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Posted: Tue Jun 29, 2010 7:02pm

Post Subject: PRM gearbox

We had a new PRM120gearbox fitted just over a year ago and it has been working all right. However recently it has developed a grating and a grinding noise going into forward gear. Reverse seems OK with just the usual clunk. Any suggestions for adjustments or different oils?


Posted: Tue Jun 29, 2010 8:07pm

Post Subject: PRM gearbox

Dear David, This is a mechanical box so as long as the clutches (in this case the ahead clutch) are OK then there should be very little to make grinding noises on such a new box. As far as I am aware there is no adjustment on the gearbox save cable adjustment. The down-loadable manual from PRM says you should be using engine oil in the box so something like a 15W40 or similar should be fine. If you have red automatic transmission oil in the box try changing it for engine oil. However I doubt its an oil problem. Disconnect the cable from the small lever on the gearbox and try engaging ahead by manually operation the lever. If it does not grind I suspect a cable adjustment fault, something causing loss of movement (like a loose lever in the control or one of the cable anchors coming undone. I have a horrible feeling the dive-plate that is fixed to the flywheel may be breaking up if it was not changed with the gearbox. To check it the gearbox needs to come off the engine so its not a typical DIY job. AS the box is so new I think it might be a good idea to speak to PRM & your supplier about this. Tony Brooks

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