I posted in the X300 forum a couple days ago about rebuilding the LNA3380AD harness on my XJ12 after getting the dreaded Solenoid A and B simultaneous failure. A used one popped up, so I figured it would be easier to pop it in there and hope it was good, and worst case, have a backup for when the rebuild becomes necessary, eventually. Here are some notes from the experience for future searchers to help their project along:

- Bite the bullet and drop the exhaust. If you follow the service manual, you just need to loosen the middle section and let it droop. There's a bit of sheet metal that holds to pipes together close to the intermediate muffler which makes a convenient place to tap with a rubber mallet to slide it back. Mine was pretty dented up already, so someone else had that idea before. I was very fortunate in that my car was a southern and northwestern car, and there was incredibly small amounts of rust. Plus if you turn the car on before you seal it back up, you get to hear its impression of a Ferrari.

- Pull the transmission speed sensors while the harness is still connected to them instead of trying to disconnect in situ. Old heat cycled plastic clips break so easily, and it's easier to reconnect the harness off the car during reinstall. It's an 8mm bolt that secures the sensors to the trans case. A set of Mountain wrenches with the socket collar that stands proud of the steel makes quick work of getting into this tight spot.

- The harness is clipped to the protective cages for the speed sensors and mine was also clipped to the top of the transmission in a completely invisible and inaccessible place. I did not re-clip the harness to the top of the transmission.

- If you break a speed sensor while removing (DON'T use the plug plastic as a lever point), Delco 24203876 works just fine as a replacement at $40 instead of the $300 for JLM10958. I had to dremel off a piece of the bracket which otherwise would have blocked access to the mounting bolt from below

- Remove the transmission mount. I was able to eventually remove the 12-pin connector from the transmission without having removed the mount, but quickly realized there's no way to put the new one in with that little access. Removing the mount also made fishing the new harness relatively quick. If you jacked up the transmission by the pan to remove the mount, lower it a bit to gain clearance for fishing the harness through.

- If anybody is familiar with the Deutsch "milspec" connector catalog and wants to try to find a modern replacement, the old plug is labeled 41 95 CDG BSA 56 16-12 SN 16 F 01. The diameter of the plug with the connectors is 21.5mm.

Overall I'm pretty upset that an otherwise bulletproof transmission is compromised by a foot of thin wiring, but a long weekend of wrenching seems to have fixed the problem for now.

 

G'day Jeremy,

Well done with all that hard work. I went through a similar process with my car a lot of years ago and eventually the problem wouldn't go away so I took the car to a transmission specialist who when I told him the symptoms said "Ah it's your AFL valve"

WTF is an AFL valve I asked and he explained it all, he also said that if I had taken the car to him when the problem first appeared he could probably have done a valve body replacement but as the problem had been evident for many years he said that the only long term solution was a transmission rebuild which I had him do and no problems ever since.

Previously I had done the harness replacement and the shift solenoids with no real luck.

Attached is an explanation of AFL valves etc which you may find interesting.

Cheers,
Jeff.