Well, I've had a slight water leak for about 6 months now and the only clue to where it was coming from was a continuous damp patch, later a drip, at the bottom of the torque converter housing. After a thorough search for the source I was left with the possibility that it was coming from within the housing which could only mean a freeze plug (core plug in the UK and welsh plug in Oz). There is a great article on replacing the core plugs on the go.jeep website http://www.go.jeep-xj.info/HowtoWelshPlugs1.htm
and I read the factory service manual procedure for removing the AW4 transmission. This was good preparation for tackling the job but I still kept putting it off until finally, an upcoming off-road event combined with a family holiday meant it would have to be done as failure would ruin the event and the holiday.
I ordered the plugs from Jeep as I couldn't afford not to have the job finished in one weekend so wanted to be sure the right parts were to hand.
Even when I started the job I was still not 100% convinced that the leak would be within the converter housing and that after all the hassle of stripping out the transmission I would find I had missed something that was leaking from higher up above the housing. As it turned out I needn't have worried -
I had originally planned to replace the plug in the housing and the one at the back of the head but in the end I found access to the rear of the head was hampered to the point that I couldn't guarantee sucessfully tackling that plug so I decided to leave the apparantly healthy plug in place. If it fails in the future I will remove the head and replace the plugs along the side of the block at the same time. Go.Jeep did mention something about casting sand that may have caused that plug to corrode and I think I agree with him although I didn't understand what he meant until I had the plug out. when I put my finger into the water jacket void below the plug hole I found a muddy, gritty sediment that also contained some larger particles like small stones. There are 2 possibilities, perhaps the sand swirls around in the water flow abrading against the plug and causing corrosion and wear or maybe the sand sets up a chemical attack on the thin steel plug that results in the failure. I'm not sure but there has to be a reason why that plug fails first?
Now I have lost my auto box virginity I am a lot happier. The box is back in place and partially bolted on so tomorrow I just need to finish the refit and fill the auto fluid back up then see if it all still works
I will post again tomorrow to bragg about my success or ask for advice on where it all went wrong......
EDIT: for anyone who is doing this and wants to order core plugs from Jeep, the part number is - J3105394