The engine problems I repaired were mostly from overheating. Radiator, fan belts and water pumps were the root cause. This high heat would cause the piston to start seizing in the bore. This drag would add wear to the wrist pin bearing and it would cause it to wear out early. It happens to #4 because it is the furthest from the water pump. You would get a light knock that is most pronounced when the engine is decelerating. It will change its sound when the fuel line is loosened to "cutout" the cylinder.
The head gasket failure is common on this engine too. Heat again was the cause.
The transmission transferring oil with the bevel gear case likely happen when the machine worked up hill one day and down hill on the other. It has a seal in the rear of the transmission but, a rebuild is needed to access it.
The steering lines would not work if something was crossed. The most common failure on these tractors is the valve control bearings wear out and don't release the steering clutch correctly. You will have to force a turn to get it to do anything.
Just turn the drive shaft by hand, it should turn with some effort but, not need a bar to do this. Normally it can be done by hand but, not always. After it first moves it should turn a little easier. If you must force it, then you may have a problem.
There are far too many issues to get into now about testing convertors. BotXXXXX XXXXXne is it still should start fine if the shaft turns easy and most problems are overheating the oil.
Be sure to double check the starting system, I have skipped over this simple stuff before and it always came back to bite me.
You should be able to remove the injectors and have the starter spin the engine easily.
I hope this is being helpful, let me know if I may be going in the wrong direction.