Changing Diff Ratio's in the D1

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Originally Posted by roverv8

My problem is the other way,
My 94 Disco V8/auto is reving at 2600rpm @ 100kph (doesn't help my fuel bill)
most Disco's only sit on2200rpm @100kph

I don't know whether to blame the diff ratio or the tranfer case ratio,
Although im suss on the transfer case, it has a bit of a whine to it, like the gearing is higher

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A defender (1.41:1) t-case OR 4.11 diffs will both give you ~2600 rpm at 100 km/h in high range.

However your low range will be the same as standard if you have a 1.41 t-case.

It is easy to jack up a wheel and check the diff ratio.

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It is easy to jack up a wheel and check the diff ratio.

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What do i do, thanks in advance

[quote=roverv8;1456129]

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It is easy to jack up a wheel and check the diff ratio.

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What do i do, thanks in advance

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Jack up a wheel (on flat ground with handbrake off and out of gear with CDL disengaged).

Turn the prop and count the number of revolutions required for one turn of the wheel (or vice versa - the wheel is easier to turn).

Your diff ratio is halved if you just turn one wheel. So 4.11 will be 2.055 turns of the prop for every turn of the wheel. 3.54 will be 1.77.

I used 4.11 on my D1 and found it quite acceptable on the road with 285 x 85 x 16's which work out to be almost 33's and good off road.

Of course I was also able to go up to 35's quite comfortably with that ratio as well which was also helped by a 4.6 under the hood.

But the nicest modded car i drove was a rangie on 35's, standard ratio's and a stinkin hot 4.6 under the hood. Now that was sweet on and off the road but would put you back to looking for crawler gears for extreme low range work where you want to use engine breaking and go slower

Established the car has 4.37 diffs. I let it go..too much stuffing about for what I want.