diff ratios

[JohnF]

When we do the swap of a 4BD1 + Isuzu 5 speed gearbox into the 1991 3.9 V8 Range Rover, will we need to change diff ratios. If so will the diffs from a 300TDI disco wreck [that we are wrecking] be suitable for the Range Rover??? Thanks guys.

[BigJon]

Same ratio, no benefit to be had.

[Distortion]

diff ratios should be the same

I ran into issues with the Trailing arm brackets when installing a disc to disco RRC diff into my 300tdi so you might have issues going the other way but this will depend on the year of the RRC

http://www.aulro.com/afvb/technical-chatter/137771-maxi-drive-locker-install.html

The above thread has some photos from my install

The above won't matter if you are only doing centres but remember there would be axle and I believe cv changes if you go down that path

[Ancient Mariner]

Ashcroft Transmission Ratio site is a excellent source for any ratio questions

AM

[lokka]

Only difference if you swap out the whole housings and arms is the size of the pin in the rear bushes in the chassis

If it was me I would use the arms and bushes front and rear from the disco into the rangie even the A frame in the rear swap it for the disco one or at least the ball joint if its in better condition

Next step is that you will need to run a taller tyre like a 235x85x16 or similar to get the best out of having the isuzu as the 33 inch size tyre works best with the motor ratio combo :D

[Dougal]

Higher ratio lt230 works best.

[Vern]

Combination of both I think, 1.003 transcase and at least a 33" Tyre works very well together

[justinc]

Combination of both I think, 1.003 transcase and at least a 33" Tyre works very well together

...only with a turbo....:cool:


jc

[Vern]

How could anyone in their right mind live without one:D

[Ancient Mariner]

AS the time is getting closer any one want to polish up the crystal ball with a prediction 3.0 diffs 1.003 TC and 32" tyres MXA 5r):)

[Vern]

Should be fine AM, particularly with the msa ratios. If not, you know where the fuel screw is:)

[justinc]

yup, your 4HE1T torque curve should be very happy...:)


jc

[landrover dave]

AS the time is getting closer any one want to polish up the crystal ball with a prediction 3.0 diffs 1.003 TC and 32" tyres MXA 5r):)
Don't forget when you change diff ratios you not only effect high range, but low range as well.
Also 235/85x16 are nominally 32", 255/85x16 are 33.1", 285/75x16 are 32.8".
Be careful when playing with ratios, as you might end up with your rev range too low at cruising speed. I think with std diffs and your gearbox ratio choice will be right in the sweet spot. The 4bd1 has its sweet spot at around the 2500rpm mark.

[lokka]

...only with a turbo....:cool:


jc

Mine was great with no turbo and 285x75x16 and the LT95 it was no rocket but it was good to drive

Will be better soon I have it on the work pad now and a nice LT95A on the way as well as the turbo gear sitting in the shed :D