Troopy Gearbox/Transfercase problems

Hi
Maybe a fairley overdrive was on it before. Is there a hole in the floor where the third stick went through? There has to be a problem with the lubrication or heat, as any misalignment would end up with teeth worn strange and wheeeeeering noises all the time. Have you been checking the oil level on the transfer at all? sometimes the early boxes pushed the oil out of the transfer into the gearbox, and run dry. The easy fix to this was a hose between fillers.
Andrewwheredayathinkwer mike?

thinking along the same thoughts as andrew, had a mate with similar problem in his 96 trayback. The cause being oil from the transfer ending up in the gearbox due to leaky seal hence excessive heat in the transfer causing the wear. Quick solution is what they call the "balancing pipe" between the two filler plugs, he had no troubles after that.

As a past owner of three 5 speed Landcruisers one a brand new HJ75 and a retired diesel mechanic,20 yrs on 4x4 vehicles I can relate to your problem.
The gearboxes have a history of the problems already mentioned oil transfer etc due to hardening of the seal between the transfer and gearbox due to prolonged heat however your gearbox should not have failed after only 12 000K if properly rebuilt and run with the correct oil. The aftermarket parts and bearings that can be bought and were probably fitted to your unit as they are quite a bit cheaper than genuine Toyota are usually quite OK. Gears and bearings dont usually lose their hardness unless they have been overheated or were not hardened properly to start with. If parts from another unit were fitted and were in good condition they also should not cause a problem.Has either box run out of oil or has it been run with the correct oil? or have you done a lot of towing in 5th gear? If you can rule out those questions I would be looking for the bloke who did the rebuild.
In 1983 Toyota brought out the first 5 speed gearbox and they have had three main problems, the oil transfer, dosent usually happen until the seal hardens .
Bearing failure if driven for long distance in 5th with a heavy load or towing a load, and stripping the splines off the main shaft by the constant mesh gear if the nut on the shaft has not been tightened regularly. As you and I know rebuilds are expensive I had three fail on me,,Good luck.

As the other replys, it does sound like an extraordinary occurrance, that has to be related to the lack of lubricant. Carefull monitoring of the oil levels in both the boxes will have to be done to make sure oil is not transferring. I would suggest a top brand oil like Penrite and the addition of an oil stabiliser like Morey's. These two combined will help to lower heat build up as well. It may pay you to install a gearbox temperature gauge to keep an eye on the transfer, that way you can be alerted to any impending failure. Also, take regular oil samples on a mirror slide to check for minute metal particles in the oil. This too will alert you to a possible early warning. My guess is somebody, sometime has missed replacing an ageing part that is further detereiorating and sending metal through the oil and thus buggering every other part as well. Hope this helps you.