Just about to re-do my gearbox mount for the 10th time and i realised something. My gearbox is pointing upwards at a slight angle (engine end higher than prop shaft).

Now i apprecate when the car is moving up and down hills the gearbox will change angle but ...... is it good practice to have it level?

(the correct answer is no here as i'll have about 4.5" of ground clearance and my exhaust will fit nicely)

Nope, its more important that the drivetrain components are all parallel with each other, for example the engine/gearbox, propshaft and Differential should all be parallel thought whether this is horizontal/level or not is not critical....Obviously the closer to level the better cos it will give an even distribution of oil but if it don't fit it don't matter too much.....Cheers Oli.

errm, i'd disagree with that a little, the gearbox should not be inline with the diff, this will mean the UJ's aren't taking any forces in the same place all the time as the joint will move slowly as it turns.

(i know thats a terrible description, i've had a drink and it makes sense to me! :p)

Ideally the prop shaft mounting flanges on the diff and gearbox (no flange on type nine ) should be paralell although it's not neccessary they are at the same level /in line . Suspect with the type nine the diff flange should be at 90 degrees to the output shaft on the gearbox Explained in issue 7 of PPC

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Originally posted by MikeR
errm, i'd disagree with that a little, the gearbox should not be inline with the diff, this will mean the UJ's aren't taking any forces in the same place all the time as the joint will move slowly as it turns.

(i know thats a terrible description, i've had a drink and it makes sense to me! :p)

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i thats the case, the only way to get them parallel is to have the engine and gearbox level as the diff axle brackets are set at 90 degrees to the input face.

to quote myself when i hit another brick wall...........

Bugger! Bugger! Bugger! Bugger! Bugger! Bugger! Bugger! Bugger! Bugger! Bugger!

and

Bugger!

Would it be any easier to lower the engine mounts? that would have the effect of lifting the rear of the gearbox.

yeah - just trying to get max ground clearance for touring .......

got the engine almost level with the bottom chassis rail at the moment!

Going to end up lowering everything!

Can the sump be shortened ? the lowest point on the bell housing may be the best point of reference?

It is "normal" to have the rear of the chassis sitting slightly higher than the front -- has small advantages to do with aerodynamic drag and stability.

The reason why the gearbox flange and diff flange should be parallel, is to ensure that the variations in propshaft speed introduced by the first UJ are canceled out perfectly by the second. If this doesn't happen then you get vibration.

However, IIRC then the cancelation still happens even if the angle of the second UJ is equal but opposite, i.e. as long as the total angle is shared evenly between the two joints (and the angle is in the same plane) then it should be fine.