Thread: New Rangie; diff gears

The standard differential ratio is 3.54

4.11 is a common aftermarket gear.

If you want more stregnth yet again, Bill at GBR now does a 4.14 gear set that he claims is stronger again over the 4.11 he previously did.
The set landed will be approx $1000AUS dollars.

There are 4.7 gear sets available too.

The old 3 speed autos did take away from the driveability as they sap power big time!

I assume it has the LT230 transfer case for the TF auto. IIRC the high range ratio in these was used to compensate for lack of overdrive in the transmission.

Disco high range gears will increase your overall reduction, or for even more you could use defender high range gears (the difference between these was to compensate for larger tyre diameter in defender).

4.7:1 R&P for diff are pretty weak.

The transfer case gears in the Torque Flite were the highest in available and gave a cruise of about 2000RPM at 100Kmh.

If you fitted bigger tyres the gearing would change by say 12% for 33inch. The 308 should easily be able to push this.

You do not say what the tyres are that you intend to fit, But IMHO you should not need or want any lower gearing as the Torque converter will effectively give you 80:1 in low low now.

If you lower the gearing you will use even more fuel on the highway and I do not think gain much in low range.

So leave it, as the 3.54 pinion and crown is still stronger than any 4 or lower diffs, except for the 2 planetary issues, and these are fixed with a ARB or maxi if you can find one.

Regards Philip A

So how strong are GBR 4.14s has any one got them in????????

3.54:1 has 46 teeth on wheel and 13 on pinion
4.1:1 has 41 teeth on wheel and 10 on pinion
4.11 has 37 teeth on wheel and 9 on pinion

As ratio increases, the pinion diameter gets smaller and the tooth load increases for the same transmitted torque. So teeth have to be larger to increase strength.

The difference in tooth load between 4.1:1 and 4.11:1 is small, but the teeth are larger for 4.11:1, thus stronger.

I don't know the tooth count for 4.7:1 sets, but would guess 47 and 10. They are renowned for being weak.

I guess 4.14:1 would have 29 teeth on wheel and 7 on pinion (I can't figure any other combination that would be reasonable).

So the teeth would be larger, but 7 is getting close to the point where you shouldn't go any fewer because the strength is reducing due to the tooth profile shape (thinning near the root where bending stress is highest and a stress concentration occurs in the fillet).

Edit: it looks like 4.7:1 has 66 teeth on wheel and 14 on pinion for 4.71:1 reduction.

So then if you were going to buy a set of 4.11 or there abouts who makes the best set

I bought the 4.11:1 ring and pinions for my disc from Ashcroft in the UK. I would recommend them, but have no experience with others.

Originally Posted by Mule

I'd like to look into is getting a higher ratio of diff gearing. I know it's quite low at the moment probly around 1:2.5ish, now I'm looking to increase it to about 4.5 or 4.9ish.

Just to clarify, 2.5:1 would be a high ratio diff and 4.5:1 or 4.9:1 are low ratios.

As pointed out above, the standard ratio is 3.54:1 which is common across all Discos and Rangies from 1970 until the mid-2000s. I'm not sure about the latest cars.