Thread: KZJ78 Transmission problems

A month or 2 back my 94 Landcruiser, KZJ78 started dropping down a gear as I was cruising on the seal, usually on an ever so gentle down slope. It wasnt overdrive, it was the normal gears. Might not happen for 50km's, might happen in 5km's. Very sporadic, and sometimes I might get 100 km's or more then it would do it several times. I turn the overdrive off for a minute or 2 travelling at about 3000rpm/100kph, then switch it back in to overdrive and it seems to go away until next time, or it could do this every 5 minutes for ages. Bloody frustrating.
Has been to mechanic 3 times, first time had the oil all drained, flushed, filters cleaned and new oil put in. Worked for about 100km. Second time the mechanic fitted a large as accessory oil cooler cos he said the original oil had been heated. I had towed a trailer a couple of times where the AT Temp light came on, so knocked it down a gear or 2 until it cooled down. Third time was last week and he replaced 3 wires in the loom that may have been shorting, possibly the sensor sender wires, who knows.
Went for a big arsed drive today and bugger me it still does it. totally random, no rhyme or reason when it will do it. Drove 50km, dropped down, did the old Overdrive off for a minute or 2 and it fixed it. Drove over another 100km and then it started at ti again.
Any one have any idea of where I start looking to find the fault?