Hi there,

I've noticed that my differantial is starting to whine... Not a nice thing to have (I know the XJ40-X300-X308 diffs like to do this) but it seems to be starting now...

What causes this problem? I doubt Jaguar ignored it since 1986 as the first of these massive diffs had this problem... Is there an improved version? Or can some improved parts be fitted to stop the whine?

What part is it, that causes the problem? I would assume one of the "in-shaft" (assuming there are two)... Or can it be a lack of transmission/differential fluid?

Cheers

Damien

 

If it is a high pitched whine then it probably is the pinion bearings.
I have replaced dozens of the XJ40/X300 pinion bearings but I only had one X308/X100 diff apart to install a QUAIFE LSD unit to the crown wheel. I didn't need to remove the pinion so I can't say if they are the same. I don't know if bearings are easily obtainable.

bob gauff

 

I would be surprised if the pinion bearings are the same between 15hu and 14hu. The part numbers are different but that does not mean the bearing numbers are different. I have a feeling most of the wear and failures in our 14hu diff rentals are caused by worn/wear in the output bearings. The output bearings take a good amount of extra force because the axle acts as the rear suspensions upper arm. i believe some of this wear can be increased by clogged/bad diff breathers (common issue) forcing dirty diff oil into the sealed output shaft bearings. The output shaft bearings have a rubber seal that faces the center of the diff; increased case pressure + normal wear will compromise the seal. Any extra play in the output shaft could cause the ring and pinion mesh to change leading to extra wear in the gears and bearings. Unlike the xj40 and x300 with the 15hu, the x308 and x100 use an on-center/spiral gear ring and pinion: the axis of the pinion gear intersects the axis of the ring gear. The main disadvantage of this set up is strength. Only only one tooth on the pinion gear can contact at a time. The older cars use a more conventional hypoid ring and pinion that allows for more contact between the gears therefore is stronger for a given size then a spiral gear set.

The next big item i have for my XJR is replacing the diff; I have a low mileage diff sitting next to my tool box! (and new output shaft bearings).