Hi,

You might also check that the breather tube is not plugged because this can cause pressure to build in the rear end. You'll find it at the top of the axel tube on the driver's side, about midway between the pumpkin and the wheel.

As for when to change oil, I came across the owner's manual for my 67 IHC pick up the other day and was amused to read that they recommend rear end oil changes at 10K or twice a year, whichever is less. The axel is pretty much the same as is on a 240.

Volvo's recommended interval is never, so my guess is somewhere in between. I think it's more a question of what type of driving you're doing rather than strictly mileage.

If you have 170K on the car with the original inner seals it's probably time to change them, and you can clean and repack the bearings at the same time.

Peter