Overdrive Diagnostics

By Tom Mason

Originally published in the Austin-Healey Magazine, December 1995 and January 1996


December 1995 – Part 1


Winter’s surly grasp is coming early to Minnesota. After a summer of record heat and humidity, all of a sudden they are talking about frost and maybe rain mixed with snow for the next two days. I love it.


Having a 45-minute drive to work these days leaves me lots of time to think. I thought I was done writing any more columns. After all, in the last live years most everything that can go wrong with a Healey has been written about. And now that I have an electronic ignition and fuel pump, I was thinking my Healey was just about bulletproof.


Anyway, about half way to work this morning my Healey started to refuse to go into overdrive. Finally it engaged and worked for a while. Then on driving home tonight it was totally dead. Driving sans overdrive is a real pain on the highway—it was hard to make 55 or 60 MPH.


I checked the electrical first, and sadly, the solenoid seemed to be engaging just fine. I could hear it click as I moved the gear lever back and forth in neutral. I even got under the car to verify that the solenoid was doing its thing correctly. I pulled the overdrive drain plug hoping for a choked filter—no such luck.


Out with the shop manual. My next move was to remove the side cover and check the oil pump and oil pressure. Before I can do that I get to remove the tunnel—you know, like when you do a clutch. It’s just not my favorite job, but it gives me the chance to write another column. I thought about asking one of the other tech guys for advice on overdrive problems, but that would be too embarrassing—unless I gave them a different name.


To be continued....


January 1996 – Part 2


I had today off from work so I did the hardest part of beginning to fix my overdrive, which is just starting the project. Actually, taking off the tunnel only took about an hour or less. First the center arm rest, then the console with radio. The seat belts come off, and then the center tunnel carpet, and then ten sheet-metal screws and the fiberglass tunnel can be removed. The speedometer also has to be disconnected from the gauge end.


Well, that wasn't so bad after all. Actually, we are at the fun part of looking at the tranny and OD unit. I reread the section in the service manual about the OD last night.


The first thing to do is to remove the operating valve cover, which is a half-inch cap, more or lesson the top of the OD. Check pages G-2 & G-5 in your service manual. I also made sure the solenoid was moving up and down.


I then jacked up the car and started the car to let it run in gear. Well, the OD pump began to pump oil up the uncovered operating valve hole.


Be careful: the turning drive shaft has the power to seriously hurt you.


So at this point I knew that the oil pump was not the problem. I had hoped that was the problem because it's the easier fix.


I sat in the car and realized that I probably was going to have to take the OD off and out of the car. Probably a bad accumulator or seal, or worse. However, before I did that I did one more thing. I ran the car and took the solenoid off the left side and tried engaging the OD manually operating the rod and linkage on the passenger side of the OD. Well, guess what? It worked!


I cleaned up the sides of the actuating rod and oiled it, and installed a new solenoid. I then test drove the car and the overdrive worked. I guess the old solenoid just got weak or tired. Well I am happy to not have to tear into my OD just yet, they really should last over 200k unless they are abused. Maybe these checks on your overdrive will save you some grief, as they did me and my car. I vacuumed the car and waxed the leather with classic leather wax before I put it in the garage. I didn't even mind the rain that started.


Life is good.


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