Thread: Reverse Cut Ring & Pinion / aka High Pinion - front Rover diff

Ok so really the gears 4.10, 4.11, 4.12, 4.14 aren't interchangeable as stated by GBR based on that... i thought i made it clear when i bought them they were for the same vehicle and nothing was mentioned... HMMM!

Anyone know where i can source a 4.11 in Sydney that might have stock? I know LRA has the Ashcroft 4.12 (again, not interchangeable?), but i'm a bit pressed for the delivery time frame. Nobody makes a 4.12 Sals R&P as far as i know?

Get it in writing if you do fit them that GBR state it's ok...

I would be fitting a 4.11 reverse cut up front...

4.11 and 4.12 would be ok.
4.11 and 4.14 would stretch the friendship with your CDL

Fair call indeed... i shot off an email to GBR to confirm... i'll post back later what the outcome is

Originally Posted by GoldCloverLeaf

Ok so really the gears 4.10, 4.11, 4.12, 4.14 aren't interchangeable as stated by GBR based on that... i thought i made it clear when i bought them they were for the same vehicle and nothing was mentioned... HMMM!

Anyone know where i can source a 4.11 in Sydney that might have stock? I know LRA has the Ashcroft 4.12 (again, not interchangeable?), but i'm a bit pressed for the delivery time frame. Nobody makes a 4.12 Sals R&P as far as i know?

I have one set of ashcroft 4.11 new gears for a rover diff

Originally Posted by GoldCloverLeaf

OK... thanks for the input, but could someone please explain why this is the case?

If both ring and pinions cover the same distance in rotation over a different quantity of teeth, why does this pose a problem?

The ratios are slightly different - which means that the front and rear prop shafts will not be turning at the same speed on average. Whether it is a problem or not depends on whether the speeds are is "close enough". The "problems" that may arise will be those associated with excessive wear on the centre diff - the bits that will be rotating relative to each other due to the speed difference are plain bearings. There may be also more windup when the centre diff lock is engaged as well, but this can be a problem anyway when the centre diff is locked on hard surfaces.

A separate issue is that using different ratios front and back will bias torque between front and back (the axle with the numerically larger ratio will have more torque).

However, while I have no experience of this with such close ratios, my feeling is that none of the "problems" will be more than those regularly encountered with different tyre wear between front and back.

John

.04 difference is 1.28 inches on a 32 inch tall tyre. I guess like running a 32 and 33.28.

Probably not ideal on a daily driver

Originally Posted by uninformed

.04 difference is 1.28 inches on a 32 inch tall tyre. I guess like running a 32 and 33.28.

Probably not ideal on a daily driver

Not on my calculator!

4.14/4.11 X 32 = 32.23. About a quarter of an inch. I do not think that would constitute a significant problem.

John