In early March of 2016 I had just taken a corner and the transmission (Automatic) dropped from 3rd into 1st (presumably) and over revved the motor in doing so, this caused the me to loose control of the vehicle (also no thanks to the tires being fairly well worn, I had it booked in to have them changed when I got back to Perth. The vehicle left the road and dropped 1.5 metres into some shrubs. My friends whom I was following, assumed I was making u-turn until they saw the big cloud of red dust arise from the side of the road.
A few days prior to the accident the car had been going into a sort of transmission limp mode, I was unsure of what the problem may have been and continued to use it as it was functioning ok. The Limp mode caused the transmission to stick in 3rd or 4th and stay there until the engine was shut off. If the vehicle didn't get to a speed high enough to go into 4th it would be fine and function as normal in 1st, 2nd and 3rd. 5th was inaccessible at all times, it did try to go into 5th but failed and went into limp mode. If you experience any of these symptoms stop driving the vehicle immediately, these transmissions are used in a variety of different Nissan vehicles such as some 350Zs, Pathfinders etc depending on year.
A service manual is a great help in diagnosing the cause, I narrowed it down to the solenoids on the computer (TCM) that controls the automatic, which is housed in the underside of the automatic in the oil pan. I ordered some refurbished solenoids off of ebay, I tested them when I received them with a multi meter set on OHMs, they were within the tolerances described in the service manual. I set out and pulled the oil pan off, which had no oil left in it due to a broken oil cooler pipe on the front of the vehicle, the transmission had pumped all of the oil out when I was getting it out of the ditch. I ended up finding a wire broken but still just touching on the top side of the Transmission Control Module (TCM) where the solenoids are located. I wrapped some wire around it soldered it back together, while I was there I strengthened the other wires with a layer of solder (see pictures below). I also found the main wiring harness which goes to the TCM had rubbed on the exhaust and worn through the cables. These two faults would have most likely caused the the transmission to do what it did. It hasn't done it since the repair...
The front end was totally destroyed, the glass fiber composite frame (radiator support) that supports the radiator had cracked in a few different places so that needed to be replaced. The weeks old radiator ended up with the thermo-fan going through it, which wrecked the months old fan-clutch as well. I managed to source parts mostly from Australia, but with great difficulty. Some parts had to be shipped in from the USA, as they have the same vehicle over but with different name, it is called an Infiniti G35 over there where as it's called a Nissan Skyline 350GT here in Aus. The front bumper I painted myself turned out to be for a coupe not a sedan so it was a slightly different shape around the lights, which I used the multi tool on to fix, since I had already spent hours of sanding and costly paint on. I replaced the thermo-fan with a Italian made high power fan which is controlled by a DaviesCraig thermo controller.
The Skyline is running well and no problems since the repairs.
Cooling Problems: I also had cooling problems with the vehicle a while before the crash, but and upgrade to an Aluminium radiator which is 3 times thicker than the original one fixed the problem. Before that I replaced the thermostat, thermo-fan clutch, flushed the cooling system, bled the cooling system, none of these made a slight difference until I changed the radiator.