RR diffs into series 3

I have got a series 3 lightweight with a 2.5 n/a diesel fitted by the previous owner, as such it is very low geared and I have decided that the most cost effective way to remedy this is to fit RR diffs. Does anybody know of any pitfalls to watch out for?

ey oop mikey love, hows pauline, any road, the only pitfall is yer have ter be careful not ter drop em on yer when yer fittin em, otherwise, great iea. they do make the gearing a lot higher though, some folk recon too high, but i spose its down to personal preference, cheers

Hi Mickey love. The RR diffs will go in no prob. 1 thing you might want to try. Fit the rear one first. easier than the front. then take off front prop and take it for a drive. see if you like how it goes. if you do, then go to the effort of fitting the front one.

got them fitted in my series petrol nice top end with 750,s on. can cruise at a nice 50 without all the thrashin and as been known to actually venture into the fast lane down the m5 to overtake normal motors. only drawbacks i can find is hills can make ya change down earlier than expected and the speedos out about 5mph for every 10 mph,so 20 mph on the speedo is actually around 30,30 mph on the speedo is around 45mph and so on.
cheaper than an overdrive though

I put some in my Lightweight fitted with skinny tyres n rims and with OD its given a 10mph increase top end.
The oil filler for the rear diff on the LW has the level plug in it. You will have to either drain the axle and fill it with the new diff fitted through the air vent or modify the case. If you fill it via the vent warm up the EP90 to make it flow easier...

SA Landy Man said:

Hi Mickey love. The RR diffs will go in no prob. 1 thing you might want to try. Fit the rear one first. easier than the front. then take off front prop and take it for a drive. see if you like how it goes. if you do, then go to the effort of fitting the front one.

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why would ye want to take the front prop off just test the rear out??

Agree with fit the rear first for A TEST DRIVE, It should increase top end by 05 to 010 mph, standard are 4.7 :1 RR are 3.54:1 make sure they are the older RR difs due to the splines being different on the later models, splines the half shafts fit into.

ye pal make sure u get early RR 10 spline diffs. Im upgradin mine in a few week on my 2.5 series 3 as my landi is far to loud and only tops out at 55mph. Good idea to change the rear first and give it a test as long as u have free wheeling hubs on the front axle.

Why do you need FWH to prove the motor will pull the higher gearing? Just don't engage 4wd until both diffs match!

The only drawbacks to fitting them are minor:1, your speedo will be way off, 2, Your low range in the transfer box will also be a little higher.
I have a matched set if you need them. Was going to put them in my series three, but, I decided to go with the Ashcroft High Range transfer box instead. I wanted to keep the lower low range for the mud and weeds.

If the RR diffs are too high you can get other ratios i.e. 4.3 and 4.1 from rover cars eg rover 80 , etc (if you can find a pair).

Sorry to ask here too, but the RR diffs, are they 10 spline that go in Series?

Series Noob here!

metallicachick86 said:

Sorry to ask here too, but the RR diffs, are they 10 spline that go in Series?

Series Noob here!

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yes or early 200 discos, you will have to create an oil filler hole in the diff pan as series have the filler plug on the diff casting

You could change the sun gears in the diff to the splines you want

Sounds like fun. Guess its cheaper than an overdrive if it gets similar results.

So you make your own oil filler hole. does this have to be in same place as RR one (presuming its same place as disco). Sounds stupid but could i just drill a hole in the pan, then push a slightly bigger bolt into it, to force the thread, with a rubber washer? (really, a noob, never guessed!)

Toms not bad at mechanicing but some stuff is a grey area still!

The Diffs I have are 10 spline out of a 1988 RRC

I put them in last weekend and they have made a real difference. It was easy to do and I would recommend it to anyone thinking of doing it to theirs. Big thanks to all who replied.