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big steve

Member Since: 24 Dec 2009
Location: hertfordshire
Posts: 2456

2015 Defender 90 Puma 2.2 HT Montalcino Red

diff ratio ?

hi guys

any one know anything about this
im running 35 inch tyres what implications would it be to change my diff raios to 4.1 instead of standard 3.54 what benefits would there be

kind regards steve 2015 2.2 tdci hardtop xs
3.2 conversion DONE 238bhp and 707nm torque and thats just the start ;-P
hybrid turbo in build -done ready to fit
ashcroft atb in transfer box
6 speed auto in build

25th Jul 2011 7:30pm

nicknick

Member Since: 28 Feb 2011
Location: halifax
Posts: 30

2010 Defender 90 Puma 2.4 CSW Tonga Green

Hi Big Steve,

I am looking at this mod myself, but doing suspension lift , diff re-gear and 35" tyres all in one hit.
Going to 4.1 crown wheel and pinions should put the gearing back as near as dammit to standard.
plenty of grunt on hills as the revs/torque are back in the right place. also low box becomes low again,
engine braking is good again.
i did this to a 300tdi 90 quite a few years ago and i had learned to live with 35" tyres but re-gearing the diffs was money well spent as it was my daily driver too.

hope this helps

25th Jul 2011 8:39pm

diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6089

A few years back I did the same with my 90... i ran 35"s on it, so got some BGR (Great Basin Rovers) 4.1:1 CW&P's.

It made the gearing more or less back to standard feel, maybe ever so slighly under (as in, you were revving a bit harder to get the same speed...but not much)

It worked really well, but in the end i reverted back to standard gearing and standard tyre size, only because i got fed up with constantly tweeking the suspension/props/brakes to make the thing drivable as a daily driver.

26th Jul 2011 6:57am

LR90XS2011

Member Since: 05 Apr 2011
Location: bickenhill
Posts: 3639

2011 Defender 90 Puma 2.4 XS CSW Galway Green

Big Steve
take your sat nav speed for any number of revs in 5th gear (i assume 5th gear is 1:1) divide it by 4.1 and times it by current diff ratio 3.54 and that will give you the speed for the same revs in the same gear. (with a 4.1 diff) If you then draw a straight line on a graph from Zero to the point that corresponds with the speed and revs and on to your maximum revs you will know exactly how fast you are going compared to engine speed with the new diff in 5th Gear. You can then pick any point on the graph and draw the same lines for each of the other gears by dividing the result by each gear ratio. Hope that makes sense!

I used to race a mini marcos and would match the diff ratio to the intended use or cam profile in just the same way DEFENDER 90 TDCI XS,

I hope everyone is well and your land rovers make you happy

26th Jul 2011 5:43pm

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