There is a wide range of possible ratios for the LT230 transfer case, which was fitted to the Defender, Discovery, and Range Rover.

Located on the rear face of the transfer case, to the left of the handbrake drum, the prefix of the serial number should help you identify the ratio—that is, the gear ratio of your transfer case.
The higher the ratio, the shorter the gearing will be.
A lower ratio will allow your engine to run at lower RPM for the same given speed.

Here is a table showing the different ratios:

LT 230 Ratios

12D = 1.667
13D = 1.410
14D = 1.003
15D = 1.192
20D = 1.667
21D = 1.667
22D = 1.410
25D = 1.410
26D = 1.003
27D = 1.192
28D = 1.222
29D = 1.192
32D = 1.222
34A = 1.410
36D = 1.211
37D = 1.211
38D = 1.211
40D = 1.211
41D= 1.211
43D = 1.410
47D = 1.667
57D = 1.410
59D = 1.211
61D = 1.211
62D = 1.211
68D = 1.211
69D = 1.211
70D = 1.211
80D = 1.211
81D = 1.211

If you don’t have a serial number, or if you want to check the ratio yourself, here is a method to identify it.
Engage the differential lock and put the transfer case in high range. Turn the differential output flange one full turn and observe how many turns occur on the “gearbox input” side. Imagine a dial divided into four quarters.

Here is a video from Ashcroft, the specialist, explaining the procedure:

https://www.youtube.com/watch?v=19d_mCVDEho