Jeff McNeal wrote:
>
> I've put about 75 miles on the car which has a D-type O/D, which was "rebuilt"
> by the PO. When I filled the gearbox, I used regular 90w hypoid gear oil. I
> had the car on jackstands so the front and rear of the car were level with the
> ground, and let the excess oil drain out of the filler hole before inserting
> the plug. The O/D takes a second or two to engage, but disengaged instantly.
> I seem to recall this as being SOP. So far so good. But on my drive home
> this afternoon, the O/D started vibrating the drivetrain when engaging and
> didn't feel like it was engaging fully, drifting in and out of operation
> insofar as I could tell by the tach needle and engine sound. The engine RPM
> when engaging the O/D was maybe only 3000 or less. Could this be the problem?
> Should I top up the fluid again? What's going on here? Anybody? The
> inhibitor switch is working correctly, so I don't think I could have already
> damaged the thing, but I'm admittedly a little concerned. TIA
>
> Jeff
Jeff,
I can't say about your overdrive problem but I will make the following
comments.
1. Because of the brass parts in your transmission, you want to make
sure that the gear oil does not have any sulfur in it. This will cause
the brass parts to wear prematurely and become gold sparkles in your oil
when you drain it. But don't replace the gear oil with synthetic
either. Today's synthetic lubricants are too slippery to allow the
synchronizers to grasp the gear cones and allow smooth shifting. I have
discovered that Redline MTL works well even though it is synthetic. It
has some magic additive that allows enough friction to make the synchros
grab quickly.
2. If you drain the gearbox, measure the amount of oil that comes out
and compare that to the recommended quantity in the manual (2.85 US
pints). I bet you will find that you have added a bit more than that if
you filled it to overflow. I discovered this quite by accident and in
thinking about it, I figure that is the reason why most Spitfires leak
gear oil out the front bearing.
Cheers,
Joe
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