Diary of a rear axle rebuild

1932 Rolls-Royce 20/25: chassis # GZU7


Adapted from an article written by

Jonas Trachsel, Switzerland.


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This section of the web site is a record of the axle rebuild of GZU7 owned by Jonas Trachsel, Switzerland.  The work was undertaken by Jonas and Richard Treacy during the period November 2006 and March 2007.

Introduction by Jonas Trachsel


To begin, I had worrying expectations on the causes of an increasing, unidentified noise in the drive line of my 20/25 hp GZU7. Before the ground-up restoration a few years ago, the rear axle was faultless in use. It was quiet and worked perfectly, so my decision was that it was best cleaned, serviced but otherwise left well alone. The gearbox was in the same excellent state, also being faultless in every respect. I decided that these two major components would safest be left simply well maintained. After quite some research, I elected to have an overdrive fitted to suit modern highway driving rather than to alter the final drive ratio by fitting a revised crown wheel and pinion, and perceived no immediate reason to have the rear axle opened. Things change. After some thousands of miles I was sickened that a slight humming or singing noise when under load had started to become noticeable. The singing disappeared completely when coasting and on overrun. As this sound did not change dependent on the selected gear or with overdrive, the pitch dependent purely on road speed, I assume it to come from the rear axle. The fact that the overdrive did not change the pitch excluded the gearbox as a source of this noise, so it could only have been coming from the output of the overdrive or from the rear axle. The overdrive is new, so I was fairly sure that it was coming from the rear axle.

At this point, I contacted several authorities on RR matters and was very fortunate that Richard Treacy agreed to assist me with this major rebuild.



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Removal of the rear axle
Click for 5 x images - 269KB
Brake drum removal
Click for 9 x images - 556KB
Dismantling the axle
Input pinion assembly
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Re-assembly of the axle case
Click for 14 x images - 868KB
Refit axle in chassis
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