I have a 1990 Ford cargo library bus that I have converted to a motorhome. The vehicle drives well, but the top end is very slow. Around 45mph and the rev are in the red. I thought of fitting a 5 speed box, but was recently told it could be the differetial. I have checked the plate on the rear axle, and it gives the ratio as 5.12. Can anybody enlighten me?

Steve, September 2008

Firstly are you sure it only does 45mph or is that just what the speedo says. Check it with your car or something. If the worm gear on the gearbox end of the speedo cable has been replaced BY THE WRONG ONE in the past, then your speedo will be all to pot.

The other problem is if someone before you has fitted a replacement gearbox from a scrap yard as the original was knackered. They may have fitted the wrong gearbox, it works ok but the gear ratios might be wrong for the engine.

You can get the serial numbers and chassis numbers and speak to Ford who might be able to assist you with this.

Make sure you have a "matched" gearbox and engine before you start spending money changing stuff.

JB, September 2008