios is to spin the rear diff at a different speed to the front in order to cancel out any "beating" between the diffs. The front and rear wheels spin at exactly the same speed....

Ah! That makes sense, thanks.

My understanding though is that both viscous couplings are the sealed, silicone filled, clutch pack type as seen HERE (http://auto.howstuffworks.com/differential5.htm) and HERE (http://www.awdwiki.com/images/viscous-coupling-differentials.jpg)

I did Google this thing to death and couldn't find anything that suggested otherwise?

Rear Differential ratio = 3.312:1

I'm curious where you found this value, as when I went looking I found only values the same as the front (3.684:1) or only slightly different - the Evo 4, 5 & 6 seem to have had several slightly different variations but the front and the rear were essentially identical as I recall.


Just a fun fact smoke screen to divert everybody's attention away from the fact I flipped out over nothing.

:clap:

I'm curious where you found this value, as when I went looking I found only values the same as the front (3.684:1) or only slightly different - the Evo 4, 5 & 6 seem to have had several slightly different variations but the front and the rear were essentially identical as I recall.

:clap:

The workshop manual CD thing? That big bunch of PDF's. The details are tacked on the end of the section covering the overhaul of the AWD transmission.

I'm pretty sure it's in the owners manual in the glovebox to.

The rear diff is a viscous type not mechanical, it has it printed on the diff housing and in the Workshop manual that it is a viscous type, where are people getting the information saying it is a mechanical type from?

The rear diff is a viscous type not mechanical, it has it on printed on the diff housing and in the Workshop manual that it is a viscous type, where are people getting the information saying it is a mechanical type from?

Agreed, the Mitsu workshop manual I have says both centre and rear diffs are sealed VCUs.

Gear oil VCU LSD Hypoid gear oil API classification
GL−5 or higher. Above 10C SAE
90W. Below 10C SAE 80W
0.55 litres
https://lh3.googleusercontent.com/-h-MxolvaSZE/USKm2wnhcLI/AAAAAAAAFek/2WIQiWvMsao/s720/RearDiff.jpg

Part no 16 is the sealed VCU