Tech Tips for your Jag IRS Differential
Dealing with Your Jag Differential
Probably the most common major component problem with Jaguar automobiles is carrier or output bearing failure in the differential or rear axle unit. Jaguar diffs will usually develop the characteristic whine of a damaged and failing bearing by at least 100,000 miles, in some cases sooner, but in almost every case by 125-130,000 miles. As an aside, bearing noise from the rear of your Jaguar can be from the wheel (hub) bearings but is much more commonly from the differential bearings, says 80% of the time.
There are two main reasons why this occurs. First, the design of the Jaguar independent rear suspension uses the axle half-shafts as the suspension's upper control arms. This is why the axles have normal U-joints (rather than CV joints) and also why the axles do not have sliding splines as many IRS setups use. This design, which is more commonly used on racing cars, feeds additional thrust loads into the output shaft bearings as the suspension compresses and shortens their service life. Excess play in either the U-joints or the output shaft bearing will allow the rear wheels to tilt out at the top. (To check this, jack up the rear of the car and place your hands on the wheel at 12 o'clock and 6 o'clock and pull outward. There should be no significant movement of the wheel.)
Second, Jaguar does not list a differential lubricant change as part of the scheduled maintenance, as most other manufacturers do, usually at 30,000 mile intervals. Our experience is that changing the diff lube will delay the inevitable failure of the diff output bearings. We also feel that the use of a synthetic gear lube, of the appropriate viscosity, will extend the life of these diff output or carrier bearings.
If you have a diff with a noisy or loose output bearing, it is not recommended just to replace that bearing and stub axle as the metal particles thrown out by the failing bearing will usually damage the other bearings in the diff in short order. And if you have an inboard brake Jaguar, such as an XJ6 Series 1, 2, or 3 sedan or an XJ-S, be sure to replace the rear rotors at the same time as the differential; either procedure requires dropping the rear suspension assembly from the car. This is not a job you want to have to do twice!
WE found this article on the internet and thought it might be of interest to some of you Jag IRS owners.
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