There's quite a bit of discussion on here about slack in the transmission on Land Rovers. It seems to be something they're prone to. There are a lot of splined joints between the engine and the wheels and they're usually where it originates. In my case the biggest improvement is achieved by replacing the drive flanges, especially on the rear. But over a period of time it comes back, even with well lubricated splines. Most of the splined items like drive flanges and half shafts are not prohibitively expensive, so it's not necessarily a major problem. Where slack is more problematic is in things like CV joints or in gear wheels, but once again, they can all be taken apart and replaced. It's not terminal, it's just about being aware that work might be needed.