Changing the gearbox piston seals


I recently changed the piston seals on my RM gearbox because there was a hissing and bubbling from the gearbox in 1st gear.


You need the replacement seals and three gaskets for the cylinder heads of gears 1,2&3, 4 and reverse. Try for these.



On this picture of the underside of the gearbox you can see the cylinder head for 1st 2nd & 3rd gears. They are different sizes, 1st, on the right of this picture, is the largest and is on the right. First drain the gearbox, you can see the drain plug in the bottom right of this picture. Then disconnect the air pipes. You can see the eight nuts you need to remove to remove the cylinder head. The pistons come out very easily, they are sprung and pushing them in will loosen them.



Clean up the cylinder head, pistons and springs. Remove all traces of the old gasket.



You can see the metal circlips that hold the piston seals in place. They are easily removed by opening them up with a screwdriver blade.



Here are the new piston seals in place. Check the cylinders for any damage before replacing them.


Replace the cylinder head and reconnect the air pipes. Donít forget the replace the drain plug before refilling the gearbox.


Please email me with any corrections and additions to this article.


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