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Gearbox oil leak.

Ken Young

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I am starting to go crazy over a gearbox oil leak on my 1967 GT6.   I recently removed the box to fix a leak and that had started to develop and sure enough I found that the lip seal was damaged and in fact so hard it was almost like plastic.  I replaced and the copper washer on the lower bolt and the gasket as per the workshop manual.   After the fix, the leak was cured for one 12 mile trip.  However, it has started again and I am flummoxed.  

It looks like I am going to have to remove the box again whatever the reason but I was looking for anyone else with the same experience.  One thing I noticed during the last repair was that there was a small amount of play in the input shaft. It could rock around 1mm from side to side at its extremity. Is this normal? Also, the bearing to the shaft at the front of the box could slide out fairly freely from the gearbox?  Should it be an interference fit?   I am thinking that the rocking could make the shaft move around during accel and decel to make the input shaft run eccentric to the seal?



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1mm rock at the outer end of the input shaft is very good on one of these.  Often much more.

When it's fitted to the car, the other end of that shaft should be supported by the spigot bearing in the end of the crank.  This needs to be fitted and in good condition.

Does sound like your bearing is a bit of a loose fit in the casing, but they aren't that tight to begin with.  I doubt it is the cause, but you could use some bearing fit fluid on it I suppose.

Are you sure it's a gear oil leak and not engine oil?  If so you need to check that the gearbox breather is clear and also that there is no leak path between the steel nose piece (which houses the oil seal) and bell-housing casting itself.


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