My main reason for writing concerns the article on the MGB rear clunk. This article, while very good in what it says, is a bit too simplistic in what it explains in the way of the complete procedure, and if not further detailed, could easily cause quite a bit of grief to the novice who tries the procedure as explained in the article. Over the years, I have completed, or helped others to complete, somewhere in the neighborhood of 50 of this operation, and while not really difficult in itself, the person attempting this operation for the first time, and following Chris Nowlan's John Twist-inspired article to the letter, may well run into trouble that will be irreversible. I will attempt to clarify how I do this.
Raise the rear of the car and place jack stands under the front of each leaf spring hanger. Allow the axle to drop to its lowest point, suspended by the rebound straps, and drain the differential oil. With the handbrake on, remove the left rear wheel, hub split pin, nut and hub, followed by the handbrake cable from the left and right brake levers, and from the differential cover plate. Now remove the cover plate.
Now comes the very critical part which was passed over in Chris Nowlan's article. Rotate the differential unit until the small roll pin can be removed with a small drift. Then, rotate the differential unit until the roll pin hole is at the top of the unit. With a hammer and drift, slowly tap the main pinion pin upwards, but only until the small roll pin hole is just visible, and clear, of the top of the differential cage. Now, rotate the differential cage and the protruding pin rearwards until the pin is facing downwards.
Insert a suitable bar into the small roll pin hole and twist/turn/pull the large pinion pin downwards until it is free from the differential cage. Some pins are much tighter than others, so do whatever/use whatever is necessary to free the pin - persevere, and it really will come out. Under no circumstances should you attempt to drive the pinion pin out into the nose (front) section of the differential casing, and do not drive the pinion pin much above the point where the small roll pin hole is visible above the top of the differential cage. If you move the pinion pin too far, it will make contact with, or will not clear, the inner surface of the differential casing, and the differential cage will then be impossible to move in either direction. Once the pinion pin is moved too far upwards, there is no way to move it back into the differential cage so as to rotate the cage itself.
The copper thrust washers easily fall to hand, as do the small gears. Now we must remove the side gears through which pass the axles, so as to remove/replace the fiber side thrust washers (you may find that the old thrust washers have simply disappeared, with their remnants in the gear oil). To do this, you must partially pull one of the axles; I recommend the left hand axle. I pull the left side because if you remove the alloy strap which holds the left wheel brake pipe to the axle case, you will have just enough slack to ease the left backing plate, complete with wheel cylinder, brake shoes and brake line still attached, over the end of the axle. This movement is needed for enough clearance to remove the side gears to install the fiber thrust washers, but it is far easier to simply remove the axle, as you can then inspect the axle bearing, followed by replacement of the axle oil seal when installing the axle.
As the English say, installation is the reverse of removal! It is a rather straightforward procedure, but it is also quite easy to damage the copper thrust washers while installing the pinion pin into the differential cage if these copper washers are not lined up exactly with the pin. The pinion pin can only be installed from the bottom, moving upwards, and the top copper thrust washer is a bit difficult to center, to allow the pin to pass through the copper washer without damage (it would be nice to have an extra copper thrust washer available, just in case?).
The entire process isn't too difficult, but if possible, I would recommend doing it the first time with someone who has already done it. It really does eliminate the "clunk", reducing pinion rotation down to 1/8 inch or less. I commend you for your insight in offering the article for publication and I offer the above only for a bit more clarification of the procedure.
(Robert will receive a gift certificate for his contribution.)
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