disco rear diff on RRC

[Ronphos]

Blew my 86 RR rear diff on the weekend. Have found a complete 97 Disco rear axel as replacement. The dealer said it will slot straight into my RR. However I am a bit sceptical on the gear ratios. Can someone please advise me if this diff will do the job. My gear ratio is 3.54 (standard) which is the original factory diffs.

[Hobie18]

Are you talking about slotting the complete disco housing etc in, if so then the bolts that hold the brake calipers on are a different size. Can't comment on the other things although I believe the ratios are the same - other will confirm this though.

[Ronphos]

Are you talking about slotting the complete disco housing etc in, if so then the bolts that hold the brake calipers on are a different size. Can't comment on the other things although I believe the ratios are the same - other will confirm this though.

Hobie, I am talking about changing the whole axel from wheel to wheel. I was wondering if there will be any issues. I am advised the ration is 3.54 which matches, but can anyone see any other issues?

[garrycol]

I cannot comment on the entire axle housing going in but as far as the diff is concerned it should be the same ratio BUT your old diff will (if not modified) be a 10 spline diff where the disco one will be a 24 spline diff. Therefore that actual axles will be different as will the splines in the hubs.

Garry

[KiwiBacon]

I have 97 disco axles under my 85 classic.
You need to change the rotoflex coupling to a flange. Check the taper size on the upper ball joint also.

[Bush65]

Also if the disco hasn't had the flange conversion, you also need a spacer that goes between the flange and pinion bearing.

[Ronphos]

Thanks all for the great advice. Yes Kiwi, thanks to your advice I have asked the seller to change the rotoflex coupling to flange FOC. I might be wrong but the 10 / 24 spline should not matter as I am changing the entire Axel including hubs.

[Ronphos]

I have 97 disco axles under my 85 classic.
You need to change the rotoflex coupling to a flange. Check the taper size on the upper ball joint also.

Kiwibacon, how do you disco axels handle? Has it been a worthwhile mod? I am only changing the rear now as a necessity since ripping my stock apart. But If it works out and I get some more $$ then I will do the front axel as well. Maybe someone can advise which is the better Axel/diff for playing in the ruff.

[KiwiBacon]

I have 97 disco axles under my 85 classic.
You need to change the rotoflex coupling to a flange. Check the taper size on the upper ball joint also.

Kiwibacon, how do you disco axels handle? Has it been a worthwhile mod? I am only changing the rear now as a necessity since ripping my stock apart. But If it works out and I get some more $$ then I will do the front axel as well. Maybe someone can advise which is the better Axel/diff for playing in the ruff.

The new axles work fine. While driving the only noticable difference is less backlash. I went from RRC axles with around half a million km on them (340,000 on the speedo, but I know it has been wound back) to disco axles with 80,000km.

I was previously running a disco rear housing anyway due to the back axle crimping one end years ago. So on the rear I swapped over hubs/stubs/shafts and diff head. My donor truck also had a bent rear casing.
On the front it was a bolt-up, but I took the time to swap over my vented rotors, bigger brakes and I put the 3511 dual lipped oil seals in all the hubs too.

Radius arms changed width, best to get the radius arms from your donor vehicle too. You'll also want to change the end bush in your panhard rod as the bolt size changed from half inch (12.7mm) to 14mm.

[Bush65]

I have 97 disco axles under my 85 classic.
You need to change the rotoflex coupling to a flange. Check the taper size on the upper ball joint also.

Kiwibacon, how do you disco axels handle? Has it been a worthwhile mod? I am only changing the rear now as a necessity since ripping my stock apart. But If it works out and I get some more $$ then I will do the front axel as well. Maybe someone can advise which is the better Axel/diff for playing in the ruff.

AFAIK, 10 spline disco axle assemblies were the same as 10 spline rangie axle assemblies of the same year model. I'm not sure when (or if) 10 spline drive flanges changed from 3/8" UNF bolts to M10 bolts (as used with 24 spline axle flanges).

The pitch circle diameter for 3/8" bolts in the hubs/flanges is smaller than for M10 bolts and they don't interchange. You have to be careful of this when fitting 24 spline axles and use the special flanges in imperial hubs - Ashcroft and HTE (and probably jackmac) make appropriate flanges, but AFAIK rovertracks do not.

Very early rangie diffs had different carrier bearings and adjuster nuts - best avoided.

Early rangies had 6 bolt swivel balls - I don't know what year they changed or what was used in 10 spline discos. Later swivel balls have 7 bolts.

The wheel bearings in 24 spline hubs are closer together than in 10 spline hubs, so the stub shaft/spindles and stock axles are shorter. Wider spaced wheel bearings will provide better support, and should be better with wheels with less offset. Grease seals in 24 spline hubs are not as good as the oil seals in 10 spline hubs.

Cv's in 24 spline front axle assemblies are the weakest.

Front brake calipers from discos are not compatible with the dual brake circuit used in rangies - re-use rangie calipers. The threads for brake lines also changed from 3/8" to 10 mm, but I don't know what year (was before 84).

I prefer to keep the earlier diffs and fit after market axles, flanges and diff locks or tru-tracs.

Edit: at some stage the width of the radius arms was increased - so width inside the plates on front axles will be greater.

[KiwiBacon]

AFAIK, 10 spline disco axle assemblies were the same as 10 spline rangie axle assemblies of the same year model. I'm not sure when (or if) 10 spline drive flanges changed from 3/8" UNF bolts to M10 bolts (as used with 24 spline axle flanges).

The pitch circle diameter for 3/8" bolts in the hubs/flanges is smaller than for M10 bolts and they don't interchange. You have to be careful of this when fitting 24 spline axles and use the special flanges in imperial hubs - Ashcroft and HTE (and probably jackmac) make appropriate flanges, but AFAIK rovertracks do not.

AFAIK the change came with ABS. That was when the axle housings front and rear had to be redesigned to accomodate the sensors. I don't know the exact year break for this. Some later style metric axle assemblies were produced with 10 spline shafts, these are rare but I have seen photos. My axles are from a 97 disco, they are 24 spline, with ABS, had grease filled swivels but still have the drain plugs. The drain plugs were discontinued sometime later.
I have changed them to the 3511 dual lipped oil seals, oil lubricated wheel bearings, defender calipers and vented rotors.

I ran for years with a metric disco rear axle case (with M10 stub bolts) and 85 era stubs, diff and axles. The rear stubs bolted up fine so the PCD's do indeed match.
It was only recently (about two years ago) that my metric disco case got the matching disco diff head, axles and metric stubs.

[Bush65]

... The rear stubs bolted up fine so the PCD's do indeed match.
...

Stub axles/spindles match, it is the pitch circle and bolts that connect the drive flanges for the axles to the hubs that do not match. Drive flange item 16 and hub item 10 in following pic from 110 parts manual.

[KiwiBacon]

Stub axles/spindles match, it is the pitch circle and bolts that connect the drive flanges for the axles to the hubs that do not match. Drive flange item 16 and hub item 10 in following pic from 110 parts manual.

Yes certainly. I missed the "drive flange" in your earlier post.

[Ronphos]

Thanks to you all for your great advice. We did the axel exchange on Sunday starting at 11am and we were in the Glasshouse Mts by 4pm putting her thru some rough terrain. Not bad since we had no crane or trolley jack and had to rely on manpower.We did not have any real dramas. The Brake Calipers fit perfectly. The panhard rods slotted in nicely with a few taps with the mallet. I had 2" suspension lift and the coils holders and bolt holes lined up. The shocks fit in even better that on the RRC axel. The brake lines were transferred across and with a little convincing were secured nicely. The taper bolt for centre stabiliser fit nicely. When testing the new axel, I found that the backlash had reduced noticebly and the overall smoothness of the auto trans was improved. In summary, If anyone out there is thinking of installing a 97 Disco axel (rear now confirmed) into a 86 Range Rover Classic, it is a perfect fit !! As long as the gear ratio matches the front. Happy roving.... RRonphos

[Hobie18]

Its interesting that you found that the brake calipers fit perfectly, because when we fitted 94 disco diffs into my 90 rangie we discovered the bolts holding them on aren't actually the correct size. The bolts/bolt holes through the disco calipers are slightly larger in diameter and hence the threaded hole in the diff housings are also slightly larger.

I would check that the bolts are seated properly in the disco diff housing just in case, so that you don't have an accident should the caliper snap off.

The bloke who fitted mine thought at the time of fitting that they were fine. It was discovered about a week later that they weren't .