Gday all

Last year in October i purchased my second ever patrol a 2011 GU ever since i have had it i have had issues with keeping her cool whilst towing, especially around the 80-100km/h area. So i have avoided towing with it. And on Xmas eve she blew the tranny (merry xmas to me). I replaced it with a second hand transmission from a wrecker with 10,000kms on it. I still have same issue 80-100kms temp rapidly climes when towing, Last weekend however i did a trip to kakadu (no trailer) and at 100-105 km/h she started running warm again (there was a decent headwind fyi) it didnt feel like she was working to hard to stay at that speed but i decided to disengage o/d and almost immediately the temp dropped to where it always sits just under half. this happend a few times and always same result. trip home was perfect with tail wind sat between 110-120 (130kmh speedlimit) with little to no effort around 2500rpm and temp did not move once.

I have rebuilt the viscuss hub i have had radiator flushed and checked with a temp camera to ensure radiator is doing its job, and serviced frequently.

All the shops in darwin say its something different i have spent a couple grand chasing this issue and also believe its cost me one transmission already.

Mods wise i have only fitted a provent catch can, it has had since i got it a lift guessing between 2-3", 305/70R16 tyres and a 3" exhaust system, I have been told that its way faster then a normal zd30 should be but a friend checked boost through the computer and it came back at 30psi which we freaked out about but nissan told us that thats includes 15psi atmosphere pressure.

Help me guys before i go broke (to late) or the wife hangs me.

is it the transmission or something else and how the hell do i fix it.