Everything here is after the case has been apart and washed.
The transfer case bolts to the transmisison and there are 3 concentric shafts going from the transmission to the tranfer case. Then there is a second shaft in the transfer case that is only there to direct power to the rear wheels.
For the main shaft, the outer most shaft is the output from the cars transmission to the transfer case. This turns the planetary differential, and the power is split 60:40 Rear-Front. the Front output is the middle of the 3 concentric shafts and it passes back into the car's transmission where the front differential is. the LH front shaft exit directy to the LF wheel. The RH front output from the front diff isthe inner of the 3 concentric shafts and passes directly through the tranfer case, out to the RF wheel . This shaft is called the Link shaft. It is not in these pictures.
The rear output from the planetary differential is driven by a gear to the second shaft in the TC. this in turn goes to a 90degree turn and out to the rear output flange.
First pic, is case in the normal position. The rear output flange and gear are removed.
next I put the case with the RHS up and removed the cover, this pic shows inside the cover,
here is the open transfer case, with the main shaft and the rear output shaft in place.
the VC lifts off the main shaft I dont know what is in place for the later model x-type that dont have a VC, there must bea spacer in its place.
the case with just the second shaft.. for rear output.
The rear output of the planetary diff is the outer ring around the small gears. it is driven on the inside and the outside has teeth that mate with the second shaft in the TC. It just lifts off. There is a little thrust bearing behind it. It is fairly important to understand that all these parts turn at the same speed when the car is driving along in a straight line. The little planet gears dont spin much unless either the front or rear are slipping.
The Viscous coupling has an inner splined part and the outer part has 4 large pins, the splines slide onto the front output shaft, and the pins connect to the rear drive gear. The VC is a sealed unit and it is very hard to turn the two parts. The resistance gets bigger the more you try to turn it.
Last pic show how there are a few chips on my rear drive gear, My TC is not particularily noisy, and I dont see any damage on the mating gear. I cant say what caused the damage. I am not going to worry about it.
I'm with Christo on this, what is the weak link inside the transfer case? I am betting it is either the viscous coupling or the small gears between the coupling and the tranny input. I wonder what could be done to "upgrade" the transfer case to make it more bullet proof (for those wanting more power out of their cars). I'm sure with a bit of work, you could have some chrome moly gears made and possibly even cryo-treated. Sure, it won't be cheap, but would be lots of fun to have an X-type that people think is slower than their car and then get smoked by it.
Chris "Thermo" Coleman and K'Re Ann, the 03 X
Ha, well in fact I am a mechanical engineer.. - presently unemployed. the automotive world is not so hot.... - anyone looking for someone like me?
My background has been in light alloy die casting, and can you guess what parts I am most familiar with? you got it .. transfer cases.
one place I worked for almost 10 years is a huge supplier for magnesium TC castings. Mostly for GM and Ford trucks/SUV
I dont know if there is a weak link per say.. But over alll this is clearly a car transfer case and not a truck one.
I have 11 years of experiencedriving BMW 325iX - built from 88-91, before I got theJag. I have had to repair, rebuild swap that transfer case 3 times.
The reason these things fail is 99% from running out of oil. The bearing will get worn quickly with no oil. The BMW case was a different design, and the rear shaft was driven by a chain.
The chain would quicly wear and get longer if it was run dry.. then the chain would jump on the sprockets.
The only real thing you can do is make certain that you have clean oil in there.
The BMW TCseemed to have heavier duy ball bearings compared to the tapered roller bearing on the Jag, but I have not looked up their specs... (too much research for no benefit to me)
I spoke with a montreal parts guy at a dealer here.He tells me that they could repair a whole lot of the TCs they end up replacing just because a few parts are not available.
I think eventually as the X-types fall into the hands of more and more DIY guys.. we will get these parts eventually. (bearings and seals)
Don't expect the VC to be the weak point. I'm an owner of several VW Vanagon Syncros, which use a VC to transfer power. While it can fail over time (two different modes of failure btw) it usually lasts a very long time. 20 or more years in some cases...Being a sealed unit, there is really hardly anything that can go wrong with it during it's service life.
In the VW world the VC failures can be...loss of power transfer (rare) or overly agressive transfer (a little more common, but still not particularly common). Overall it is a very simple mechansim that gives good long service life.
Lack of lubricating oil wouldn't affect the VC, but would damage the bearings.
This is my personal opinion from inspection of the cases I've changed. Case flex is the major contributor to t-case failure, then operator headspace, then lack of lubrication. 90% of the cases I've changed were catastrophic failures with nothing left to rebuild. These transfercases aren't built for high load power application, they are built to a cost effective level of performance for their intended use. It's abuse that kills them.
I cannot see through steel.
I cannot predict the future.
I cannot sh*t parts.
Bo did pull his pics. You'd have to try to reach him elsewhere.
03 S Type R - Mafioso Intake+K&N, Akebono pads F&R
07 SAAB 9-3 turbo - BSR Intake/Downpipe, ECU tune, Powerstop rotors and pads
07 Jeep WK 4.7 2" BDS Lift, skids, bull bar, AT3's
06 Jeep XK Commander Limited 4.7 - K&N FIPK, Mopar Skids, Cooper AT3's - planning air suspension
Ex 2002 X Type owner