Gear box noise 75 series

Hi, GoldMember ................. [GoldMember ???????????????]

Don't drive it anymore !!!!
My brother had a similar 'indicator' in his '96 Model 80 Series, ignored it and drove from Aelaide to Sydney .. had it checked there by a Toyota dealer.

Discovered that the gearbox/transfer case oil [not sure which] had all but disappeared, thus no lubrication and much meshing/wearing of the gears. Presumably and probably over a relatively long period of time ...... like about
8 - 10 months.

Neccessitated a complete gearbox renewal, a 3 -4 weeks delay to get a NEW box from Japan [not kept in stock in Australia any more and the Official Toyota dealers wont install either second-hand or non-genuine parts] for a total repair cost of around A$5,500 ............. ouch !!

So frightened me ['92 Model 75 Series Troopy] that I had mine checked out and then bought [on eBay $45] a Gearbox Oil Transfer Hose, which compensates for any loss of oil from one case to another [because of the seal failure between the two cases] by allowing the oil to drain back to the lower case.
Hopefully ....... said process may prevent ' your grinding noise' from causing a major drain from your wallet !!

Your 'symptoms' are almost identical to his ...................

BTW , his costs were so high because his motor was at an Official dealership [ in another state and in bits on their workbench, of course!] ........ your costs could be much less if you replaced the damaged items only ........... and got several REPUTABLE quotes as well ................

Best of luck .......... and HNY !!!!

You don't say what age the 75 is but if it is earlier than the late 90's it could be a sign of the gearbox mainshaft/transfer input gear wear which eventually leads to total loss of drive.
You can check it yourself by first parking the truck on a level spot, chocking the wheels, handbrake off and out of gear.
Then remove the PTO cover on the transfer case (after first draining the oil), then remove the black tin 'hat' up on the back top of the transfer case. This exposes the end of the mainshaft which you hold with one hand while trying to rotate the gear closest to the front of the transfer (and rear of the gearbox) with the other hand.
If you have any movement between the two it is time for repairs, gen tojo bits and labour big bucks, Don Kyatt bits and your friendly mechanic much cheaper.
My troopy had flogged the shaft and gear out by 110k to the stage where the 4mm x 2mm splines were done to a 1mm triangle, this was in a truck which was only used for private travelling, no commuting or heavy work and was serviced regularly by me.