Landcruiser Amazon Gearbox Problems

[John in the Desert]

I live in the United Arab Emirates and own a 100 series Landcruiser (Amazon in the UK). It is a V8 VXR with manual gearbox.

I have owned the car for 5 years and use it predominately off road in the desert.

I am experiencing gearbox problems.

The car ran fine for the first two years, then the local agent changed the clutch thrust bearing (under warranty). Since that time the gearbox has a tendency to seize up when it gets very hot. By this I mean that I am unable to change gear easily. It would appear that the clutch is not engaging or disengaging.

The problem only occurs when the outside temperature creeps over 44c. Below that the gearbox frees up and gear changes can be made.

Only 1000km ago I had to have the gearbox completely overhauled and still this problem occurs. This has been the third overhaul since the problem first occured!

The same problem occurs to two of my friends, with identical cars. Their clutches were replaced by the agent after a similar mileage and they too have the same gearbox issues off road.

The local agent therefore is totally incapable of resolving this issue.

Other people have advised me to upgrade the fluids to a higher specification (dot4 or dot5). Would this work?

Does anyone have any suggestions on how we can resolve this problem.

Would a gearbox oil cooler do the job? Is this feasible.

An interesting point to note is that the GXR Landcruiser (4.5l straight six) does not experience these problems. It is only the VXR 4.7l car, so this must run a lot hotter.

Thanks