Diff ratio

Post by **Onne** » Wed Feb 23, 2005 6:46 pm

Does anyone know what ratio the diff on my car is: the numbers are as following:
P4 on t'other side MOWOG
ATA7033-5
Are these the correct numbers? if not where can I find them? I found these on top of the diff, on both LHS and RHS

Post by **ianselva** » Wed Feb 23, 2005 7:36 pm

They are stamped on the crown wheel and should also be on the casing in the centre and probably are 9/41 or similar format

Post by **Willie** » Wed Feb 23, 2005 7:59 pm

ONNE....have no record of ATA7033-5, suggest you use the method
I suggested earlier to check your diff ratio.

Post by **Onne** » Wed Feb 23, 2005 10:23 pm

Right, I will go for a ten mile journey, and I'll get a mate of mine to drive ahead of me for exactly 16,09 km. What sort of number SHOULD be there?

Post by **Stig** » Thu Feb 24, 2005 8:15 am

You could always compare the wheel revolutions with engine revolutions by jacking up one rear wheel (to double the wheel revs due to the diff) and turning the engine over a few times with the starting handle -take the plugs out and it's not that much effort.
That'll tell you the diff ratio, but if it's odometer accuracy that you really want to know then the road trip sounds like a good plan -assuming your mate's car reads accurately...

Post by **57traveller** » Thu Feb 24, 2005 9:59 am

Onne wrote:Right, I will go for a ten mile journey, and I'll get a mate of mine to drive ahead of me for exactly 16,09 km. What sort of number SHOULD be there?

Onne - I suggested that but only to check that your speedo was calibrated correctly. Use Willie's method of propshaft/rear wheel turns for determining diff. ratio.

Post by **Cam** » Thu Feb 24, 2005 10:08 am

Stig28 wrote:You could always compare the wheel revolutions with engine revolutions by jacking up one rear wheel (to double the wheel revs due to the diff) and turning the engine over a few times with the starting handle -take the plugs out and it's not that much effort.
That'll tell you the diff ratio, but if it's odometer accuracy that you really want to know then the road trip sounds like a good plan -assuming your mate's car reads accurately...

You don't need to use the engine. Just put the car in neutral and turn the wheel while watching the propshaft (after you have marked it with chalk or something). If you let us know how many turns of the propshaft occur per number of turns of the wheel then we can work out your diff ratio.

Post by **Stig** » Thu Feb 24, 2005 10:59 am

Cam wrote: You don't need to use the engine. Just put the car in neutral and turn the wheel while watching the propshaft (after you have marked it with chalk or something). If you let us know how many turns of the propshaft occur per number of turns of the wheel then we can work out your diff ratio.

Der, of course you don't need to use the engine. Sorry, I guess I was thinking overall gearing ratio rather than just diff. Brain's warmed up now.

Post by **Cam** » Thu Feb 24, 2005 5:02 pm

Ok. Using the following method:

One wheel jacked up off the ground. The other wheel on the ground and the propshaft marked. You should observe the following:

41 turns of the prop = 18 turns of the wheel = 4.55 diff
37 turns of the prop = 14 turns of the wheel = 5.286 diff
43 turns of the prop = 16 turns of the wheel = 5.375 diff
38 turns of the prop = 18 turns of the wheel = 4.22 diff

Those figures correspond to COMPLETE revolutions of the wheel & propshaft and are calculated using the crownwheel & pinion ratio.