yes will drop the revs alot! May be worth you while checking out Ashcroft transmissions website their gear ratio calculator to get an idea of engine revs vs speed. you can compare standard what you have now to any combination they supply or indeed 3.5:1 std rangerover ones. Remember that you need to have enough oomph to get to the theoretical speed quoted. Or maybe call ashcroft as they may have a better mid way setup 4.11:1 depending where you are based and cost of them building them into your diffs.

I've seen that some guys recommend just swopping the rear diff. How does this effect the vehicle in 4wd?

you cant use it in 4wd ,i said to try it like that as rear is fairly easy to do ,saves alot of work if doesnt suit you ,if you like it then fit front another day

JohnnyP said:

People Calm down!! I'm going to get a LR specialist to fit them if I decide that's the route I wish to take. All I wanted to know is that if by changing the diffs it would improve the road performance of my landy an drop the revs so I'm not putting so much strain on the gearbox.

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Trouble is, that's not an easy question to answer.

1. What is road performance? It might give you a better top speed if you can still pull the same engine rpms, however if your engine isn't great then you may find it sluggish with a lower top speed

2. Yes it'll drop the revs for a given speed, but as said, you'll need to the power to pull it. Think of it like a push bike, the cogs next to the pedals. Going to 3.54:1 diffs is like going from the middle front cog to the large one. You'll go quicker, but it'll make your legs work harder.

3. Strain on gearbox, well again yes, potentially lower revs, but it might actually be as much or more strain due to the affect of the gearing.


It's not a bad swap, but it's probably not the first thing I'd look at doing on a Series. I'd make sure other parts are working and running right first.

And the big question is, do you or will you use it off road in low range? If yes, then 3.54:1 diffs will affect this in a negative way.

Also (and apologies if you've answered already) what size tyres are you running. If you're on standard 205's, then swapping them to some 235/85's or some 7.50's would be worth while. However if you're already on a tall tyre, then 3.54:1 diffs really will affect off road crawl speed.

As for the 4wd part. Well in normal use a Series is RWD, so as a test you could just swap the rear diff and see how it goes in high range. But evidently you won't be able to see what low range is like as the front and rear wheels will want to spin at different speeds.

If you are doing this yourself, then it would certainly make sense, but less so if you are getting a garage to do the work.

I'd look into some overdrive units, they are more pricey, but possibly a better solution.

sorry if this has been mentioned already, but before any changing of diffs, try pulling off in 2nd gear instead of 1st. this will be close to the range rover diffs. if it copes, it should be a good upgrade. i have fitted rr diffs with 900-16 tyres on my 200 tdi series 3 88" (with 109 brakes and servo) and its far more useable. it will cruise at 75-80 on the motorway with ease (a good laugh passing disco's and rangies) and because of the diesel engine, it still has enough engine braking off road. i have had to ajust my speedo (with tip-ex marks) using a satnav and marking just below to be on the safe side. it gives an accurate-enough speed. i put small lines for 30-80mph on the face. easily removable and you get used to it quickly. i would recommend the swap if you have a 200 tdi but im not sure the 21/4 petrol would be up to it.

i fitted 33 inch tyres and it cured it hard revving at 60mph, had to modify the arches a bit tho

34/35 inch normal 900 size tyres on 3.5 diffs must be horrendus offroad. I have run 37 inch tyres on a defender and low range was a joke! 1st low was way too fast when decending anything half worthy to be off road. I guess being spoilt driving trial motors is to blame but honestly control no control even with the engine sat firmly at tickover it was too fast to be a pleasurable decent. Chaplegate and a some local relativly tame trialling had me swapping diffs to 4.7's because I refuse to be at a disadvantage offroad and it showed in my results.

but most people dont do what you do ,and 1 or 2 diffs is going to be cheaper than big wheels and tyres ,my ex light weight run better on 3.5s and still managed most things ,towing,laning in wales,trial motor wouldnt be much use to him if hes after getting to work etc

a good 2.25 would be a match for an average TDI. My old mans 109 used to cruise at 70mph Overdrive fitted. It was quiet and unlike a tdi it was very very smooth and offroad driving was a pleasure as the rpm could drop down to like 500rpm and still not bat an eyelid unlike a diesel. The engine was messed with skimmed head 40thou over sized pistons and from memory he removed a link from the carb so it never pumped fuel in when you hit the gas as a result he got great mpg travelling to and from Wales which we did every few weeks it suffered a slight hesitation when stomping the throttle which was easily driven around. 5he motor was 100 percent reliable regular oil changes every 500 miles molyslip everywhere and all mechanics were tip top.

Overdrive would be a good bet before diffs as said before. Probably as cheap or not an outragous cost if you get a good one vs a landy garage changing your diffs.

my point I was trying to make was like 300 has said is the answer is not straight forward the options are out and he has ALL the info to make an informed decision. Thats what I like now its his choice knowing most of the implications before doing the mods. isn't it fair we give all relevant info to help ourfellow landy owner

many of my fellow trial pals use their motors every day for the work commute. One drives his 88 into Finchley everyday in fact i saw him yesterday on the way home bombing down the M1 at a steady 65 stereo sounding out some destorted Manson coming from his sodden speakers. Don't believe he has an overdrive nor 3.5 diffs i think he's just running stock on 33 inch tyres. Max alrc tyre size. And he didn't cut his arches i don't believe.

you find a good over drive cheap ,fitting one diff £50 gives most of what most people want not a difficult job even for a novice ,2.25 petrol is allright ,thisty and no torque top end you cant do 70 head wind or up hill ,he could fit higher ratio transfer box but costs more harder to do and unlike diff not so easy to swap back if unsure it was right thing to do ,if he asked about trialing i would probably agree ,but series with 3.5 diffs have done some adventurous off roading

with my 900-16 tyres (35" tall ish) i have fitted to 8 spoke wheels with 56mm of offset. the only bodywork i have adjusted was the rear, shorter sections of sill by hand (a good yank outwards) and the tyres clear the bodywork with the occasional rubbing on the front wings when turning and articulating. the only problem i have found is that the rear bump stops need to be extended. these tyres coupled with the 3.5 diffs have proved fine for everything i have thrown at it off road. the engine braking down steep hills isnt as good as before but its better than any low comp rangie v8.

bigger wheels do to some extent reduce braking efficiency