Do I have the correct diff?

Hi Guys, looking for some opinions I rescently bought a used assembled locking arb 10 spline diff, to put in my 200tdi. The guy said he had used it on a RRC so it would fit straight onto my disco no worries. Well I took mine off mounted this one, set the locker up, all worked fine. No noticeable change of speed, funny noises ect just seams to run like the other one..... I'm not a diff expert but I did notice the casing was a bit different to mine. It had an extra bolt/oil plug mounted at the oil level mark, on the right of the diff casing. I have researched this a bit and it seams more common on series LR's. This concerns me as series LR's use 4.7 rather then 3.54 ratio on the later coils sprung rovers. Is there anyway I can check if its the correct ratio, would I notice when driving it? Wouldnt the speeds differ between axles causing premature wear of the cd? and peculier handling?? If it drives fine, do I have nothing to worry about and just presume even though its built in an early diff casing that the ratio is correct? Whats your opinions ow wise ones, thanks in advance Jim

Hope there the same, got a RRC diff in my disco lol

if your worried jack up the back axle both wheels as its a detroit you may need a friend to help you and turn themboth then count the revoloutions should be 3.54 so 3 and a half turns of the propshaft to one turn of your rear wheels. If the propshaft turns 4.7 nearly 5 times then its a series ratio.

I suspect its beem built into an early casing and you have nothing to worry about.

Mark all RRC Disco Defenders coil sprung have the same ratio of 3.54:1 unless it was a special

i run 4.7's on my 90 and a higher ratio transfer box.

Thanks allot for the suggestion Jai I will check that to mo.

I presume If you change taio's you must change on both axles?

Cheers

yea, best to have the same lol

yep rear is a salisbury hd axle

I have those same Diffs in mine. They also have the early type 4 spline diff flange.

This was fitted to series 3 and early defenders.

I wish mine had 4.7 Diffs in now I have 33" tyres but nope it has the standard 3.54, they must have come out of an early defender.

Cheers

I think they my be Early RRC from the 70's with the extra filler bung probably left over stock from the series motors.

3.54 were never fitted to Series motors from the factory unless on a special. Early 90's 110's all had no filler bung in the diff casing by 1984/5 all axle casings had bungs in them I believe.

Mr noisey what engine you got?

It'll be early classic then.

I was meaning the diff casings were same as series 3, it's definitely got 3.54 Diffs.

Mines a 3.5 v8 dude, but the Diffs were bought with lockers in, out of another 3.5 disco, but they weren't from that either originally so full history unknown.

All I have managed is that they have 10 spline, extra filler hole and 4 spline pinion shaft, which I thought was early defender!

Cheers

Woulda thought a 3.5 disco with 1.2 tranny box would pull your ratios ok? TBH. might be worth you going for a defender 1.4 teanny box to help your highrange but low range your stuck with your ratios.

Did the test and yes you were right nothing to worry about, 3.5 turns so all good. Thanks allot for the advice Jai!

Mr noisy your running 10 splines have you found this to be ok with the big strong v8. I have the 10 spline locker on mine, would like to have got 24 but budget did not permit. Its not a trials vehicle anyway more for emergency use overlanding.

Am considering putting a defender transfer on mine. I am only running 32" but pretty sluggish in high range 1st, what will running a defender tranny do for my top speed, reduce it I presume? Wouldnt want to loose much more top end as it doesnt do much more then 70-80 now! Cheers J

No Problem. Happy to help.

You can use ashcroft transmissions ratio calculator to compare your current gearing to your proposed gearing.

www.ashcroft-transmissions.co.uk

My final setup is an lt77 to a 1.002:1 transfer box and 4.7 diffs running 36.5 measured tyres

Hello

I have had no problems with the 10 spline. The car gets worked hard with lots of wheel spin in anger, locked and unlocked. I only have MUDs though, I think I would have broken something with extreme tyres.

Ratio wise, it does pull just fine and I get nice low revs at cruising speed which is good for economy. The problem is I have a quicker than ideal 1st low ratio, I would like to crawl.

The easy option is underdrive with a section of floor cut and modded, or a high ratio transfer and low ratio diffs like you Jai.

As above, it's alright, just not ideal for low speed work. I would regret 4.7 diffs on the motorway unless I raised the transfer ratio!

Cheers