Transfer case strip down

We had a legnum vr4 that came into work with a noisy transfer case. Due to high labour rates it worked out cheaper that they just had a second hand one fittted than repairing theirs.
So i have managed to get my hands on it to bring home and strip to show you guys the guts of it. They are not too different to a normal diff you would find in a non ayc.
Anyway I have started stripping it down. You first want to remove the bolts that hold the crown wheel and diff in. This will help to reduce the weight of the thing.


Next part just remove all remaining 14mm bols that hold the tail housing on. It also pays to tap the drive shaft cover off befor unbolting to make life easy. Just remember that it is safe to remove each step of this if you have a leaking box. You don't need to worry about getting the gears out of mesh or other issues.
Now sitting here are all sub assemblies that make up the transfercase. A few have an o ring between parts to seal. I think i could guess and say that this is where your oil leaks would be coming from on these boxes.

Is it possible for you to open up the viscous coupling unit that is inside the part with the crown wheel?

I have not had a good look as i am wanting to clean it up first. I am thinking it is a sealed unit into the spider gears. there is a ring of bolts but i am guesing it is just to holdd the crown wheel on.

What do you do for work Nathan?

I am a servicce advisor for Mitsubishi but i am also an ex mitsi factory trained tech

As usual, nice work Nathan Do you know how many kilometers that car had done?

i am unsure will have to look through the job car when go back to work on tuesday. i would probably guess by looking at the car around 140k

For those interested, I have my transfer case apart at present for the ACD conversion I am doing.

Here are some pictures

1: The assembly after removing the crown wheel.

2: Once split, we have the rear drive to the crown wheel and rear VC (Viscous Coupler) segment. Next to it, is the front diff still mated to the VC

3: The rear drive, the VC and the front diff. The front diff locates inside the rear drive housing and runs on carbon bushes between the rear drive housing and the VC. In this manner the front diff would be free to spin inside the rear drive housing, however being connected to the VC provides limited slip operation.

4: The front diff.
On the left is the external view where you can see the input splines from the gearbox at the bottom, and the splines that mate with the VC at the top. Note that these are solidly part of the outer diff housing and take the place of a crown gear were it a more traditional layout.
To the right you can see an internal shot which shows the output shaft splines which goes to the passengers side wheel. You can see the splines for the drivers side in the picture to the left.


5: This is a helical (Torsen) replacement for the front diff. NOTE: This DOES NOT fit inside the standard rear drive housing as it is 2mm larger in OD. You would need the drive housing from a Evo which has a helical front diff as standard, and either the crown gear to go with it (if it isn't stuffed) or you need to grind the ID of the standard crown gear larger (what I am having done)

6: The VC with the front diff splines clearly visible. If you want to know how a VC works, google: "How Viscous Coupler works" it is a very simple arrangement. The VC is sealed.


The most common issues with transfer cases are
1) Crown and Pinion wearing due to poor maintenance (includes rubbish gear oil) and the fact that a hypoid gear arrangement is designed to have the crown driven by the pinion, rather than the other way around as is done here. This apparently causes much excess heat which can, if your oil is low or rubbish, cause lubrication issues which kills it. Symptom is whining.

2) The spider gears in the front diff are not very strong. If you load them up, they will explode and destroy the front diff and the inside of the diff housing. With Evos, this apparently is common when getting front wheel slip when launching. The quick load/unload action on the diff is more than it can handle and it gives up.

Those are some real good photos, good to see it does pull apart when removing those bolts. I cant see any wear on the crown and pinion and the brief look i had at the bearings showed no signs of pitting.

For the ACD will you be running a Centre Diff Controller?

What is involved for the conversion?

I've got a stack of pics of my one I pulled apart too if anyone wants them.

Kenneth u have a shiny and clean transfer case

Yes, I will be using an ACD controller when I can afford a decent one. In the mean time ill either use a standard ACD ecu, or just leave it disconnected.

The camera flash likely makes things seem a bit shinier than they are, however the transfer case was in almost perfect condition internally... no sign of wear on the crown gear after 100,000km. I like to think it is due to good servicing.

Has Anyone rebuilt one of these? What did they find...were the gears worn, bearings what is the common point of failure? Is there a rebuild kit available? Sorry for all the questions, I suspect my transfer case might be gone! I am planning to drop the oil out and inspect it but I fear that I might not like what I see. And Paul I would like those pics too if you have still got them...

All the seals are available as I've replaced mine, but ASA doesn't show any internal components available. It's possible there could be aftermarket Evo related sources for them though.

Thanks I will look into aftermarket evo parts I am sure that the bearings can be sourced I am just trying to estimate the possible cost of rebuilding it as opposed to putting in a second hand one.

Size1 said:

Has Anyone rebuilt one of these? What did they find...were the gears worn, bearings what is the common point of failure? Is there a rebuild kit available? Sorry for all the questions, I suspect my transfer case might be gone! I am planning to drop the oil out and inspect it but I fear that I might not like what I see. And Paul I would like those pics too if you have still got them...

Click to expand...

I have rebuilt one of these. It had a nasty whine. I found that the gears were melted and I installed a good second-hand gearset and full set of OEM bearings and seals. I found that it was just like an EVO4. I would suggest that you have yours repaired by a qualified, licensed and experienced mechanic. Good luck there LOL.