In <3060262E@msgate.reston.unisysgsg.com>, Unger, Larry @ RES wrote:
>
>The rear on my '62 MGA is covered in grease ... rotating a rear wheel
>reveals a great deal of play and produces a noticeable *clunk*. The
>hubs for the wire wheels are in good shape ... so my assumption is
>that the DPO failed to either replace the front seal or keep the grease
>topped up ... resulting in excessive wear to the differential. The
>assembly procedure, outlined by the factory workshop manual,
>requires several specialty tools .. any suggestions on where I might
>get my differential refurbished?
>
Aaah. The Dreaded Clunk. First, it is not all that unusual for the
rear end to be covered in grease. A lot of it is blown back from the
engine, so it may not originate in the rear end. There are two
places where Clunk develops, one easy to fix, the other a swine.
Unfortunately, to discern between the two requires removal of the
chunk (the gear housing) unless you have a very delicate touch.
There are two mechanisms in a differential. One effects the right
angle conversion and involves the ring and pinion gears. This is an
extremely precision setup and if you have excessive wear here you do
indeed have trouble. There should be a very slight amount of play in
the clearance between the ring and pinion. This can be determined by
observing motion of the ring whilst gently rocking the input shaft
back and forth. (Note that this is very difficult to judge just by
holding the axles still, as will be developed below). In general the
spec on the clearance is something less than a millimeter--it's in the
shop manual. There should be _absolutely_ no lateral play or
fore-and-aft play in the input shaft. If there is, your pinion
bearings are shot and replacement is doable but tricky. You also
might try cleaning the glop off the diffie case behind the input shaft
shield so that you can watch for leakage there, to see if in fact the
input shaft seal is shot. You can replace the input shaft seal with
only a moderate amount of trouble and the only special tool required
involves a length of angle iron.
The ring gear turns a cage that holds the differential ("spider")
gears. These in turn bear on the axle gears. This is usualy where
the clunk develops. Both the spider gears and the axle shaft gears
bear on thrust washers that wear out. Even a couple of thousandths
of wear on these washers results in noticeable slop between the input
shaft and the rear axles. The washers can be gotten from Moss, among
other vendors, for a few dollars, and are easily replaced once the
chunk has been removed. Note that in some cases (with a lot of miles
or bad lubrication) the spider gears themselves are worn to the extent
that there will be some clunk even with new thrust washers. Ignore
it. Your car will continue to soldier on. The only warning here is
to insure that you use a _new_ split pin to anchor the spider gear
shaft when replacing it. If this shaft comes loose it will
immediately lock the rear end, which can kill you.
Use 90w EP "extreme pressure" lube in the rear end. Fill until it
starts oozing out the fill hole. There will always be some leakage,
which accounts for the goo all over your unit.
A. B. Bonds
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