1968 buick wildcat diff info

[Guest jtotheb]

Hi Guys I'm a newbie to the site, I own a 1968 Buick Wildcat that has developed an intermittent rattle from the rear diff sounds like a chain rattling! any ideas what it could be noticed that the diff oil is low,also what diff oil should I use and do I need to add an additive, thanks in advance for your help:)

[NTX5467]

Not sure about the sound. Might need to pull the cover and look inside. Usually, internal noises in the rear axle are more like "hums" which can vary with speed and load. Wheel bearings can sound similar, but can increase and decrease as the loading on the particular rear wheel is changed (as in swaying the car side to side or applying the foot brake lightly). Generally, all things considered, if there's anything loose inside of the housing, it could get between the ring gear and pinion gear and make things come to a tire screeeching halt.

The rear of the two-piece driveshaft attaches to a yoke, which is attached to the pinion gear of the differential. Many times, there can be a shield which is tack-brazed onto the yoke, to protect the outer pinion grease seal. If the shield might become loose (some were just tightly pressed onto the yoke rather than being tacked), it can rattle. If that's where it is, that's an easy fix to get it firmly reattached to the yoke, but the yoke will need to be removed to make the repair.

As to rear axle lube, it should be the normal 90 lube that's been around for years. Unless it's a limited slip differential, no GM Limited Slip Differential additive is needed.

Might not be a bad idea to change the rear axle lube, anyway, for general principles. You can find "the normal stuff" at any auto supply or GM dealership. Usually in quart (or thereabouts) plastic bottles.

You also might consider sliding on over to the Buick areas of these forums, too.

Enjoy that 'Cat!

NTX5467

[Guest jtotheb]

Thanks for your help much appreciated I will check it out.