MT75 gearbox + DOHC engine mounting

[Matthew]

Hi

I've just fitted the gearbox mount for my MT75 gearbox, and the output shaft has ended up about 25mm higher than the input to the diff. Will much difference be OK?

If I really had to I could drop the mount down a bit, but the bottom of the main part of the box already sticks out about 15mm below the chassis rail and I'm not keen on putting it any closer to the ground.

Matt

[twinturbo]

What joints are you using?

Idealy you want it in line if possible.

TT

[Matthew]

Hi TT

I don't have the propshaft yet so the joints are still TBD, but I was looking at the Westfield type with the rubber doughnut at the front - not sure if that has a UJ at both ends or not. The other possibility is to go for something like Dax use in the Rush which I don't think uses the doughnut.

Just worked out the angle of misalignment - about 1.8deg

Matt

[silvertail]

Hi Matt,

I'm working on a DOHC/MT 75 build as well, just haven't got as far as you yet.

If you're having the propshaft made up by a specialist, I'd contact them and ask about it - no harm in letting the professionals explain it! Alternatively, I think "axle" on this forum has already completed his DOHC car - maybe he can explain how he did it?

Regards, Mike.


For a bit more help/info though:

1) This question has been raised on Locostbuilders a few times, with no real conclusions! A lot of the threads refer to this webpage.

Scroll to the bottom of the page, and you'll see what limits the page's author puts on the propshaft angles. However the working angle limit of 4 degrees only covers a max. of 3500rpm; the DOHC engine at full whack in 5th gear can be doing almost twice that!

3) Don't forget to consider lateral offset of the propshaft as well. If you're looking directly down on the car, you want the engine and diff to be (almost) perfectly in line (if that's possible). Otherwise, the propshaft angle will be greater than you've calculated.

[twinturbo]

Could you move the diff and angle it so it's in line?

TT

[teun]

Hi i use a 2.3L dohc engine with a MT75 gearbox. I do have the propshaft in line. The problem is i do not know how to place a picture