Part 1 detailed the disassembly of the main transmission. From there, I continued to start to disassemble the overdrive unit. It's a Laycock D-type overdrive that was used in various cars, and I wanted to understand how it works! Of course, since the trans and overdrive share the same oil supply, it was a rusty mess too:
The rusty bit in the center is called the "planet housing," and the gears inside are the planets. That whole mechanism spins in a part called the "annulus" and it looked pretty rough when I first removed it. I managed to chuck it in the lathe, and spin it very slowly while I cleaned it up with wet-or-dry paper used with oil.
It got rid of the rust, but close examination showed a series of rust pits in the face, exactly matching the rivets in the friction lining that sat on that face for who knows how long. I sent this photo to my gurus, and they agreed that it should still work. Good news, because that part is no longer available as a replacement part.
I won't bore you with all the pictures of rust, but this one has more info. This is the front (that is, toward the front of the car) of the part called the "cone clutch" - it's tapered on the other side to match the tapered face on the annulus above. As you can see, there's a bearing inside, one of three in the overdrive unit, and all three were packed with rusty sludge. An easy decision to replace all three.
But here's an interesting data point: I was ordering the overdrive parts from Moss Motors, which serves the British car community. As I said, that Laycock overdrive is used in lots of different cars, and I went with Moss because they had the most parts still available. BUT.... the bearing on the output side is unique to the vehicle, or make, or something, so the one I ordered didn't fit! I was able to get a number off the old one, and Jake R. helped me find a replacement.
More gunk - this is the cover of the filter housing, with the filter still inside.
The filter is a brass-colored mesh over a frame of a coarser mesh, and I was amazed to see that it had blown out. I guess it was so packed with gunk that the high pressure from the pump finally overwhelmed it.
That led to a several-week search for a new one. I found exactly one in the whole world, on British eBay. Sadly, that one was marked, "Will not ship to USA." I contacted the seller and asked if he would consider shipping, which led to a series of miscommunications, including my buying the part twice, and the seller having to cancel the transaction because the shipping option wouldn't work. Finally, he quit answering my emails. So, I did a really bad patch, soldering the hole shut. It decreases the surface area of the filter, but at least large particles can't get through anymore.
Here's my theory of why this overdrive trans fell into disrepair and final abandonment: the center bolt is actually a cover for the pump assembly. You can see that someone tried to remove it, rounded the nut, and then unsuccessfully tried to remove it with a chisel:
I asked Jake R. for his advice, and he said, "Get the biggest nut you can find, put it over the plug, and weld the heck out of it with your MIG welder. Really fire it up!" I was reticent, but he assured me that I would not damage the housing. SO..... I found a really big nut (it takes a 1-1/8" wrench) and zapped it mightily:
It still took a mighty pull on that long 1-1/8" wrench, but it yielded, and has been fine since. I can't find a replacement for that particular plug and don't feel like making one from scratch, so that monster nut is now part of that overdrive unit's story!
After getting the entire overdrive apart and ordering all the new parts I could source, I turned my attention back to the transmission. I had ordered parts for that too, and Joe Lazenby kindly gifted me some extra gears and parts to replace some of the rusty ones. I put it all back together, and was dismayed to find that there was a spot in the rotation that bound tight. My mind immediately went to the worst case: what if the impact that broke the shifter actually slightly bent the irreplaceable main shaft? It's much longer than the M40 transmission's main shaft, and is no longer available as a new replacement part. I pulled everything apart, and put it in the lathe (turning by hand) to check for straightness:
Thankfully, it was perfectly straight. I started a pretty long process of trying different things to find the source of the bind. Finally, today Troy Nace came by to help me with a few things, and he saw something my eyes couldn't register. He looked at one of the brand new thrust washers for the gear cluster called the "layshaft" and said, "This is bent." Sure enough, I put it on a flat surface and it rocked. Replacing it with one of the used ones immediately cured the problem. I didn't even take a picture of that washer, but if you imaging a funny looking brass washer, you're close.
After that, it all went back together quickly, and we were able to put the transmission (still missing the overdrive) on my test jig I created when we built the M40 transmission currently in Beck TD. It works great, shifts easily, and seem to be quiet. Result!
I undertook this process to better understand how an overdrive works, and I'm partway there. I actually can look at the parts of the Laycock unit, and know what each one is, and how it goes together. However, I still have the most vague notion of how the planetary gearset works. I'll keep working on that.
Next up: reassemble the overdrive unit with all the new parts I could find, and hope that it works!
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