Spares are a concern when servicing a high mileage V8 back axle
Gordon Hesketh-Jones (Harvest Gold 1904) from Cornwall has clocked up over 400,000 miles in his MGBGTV8 and relates his experiences with spares for back axle servicing. (Nov 08)

Parts diagram: page 22 MGBGTV8 Parts Supplement MGL001B (Moss)

About 80,000 miles ago I started to hear a clicking noise from the differential every time I took my foot on or off the accelerator although the differential on Harvest Gold 1904 was still delightfully howl-free, unlike some of the new Italian-made ones I have heard. Obviously I checked and re-checked the universal joints on the propshaft but they were still both quite new and in good condition, so I drove the car along to Cornwall & Devon Transmissions at St Austell. After a test drive and an examination they felt that the wear was in the crown-wheel and pinion - which obviously did not fill me with joy. So a few weeks later I stripped the back axle from the car and took it to them. I was then delighted when they phoned to say that the CWP was in excellent condition but just needed re-shimming and that also all seals and bearings needed routine replacement.

More recently the ominous clicking started again but with the differential now having covered well over 400,000 miles I felt I really could not complain and made another trip to
St Austell. After the road test their engineers were a bit puzzled but examination on a hoist made it clear that this time the clicking was coming from the front nose of the differential casing. Once again the axle was stripped out, brake hubs removed etc and off it went to St Austell, but this time the news was not so good for both of the two pairs of planetary gears were badly worn. Worse still was the fact that of the larger pair (BTB428), MOSS had just one single gear in stock @ £103.70 plus VAT, whilst the smaller pair (BTC9001) had the dreaded "NLA"
Section G: Rear Axle & Propshaft Assembly

Parts list: page 23 MGBGTV8 Parts Supplement MGL001B (Moss)

(no longer available) marking on the MOSS computer. In addition the collapsible spacer (BTB853) was also NLA. I phoned around to Rimmers, Brown & Gammons, Clive Wheatley, MGB Hive etc but without success and depression set in.

More research on the MOSS catalogue made me realise that the MGBGTV8 differential is virtually identical to that of the standard later-model MGB, apart from our 3.07:1 ratio crown-wheel and pinion of course. Now, many years ago at a workshop clearance sale I had bought a complete MGB axle; I knew that my planetary gears had been OK at around 330,000 miles, and even though I did not know the history of the standard MGB axle that had languished under my work-bench for around 12-14 years, I doubted if it had even covered 50% of 330,000 miles. So another drive to St Austell, hoping madly that the gears in that back axle were in good condition and could be used along with the rare collapsible spacer that Tim Kelly had found for me. The result - success and a minor bill for £322 which included £70 plus VAT for numerous new bearings and seals and also the strip-down then re-assembly with my spare axle. The rebuilt V8 back axle is now totally silent again.

The moral is clear - if you see an MGB tube-axle for sale at a reasonable price - BUY IT!
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