Eaton Detroit Locker 3.54 and Numerically Lower - what does that mean?

[twr7cx]

I'm looking to purchase and fit an Eaton Detroit Locker (replacing an Ashcroft Transmissions ATB) for the rear of my Discovery 2 (24 spline Rover type diff). Having researched the three part numbers (Eaton 187SL173A, Harrop 63-187SL-173A and Britpart DA5700) overseas and locally, I'm looking to purchase from VPW (Victorian Performance Warehouse) as their pricing is the best < Differential, Detroit Locker, 24-Spline, Land Rover, 3.54:1 and Numerically Lower, Each - EATON (https://www.vpw.com.au/differential-detroit-locker-24-spline-land-rover-3) > but noticed that they, like a number of the other retailers have a note of "3.54:1 and Numerically Lower" on the listing. Anyone able to advise what this means?

Is it referring to the diff gears fitted with it? I run Ashcroft Transmission 4.12 Heavy Duty R & P < https://www.ashcroft-transmissions.co.uk/ring-pinions/heavy-duty-4-12-r-p.html > so would this combination therefore not be compatible together?

The Eaton catalogue < https://www.eaton.com/content/dam/eaton/products/differentials-traction-control/eaton-performance-differential-application-guide-en.pdf > offers:

https://i.ibb.co/c8N44WW/Screen-Shot-2019-12-29-at-2-15-51-pm.png (https://ibb.co/c8N44WW) https://i.ibb.co/mNCSpSQ/Screen-Shot-2019-12-29-at-2-16-25-pm.png (https://ibb.co/mNCSpSQ)

[Tombie]

Why I cannot answer.

Numerically lower would mean 3.54 or less.
Based on that 4.12s would be a no.

Again, I don’t know why. Although hazarding a guess - CW flange spacing most likely.

[PhilipA]

I think they mean the other way.
As you get lower in ratio the pinion gear gets bigger (more teeth) and the crown wheel has to be further away from the pinion centre line.

At some point the crown wheel will become too thin and the diff centre has to be modified /different to allow for the crown wheel to be further away from the pinion centre line.
I am pretty sure as I refreshed on google eg 4.11 =37 crown wheel 9 pinion. 3.70 =37 crown wheel and 10 pinion.

Regards PhilipA

[twr7cx]

Numerically lower would mean 3.54 or less.
Based on that 4.12s would be a no.

Again, I don’t know why. Although hazarding a guess - CW flange spacing most likely.

Which pretty much means that their product is unlikely to be suitable for any serious off road builds as most would have looked to regear to suit the enlarged tyres. Disappointing.



I think they mean the other way.

If my understanding is right, 4.12 is a lower diff ratio than the factory 3.45 ratio, but, the descriptor says numerically lower so I would therefore they mean 3.45 and numbers smaller.

[goingbush]

The Ashcroft 4.12 R&P (and also Ashcroft 4.75 which I use) is a direct replacement for 3.54 Rover type ,(not P38) no spacer ring needed so maintains the 3.54 offset and it will fit the carrier meant for 3.54 .

[Ancient Mariner]

It must be a LR thing as of the 15 ford 9"ratios from 2.75 to 6.5 all take the same unit with the difference being axle spline count 28. 31 or 35 and side bearing size

AM

[Red90]

All aftermarket ring gears fit in place of the 3.54. The only thing that won’t fit is a genuine 4.7 used on Series trucks.

[mikek]

All aftermarket ring gears fit in place of the 3.54. The only thing that won’t fit is a genuine 4.7 used on Series trucks.


Whats the difference between the two, and I would assume an earlier rover car diff is the same as a std 4.7?