Land Rover Gear Ratios

Hi all hope somebody knows weather this set up will work or will the ratios be too low in top gear to work,
Its my old series 3 109 currently undergoing restoration/rebuild what I've broke on it number 2.

A few years ago i did a 200tdi transplant into it and it went well, but a bit too revvy, so i fitted a stage 1 V8 rear axle and range rover front diff so 3.54 ratio with series 3 gearbox and transfer box, kept off roading and decided i needed bigger tyres so fitted 255/85/16 well you can guess what happened next and bang goodbye gearbox. it lasted well and i knew i was asking a lot of it.

so this time i want to fit a R380 with series transfer box from ash crofts and I've done some calculations and the best i can get it too pull in 5th is 2404 does anyone know if this is too low and will struggle to pull this.

to run through the above clearly it is 200tdi + R380 +series 3 transfer box + 3.54 diffs + 255 85 16 tyres will it work or not.

Everyone likes pictures so heres she is

I think from my experience you will be fine.

This will depend on a few things IMO.

This is a stock Disco running 3.54:1 diffs, stock 1.22 transfer box and 33" tall tyres.


I've used this setup. It works ok, but will blunt on road performance, although cruises quite well. You won't use 4th until 40mph and 5th is useless below 50mph.

A stock Tdi will struggle, you'll really want a tweaked one (injector pump and/or big intercooler and more boost).

Your setup appears to give similar numbers.



Although a 255/85R16 is slightly over 33" tall.

Also I'm using LT-77 ratios, not R380 and I know there have been several 5th gear ones. I think I'm using the shortest, so chances are you'll be pulling more mph per 1000rpm.

I'm not saying it won't work, but it maybe won't be the best setup. And motorway speed you might struggle to keep it on the boil in 5th gear, unless you want to try and run in excess of 80mph all the time.


The bigger issue is off road. Although note, Series transfer boxes used different low range ratio's over the years. I've used the tallest here, so it might not be so bad if you have a 2.89:1 low range.

But certainly you'll loose your low speed craw ability.


I'd need to run the figures, but I suspect your setup puts your gearing similar or slightly worse than running 35" tall tyres on a standard Defender. Normally for those you'd want to change to 4.10:1 diffs.

All said and done. You have two main choices that I can see.

Opt for a different build and go LT-230, although you'll want to be able to make it 2wd only for road use (I think there is a kit).

Or stick with your current build, see how it goes and if needed look at changing the diffs.

I suspect cost wise there probably isn't much in it.

Thank you for the reply,i agree it does look like its going to be too far out which was my worry, i was trying to avoid using the lt230 but i am running out of options. i still have the standard salisbury but then that goes too far the other way according to ashcroft calculator it would be 2957 at 70 + i have just rebuilt the axles. this is really holding up the build at the moment sometimes i think i should of just left it alone :/