GQ not completely bulletproof. I ahve a 97 GQ Coil Cab with a 6" lift and 35's. In the 4 years of ownership I have blown the motor which was always serviced religiously every 5000km including oils and all filters. Had an air locker in the arse and done the rear diff also. Both these are supposedly bulletproof. In saying this the car is a very clean and tidy unit as I don't thrash it out the bush rock hopping and jumping into mud holes etc. Now the only offroad stuff I mainly do is a dirt road.
How does one do those things? to this car?, the diff is driven by a motor that puts out 79BHP I think, almost a rubber band engine. the engine it's self is so overbuilt that unless it has been mistreated very badly it will simply just keep plugging on and on and on.
People have a habit of doing things baddly, it's one the biggest problems when purchasing one of these cars secondhand, servicing at 5 or 10k means nothing if an operator let it overheat somewhere along the line even if straight ofter driving it from the new car dealer that first time....from then on it's nothing higher than well looked after toyota diesel engine. An overheated engine is a stuffed engine even if later it seems to run ok again, sellers will never tell this secret.
People run oiled filters, egt too high, do homework on the diffs - lapping by eye/feel, if they where toyota's their mistakes would be noticed just down the road but being more of truck drive train, very often the next owner gets that bill.
It does read like you got stung.