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Prior to the incorporation of our company in 2008, similar overdrives were marketed by the Rocky Mountain Company.   These early overdrives are similar in many respects to ours but utilize a synchromesh assembly from a Land Rover Series III, Land Rover part  FRC6996.  If you have one of these heritage overdrives, we can help with most, but not all, of the parts.  Please ask us for assistance if you need any parts.

Since our production started in 2008, all our overdrives utilize a more compact and modern synchromesh that has its origins in Fiat cars but was also utilized in the Land Rover LT77 gearbox as the third/fourth gear synchromesh.   This part, Land Rover part FRC9387, is interchangeable with our part but we encourage you to use our version that has a more robust construction.

There are more than 4000 overdrives in service and we are aware of less than  ½ %  requiring spares (other than consumables such as crush washers) in any one year. The chance that you will require a repair part is very small.

Few used ROAMERDRIVES come up for sale and in our experience such overdrives have a high incidence of abuse.  If you are offered a second-hand unit, we advise having the internals checked by a competent mechanic before parting with your cash.

When an overdrive has suffered abuse from being driven with lack of oil, or has been damaged on a vehicle with an overpowered engine, it may have suffered overheating damage that is beyond economical repair.


If you send us an email regarding spare parts or repair, please include a clear photo of the name plate showing the serial number of the unit.  It will also speed things up if you open up the unit and take pictures of any damage you observe.      

There are three deep groove ball bearings in the overdrive and all can commonly be purchased from any bearings supplier.  There are no rotary oil seals.

DS Schematic and Parts List

SS Schematic and Parts List

Generally speaking, repairs can be done by any person with mechanical skills and access to a hydraulic press.

We have a policy of incremental product improvement and since our founding we have made several minor changes in construction.  If your overdrive can benefit from such changes during repair, we will advise you.