The MGA With An Attitude
CLEANING INSIDE Of The Rear Axle Assembly - RA-111

On 30 August 2012, George Goeppner in Illinois, USA, wrote:
"Time to refill my differential as part of finishing restoration of the chassis assembly. Has anyone ever run a flush thru the diff when changing diff fluid? Seems like it might drain out old crap from years of use, but I don't know".

I will guess the answer is no. Does the existence of this question imply that you restored the car without restoring the rear axle? If you replaced hub seals you likely already cleaned the hub rotating bearing housings, or you can do that in situ.

You could fill the center housing with mineral spirits and drain it a couple of times, but that only gets to the lower third of the center housing, and does not necessarily guarantee getting out hard settled residue in the bottom. Without driving the car the flushing fluid will not get into the upper 2/3 of the housing or into the outer reaches of the housing arms.

The lube system works by the bull gear splashing oil into the upper part of the housing where is can run forward to the input pinion gear. There are "gutters" along the top of the outer arms of the housing that catch splash oil and carry it outward to the vicinity of the wheel bearing hubs. From the outer extremities of the assembly oil drains back to the center sump by gravity.

To get this flushed without disassembly you would have to fill it with some sort of flushing fluid, mineral spirits for instance, then drive it for at least a few miles to circulate the fluid, then drain it and refill with gear oil. To get most of the flushing fluid out of the wheel bearing hubs you would need to drive it some more to circulate fluid, then drain and refill it with gear oil again, maybe a couple of times.

I cleaned mine out once after a differential failure. I removed the halfshafts and the differential and drain plug leaving an empty housing with the open wheel bearing hubs still in place. Then I used a long pipe brush soaked in mineral spirits and turned the brush with a slow spinning power drill. I also washed out the center housing with mineral spirits and paint brush. If you intend to get into the upper gutters for cleaning you might need a fat rifle (shot gun) cleaning brush.

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