Military-Vehicles: [MV] RE: M8 Greyhound Gearbox

[MV] RE: M8 Greyhound Gearbox

Alan Bowes (
Tue, 14 Oct 1997 12:57:08 -0600

On Monday, October 13, 1997 1:38 AM, Douglas Greville
[] wrote:
> Alan
> Hope I am not being a nuisance but I have a query regarding the
> gearbox in my M8 Greyhound.
> In case you are not familiar with the vehicle, they use a JXD Hercules
> with a Ford (I think) WG-T95 box (or thats what the parts manual calls
> it). I believe it to be an adaptation of a fairly standard pre-war
> truck gearbox, in that the motor is mounted facing rearwards and it
> uses a remote, reverse pattern gear shift.
> Now for the problem - I find it almost impossible to do a 3rd to 2nd
> gear downshift. To the best of my knowledge the box is syncro except
> for 1st and reverse. Double clutching does not seem to make a
> difference. When the vehicle is stationary shifting from 3rd to 2nd
> feels just the same as the other gears. This would seem to indicate
> that the problem exists only under load?
> Could this be a synro cluster problem (according to the speedo the
> vehicle has only done about 1000 miles since military rebuild) maybe
> something has too little tolerance and may eventually wear in. Or
> is it a characteristic of the box or worse an indication of something
> wrong?
> Thanks
> Doug


I'm afraid I'm not familiar with the M8 gearbox, but I know that many
four-speed transmissions (especially older ones) only have synchronizers for
third and fourth (direct) gears. On most of these transmissions, the
first-second sliding gear has a set of internal engagement teeth that slide
over a small set of external engagement teeth on the second-speed gear.
Perhaps this is one of those??? If I could look at a diagram, I could tell
for sure.

If this does have a second-gear synchro, it is apparently not doing its job,
due to wear, misalignment, broken synchro ring, etc. A dragging clutch can
also be very hard on synchros. The third-to-second shift is usually harder
on synchronizers than a fourth-to-third shift, due to the relatively greater
rotational speed difference, though this can vary between models.

I'm sure that someone out there on the list can give you a better
M8-specific answer than I could.


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