Transfer box Ratios and economy

I've had both a Disco transfer box in the ninety and a ninety one, I found the disco one a little too high geared with my tall tyres.
I was wondering if anyone compared fuel consumption between boxes ?

I went from a 2.5na std transfer gearbox to a disco 200tdi and transfer box. It went from 24mpg to 32mpg

landowner said:

I've had both a Disco transfer box in the ninety and a ninety one, I found the disco one a little too high geared with my tall tyres.
I was wondering if anyone compared fuel consumption between boxes ?

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When I swapped them over I did not notice a difference in fuel economy with my 200tdi, But I did notice about an 8mph speed increase so started driving at 65-70 rather than 55-60. Had I remained driving at the slower speed I would have though I would have increased the mpg accordingly.
What engine, what tyres and what do you use the vheicle for to find the gearing too high? I run 265/75/16 with a 200tdi and have no problems with the gearing. Occasionally with a fully loaded 3.5t trailer I might need to slip the clutch a bit or start off in low box, but that is a small price to pay for the higher gearing. If this was its sole use however I would probably have stick with the defender box.

They are quite tall, in this picture you can see the difference against Disco tyres, the speed difference at around 50 was 5 mph. with the tall tyres and Disco transfer box I spent more time in fourth than fifth and on the motorway found myself changing down for hills as I usually run at 55 mph. , cant remember the size

landowner said:

They are quite tall, in this picture you can see the difference against Disco tyres, the speed difference at around 50 was 5 mph. with the tall tyres and Disco transfer box I spent more time in fourth than fifth and on the motorway found myself changing down for hills as I usually run at 55 mph.View attachment 163142 , cant remember the size

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Looking at the picture I would guess at 235/85. What engine are you running? That sounds like under power rather than over gearing (arguably the same thing). Unless you have a tdi or later I would not consider a disco box as it will not have the power to utilise the higher gearing.