Thread: diff centre

There are a few fine spline diffs out there. I am not a guru on them all but I'll try.

I will list them in order of strength and spec, which virtually follows age as well....


1. The fine splines as I understand came out in Late classic rangies. Maybe as early as 1990?? These diffs are identical front and rear and the banjos can be swapped. They are spiral bevel cut. To suit strength whilst running in the rear, and the crown wheel and pinion are therefore running 'weaker' reverse direction when fitted to the front. This is not too much of an issue because the rear is usually the heavily loaded end, by bothe weight and drive. I believe all aussie disco 1s got these diffs front and rear. And the fine spline defenders run these in the front. These diffs have two side gears in the centre. My experience says these diffs are fairly reliable up to 31s with a mild v8 or 300tdi
Isuzu county owners or radical v8s can kill them pretty easy. Anything over 31 dramatically takes life out of them too

2. Then you have 4 side gear diffs of similar construction, these diffs can be found in the p38 rangie and disco 2 i believe . They are also the diff now run in the rear of the pumas. These diffs are also ok up to certain tyre size. The crownwheel is generally the weak point on these diffs. Not sure if these will bolt into earlier classic housings but I think they do. The important upgrade with some of these diffs is that the direction of the spiral bevel cut is reversed for the front diffs. This is definately the case for HSE p38 rangies. These diffs are specific to one end or the other. Fit a front to the rear and it will be much weaker.

So the utimate fine spline banjo combination would be disco 2 four side gear centres with reverse cut front crown and pinion and conventional cut rear crown and pinion. I would then get these diffs pegged. A process where a button of bronze or similar material is machined in on a steel peg on the back of the drive load area of the crown wheel. Its not really how much horsepower or tyre size will these handle, but what is the driving style of the driver?? But this diff combo should last quite well with 33s and a fair bit of abuse.

There are also aftermarket upgrade crown and pinion available and difflocks that actually increase strength....

Hope some of that helps

There a few things to know about the transfercases. If you have and LT230 then they are strong reliable and readily available.

To Id yours, if you get under the vehicle and look a the back of the transfercase so you are looking at the rear tailshaft handbrake drum. Then look up and diagonally to the passengers side, the back of the transfercase should have a disc cover plate held on by a PCD type bolt pattern. This disc is about 6 inch round in the old speak from memory. It also lines up with the input shaft/ output shaf of gearbox.
The LT230 transfercases also have a filler bung about half way between the the hand brake drum and this disc. It should be a female half inch square. The serial number is usually located just near this filler bung also.

The other type of transfer you could have in a classic is a borg warner chain drive, this will look dramatically different and has a viscous diff lock so you will not have a diff lock select in the cabin.

LT230 transfers select high low and the diff lock on one lever, fore aft does the hi low, and side to side does the diff lock.

There are two types the LT230R(roller bearing earlier type)

An the LT230T (taper roller later type)

Most out there are LT230T these days and the T is an upgrade BUT I would not be worried about having either because they are both strong and reliable.

To id yours if you look at the back of the transfer again and look up above the filler bung about half way between the hand brake drum and the cover plate mentioned before you should see the end of the intermediate shaft. If this shaft has a nut on it and a washer with a rotary lock bolt tab under the nut then it is an LT230T as this nut preloads the taper rollers.


If the shaft has a big round head on it with a female drive in the end of it, then its an LT230R and has plain rollers.

The other thing you need to know is the ratios available.

classic rangies are the tallest at one just overdrive .99/ 1 or something
and the other just underdrive 1.1/1 ?? or very close

Then you have disco series one at 1.22/ 1 underdrive

Then you have defenders at 1.43/1

All these will bolt into your vehicle but the ratios will make a difference.

I find the disco ration is best behind a v8 in a rangie if you run 31 inch tyres or more. Highway cruising is maximised with the high ratio rangie tranfers though.

Lastly you have the Disco series two transfers, these are quite a bit stronger in the centre diff, with different cross shafts. The ratios in these a 1.22/1 also. You have to be carefull though coz some disco 2s did not get centre diff lock.


The ultimate LT230 would be an LT230T out of a series 2 disco With centre diff lock.

You can get aftermarket cross shafts to upgrade earlier transfers through Ashcroft and other aftermarket suppliers.

having said all this there is a really good section on iding these transfers through serial number on the tech section of this forum, just search LT230 and it should come up.

Good luck,
Dan