Grinding noise when cruising

Defender768 · Oct 24, 2020

Hi Guy,
Hoping you might be able to help me out. I’ve recently replaced my front axle on my 300tdi 90 for a brand new mod surplus axle. I now have a grinding noise coming from the transfer box area when I take my foot off the throttle at about 55-60 that goes when I put my foot on the clutch or accelerate out of it. I have removed the front prop and the noise went so replaced the prop and it’s still there. Also when diff lock is engaged the front wheels are scrubbing and moving a lot slower than the rear wheels... not sure if linked
TIA

neilly · Oct 24, 2020

not sure, but what ratio are the diffs on a military axle?

Cheers

jamesmartin · Oct 24, 2020

jack one front wheel up and count number of prop rotations to get wheel to make one revolution

Defender768 · Oct 24, 2020

neilly said:
not sure, but what ratio are the diffs on a military axle?

Cheers

I’ve been thinking this, transfer box output flange does have a lot play in it also

neilly · Oct 24, 2020

and as @jamesmartin says , when you have done the front, then do the back and see if the numbers match?

Cheers

Defender768 · Oct 24, 2020

jamesmartin said:
jack one front wheel up and count number of prop rotations to get wheel to make one revolution

Thank you, what’s the normal ? Transfer box output does have quite a lot of play also

Defender768 · Oct 24, 2020

neilly said:
and as @jamesmartin says , when you have done the front, then do the back and see if the numbers match?

Cheers

Thank you

neilly · Oct 24, 2020

Defender768 said:
Thank you, what’s the normal ? Transfer box output does have quite a lot of play also

Iirc 3.54 is the normal ratio of prop flange turning to 1 wheel revolution. @jamesmartin can confirm.
If your tbox output bearing is knackered then that would be something to fix anyway, but check it is tight and the nut is to the correct torque.

this has some useful info for you.
https://www.ashcroft-transmissions.co.uk/calc/ratio_calc.html
Cheers

jamesmartin · Oct 24, 2020

Defender768 said:
Thank you, what’s the normal ? Transfer box output does have quite a lot of play also

standard diff for a defender is 3,5 so if you have one wheel up the other wheel will go twice as fast so a 3.54 diff should take 1 and 3/4 turns, some military run 4.7 diffs so that would require 2 and 1/3 turns of prop

Defender768 · Oct 24, 2020

neilly said:
Iirc 3.54 is the normal ratio of prop flange turning to 1 wheel revolution. @jamesmartin can confirm.
If your tbox output bearing is knackered then that would be something to fix anyway, but check it is tight and the nut is to the correct torque.

this has some useful info for you.
https://www.ashcroft-transmissions.co.uk/calc/ratio_calc.html
Cheers

Thankyou guys

Grinding noise when cruising

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