Common causes of axle failure
The Derby Bentley and Rolls-Royce 20/25 are, in many instances, running on original rear axles which have been providing service for over 75 years.
This is testament to the excellent attention to detail and workmanship of the original components.
However, with the passage of time and years of use, wear and fatigue to moving components can cause noise, vibration and eventually failure.
The 3 ½ and 4 ¼ Derby Bentleys were designed as high performance sports cars of their day and with this in mind the weight of the rear axles had to be reduced to a minimum in order to obtain a low unsprung weight.
As a result there are some components which can fail as a result of age and load related stress. Failure of the pinion thrust bearing can result in oil leakage and/or excessive noise from the rear axle.
Similarly, on Rolls-Royce 20/25, bearings can become worn and break up as these represent some of the weakest points in the axle and bear a considerable amount of the workload.
Hub and halfshaft related failures
We have also seen and attended to several instances in which the planet gear crosspin has catastrophically failed causing internal damage to gears, bearings and casing.
This is a result of old and fatigued hub bearings together with wear to the splined hubs and drive dogs. There is a tendency for driveshafts to crack at the splines and also at the ‘sun gear’ end. It is therefore essential that hubs, bearings and half shafts are inspected for cracks, wear and play and that affected and suspect parts be remedied prior to installation of the newly overhauled axle.
Derby Axles will carry out this work where required, with many parts available from stock.
The importance of ‘gear mesh’ and correct tooth patterns
Many of the axles receiving attention at Derby Axles have been presented by the owner as noisy either on ‘take-up’ or ‘overrun’. This condition has usually been found to be incorrect ring gear to pinion tooth contact.
Attainment of correct meshing and tooth patterns can often be the most laborious and time-consuming phase in differential overhaul, but it is most essential in providing the owner with an enjoyable experience of the axle once fitted back to the car.
We have the required experience gained over 20 years axle overhaul to know when the axle looks and ‘feels’ correct. We will revisit the axle as many times as necessary during the setting up process and make adjustments until we are happy that it is right.
There is no additional cost to the owner for this service as Derby Axles always provide an up-front fixed price for labour.
Premium quality bearings
Derby Axles use only premium quality bearings to original maker’s specifications. These are manufactured to exacting modern standards as we want your rebuilt axle to last as long as the original.
Standard and higher ratio crown wheel and pinion sets
Axles can be rebuilt using the owner’s original standard gears provided the crown wheel and pinion are serviceable with no tooth damage or deterioration. The gears will be thoroughly tested and re-lapped prior to installation to compensate for any wear or minor deterioration cause by worn or damaged bearings.
Standard ratio gearsets are available from stock if required.
Higher ratio gearsets can be supplied to order if required. These result in a more useable 1st gear on modern roads and quieter, smoother and more economical performance.
Please contact us if you would like more information on higher ratio gears and their benefits.
Specialists with fixed labour prices
Derby Axles are specialists in axle overhaul for pre-War Rolls-Royce and Bentley motor cars. We particularly specialise in Derby Bentley and Rolls-Royce 20/25 but will undertake work on other pre-War axles by appointment.
We enjoy working on axles and the largest percentage of our work comes from recommendation. Our aim is to offer owners top quality service at sensible prices and with no nasty surprises and so we offer a fixed price promise on our labour charges.
This assumes that the owner arranges for the axle to be removed and re-installed following overhaul.
We can provide additional facilities for removing and re-installing the axle into the car by arrangement and at additional cost.
Parts are supplied at, or where possible, below competitors prices and we will continue to keep you informed of progress and any parts requirements throughout the project to completion.