Rear End Noise
by Art Isaacs
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Q: I have noticed that when I shift gears, frequently there is a little chirp that seems to be coming from the rear end. There isnít any other rear end noise that I can identify as being out of the ordinary but that isn't saying much. Can you offer any ideas on what may be going on and what I might want to check to correct this problem.
Q: I suspect the fiber thrust washers in the differential have either worn or dropped out completely. The thrust washers are available from Moss (P/N 265-270, $9.40 each) and you need 2, one for each of the pinion gears
Very common on MGBs, the fiber washers wear to the point that they are thin and brittle, break and fall into the bottom of the differential housing leaving excessive clearances between the differential pinion gears and the housing, The classic "clunk" occurs when either dropping-off or pressing the accelerator, like when shifting.
Replacement is involved, but not terribly difficult. If you want to get an idea of the job, Mark Evans (Discovery Real Time - "An MG Is Born") did this job himself in building-up a 73 MGB, though I suspect much of the work was done off-camera. You can probably do it yourself or get most any axle or transmission shop to put replacements in. I have no idea the cost, but can tell you my local trans shop gave me a $150 discount coupon toward rebuilding a differential. If that's the discount I can't wait to see the full price.
I hope that helps you. Let me know what you find. Good luck.