Rear axle noise on the over-run
Discussion
If it is a 'diff whine then change the oil ASAP. It's likley the Shell Spirax 90 orgional fill oil has degenerated to the point some wear has taken place and gears are moving out of the correct mesh pattern due to that wear - hence the noise.
Assuming it's a V8 not a 6cyl, you'll need some form of suction pump to get the old oil out through the filler plug. I made one up from a petrol can, some tubing and an industrial vacuum cleaner, but you can buy an oil extract pump from most boat chandelers. Taking the car for a drive first to get the oil hot and thinner makes life easier. On an XJR you'll have to remove the rear anti roll bar to access the filler hole.
You can use any API GL5 EP 90 oil but I like the Morris lubricants Lodexol full synthetic 75/90. If the noise has got bad enough that an EP 90 change does not make any improvement, then you can usually quiten a whiny 'diff down a bit by using somthing like Penrite EP 140. I know this is not the right 'spec oil for an XJ and I wouldn't usually suggest using it but I know from experience it works a treat and if the 'diff is that knackered a slightly thicker oil can help - and it may even slow down the rate of wear a little.
Assuming it's a V8 not a 6cyl, you'll need some form of suction pump to get the old oil out through the filler plug. I made one up from a petrol can, some tubing and an industrial vacuum cleaner, but you can buy an oil extract pump from most boat chandelers. Taking the car for a drive first to get the oil hot and thinner makes life easier. On an XJR you'll have to remove the rear anti roll bar to access the filler hole.
You can use any API GL5 EP 90 oil but I like the Morris lubricants Lodexol full synthetic 75/90. If the noise has got bad enough that an EP 90 change does not make any improvement, then you can usually quiten a whiny 'diff down a bit by using somthing like Penrite EP 140. I know this is not the right 'spec oil for an XJ and I wouldn't usually suggest using it but I know from experience it works a treat and if the 'diff is that knackered a slightly thicker oil can help - and it may even slow down the rate of wear a little.
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