This software is designed for you to accurately compare and calculate the gear ratios of your landrover when the gearing is changed from stock by different tyres etc.
We are interested in the combination of 5 factors which make up the gearing.
1) Gearbox
2) Transfer case
3) Overdrive or Underdrive
4) Differential ratio
5) Tyre diameter
by inputting the above data into the table below and clicking “calculate ratios”, the software will show :
a) a table of the final drive ratios, (this is how many engine revs to make the wheel turn once)
b) table of the speed (in 10mph steps) and engine revs when in high range for each gear
c) graph of the speed and engine revs when in high range for each gear
d) table of the speed (in 10mph steps) and engine revs when in low range for each gear
e) graph of the speed and engine revs when in low range for each gear
Example 1: Stock TD5 90
1) Gearbox, R 380, Variant type 68A
2) Transfer case, LT230, Variant 43D
3) Overdrive, none
4) Diff ratio, 3.54
5) Tyre diameter, (use 2 x rolling radius for accuracy) 31 Inch
Revs at 70mph = 2919 (too high, that’s why people fit the 1.222 gears, drops this to 2530)
Example 2: Stock 300 Tdi Disco
1) Gearbox, R 380, Variant type 55A
2) Transfer case, LT230, Variant 28D
3) Overdrive, none
4) Diff ratio, 3.54
5) Tyre diameter, 31 Inch
revs at 70mph =2530,
now fit some 35 Inch Tyres!
revs at 70mph = 2240, bit too low, it will struggle to pull 5th, so lets fit some 4.12 gears in the diffs to lower the high and low range,
revs at 70mph = 2607, that’s close enough to the original 2530 and it will drive much better.
There are of course other factors to take into account such as the type of engine, ie torquey 2.8 TGV or a cammy high revs V8, also aerodynamics (or lack of it) needs to be taken into account.
The ideal target RPM is 2,700 revs at 70 mph in top gear. If you use the ratio calculator to get as near to this as possible.
Please email us if you have any queries in using this calculator. I hope you will find this a very useful tool.