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Mercury 3 Speed with R10 Overdrive Rebuild Part 1

Updated: Dec 27, 2019

(A few years ago I submitted the following article to the Y Block Magazine and it was published. I have decided to post it here for those that have had questions about the transmission that is in the 1955 Ford Fairlane Club Sedan.)

Mercury 3 Speed with R10 Overdrive Rebuild

Not too long ago I began to toy around with the idea of putting a manual transmission in the 1955 Ford Fairlane Club Sedan. The 292 in the car really goes, but I knew the Fordomatic was a real power robber. A very generous man from the Midwest called me up one day to make an offer I could not refuse. He had contacted me through a website that brought Ford enthusiasts together, and after learning I was a “Y Block guy” he wanted to help out. I was told that in the 70’s he had been given what he said was a T-86? three speed with R10 overdrive transmission and it had done nothing but lie around the shop for a few decades. If I wanted it, he would simply ship it out to me for whatever the cost was to him. Of course I said I would be interested and on his word I would pay the shipping and have him box it up and sent it out here to the shop.

A few weeks passed by and lo and behold but what should greet me at my front door when I got home in the evening? A mutilated box on my doorstep, complete with an oil puddle and shards of cardboard. When I cleaned things up and opened up the box I could tell the previous owner had packed it well with foam, extra support, and had wired all small/loose parts to the transmission case so as not to lose anything. (I am glad he did that – there were holes all around that box!) The original solenoid, governor, shift levers, and cable were all included.

The transmission arrived with a mutilated box and a broken ear on the main case.

To my dismay, one of the ears on the main case had broken off during transit with the boys in brown, and because of all of the holes in the box, the rest of the mounting ear was nowhere to be found. I thought about what to do… Mount it with only 3 bolts? Part out this transmission and find another? Fight with UPS and wait several months for no resolution? (already been down that road with parts I have shipped to others before) Since I only paid the shipping, and I thought I had a good transmission I decided to wait until I could find another main case and just swap out all of the gears and do a restoration of the entire transmission itself. So, I removed the cover plate and looked inside – the gears looked to be in very good shape, no broken teeth, good syncros, and the overall appearance of the interior seemed to indicate that the previous owner had kept the oil level up.

Now mind you, what I know about transmissions you could put in a thimble, and if you turned that knowledge into gasoline it might be enough to fuel a gnat’s scooter when he takes a trip around a Cheerio. But I always enjoy a challenge, and besides, in the 50’s this overdrive was quite the ticket for people who drove those cars and trucks over the highway at speed. I was told this was a T86, and not knowing any better I went that route using that nomenclature when talking to people, doing research, etc. (more on that later) Anyhow, it was not too long before my memory came to life and reminded me that Dennis Leeking up in Pennsylvania was running an R10 overdrive in his 3 speed 1954 F100 with a hot rod Y block. Maybe he would have some leads on a case for this transmission. At about the same time I decided to contact him was the week of a Craigslist find of a very nice Edelbrock 573 triple deuce manifold. Dennis wanted the manifold, and I wanted his empty transmission case. We swapped the parts and a little cash and away we went. Dennis was right on the money – this was the exact same case as what I had for my R10.

The main case acquired from a parts swap was in excellent shape and no broken ears!

After getting the main case back to the shop I compared the two and knew that we were in business and ready to go. Before I disassembled anything I consulted every shop manual, exploded parts diagram, Borg Warner book, various websites about overdrives in Ford cars, etc. Try as I might however, I could not find anything that matched exactly what I had. I did find a few that came close, but most of those showed a different tail shaft housing than my R10. After reading as much as I could I cleared the 9 foot wide workbench and prepped for surgery. Let me just say here to all of the uninformed such as myself – READ, READ, READ, and CONSULT, CONSULT, CONSULT. Arm yourself with as much knowledge as possible and follow the steps that Ford laid out in their manuals. My wife laughs at me because I keep a 55 Ford Shop Manual in the bathroom next to the toilet – makes for great reading while “on the throne”!

A good shop manual is worth its weight in gold when it comes to repair work!

During this whole process I kept looking for websites or other information that included tips and/or tricks on dismantling, inspecting, and reassembling the 50’s Ford manual transmissions but found very little. Why? I am not sure. Maybe it is because most people sub out this work to the professionals, or maybe because to most folks this is pretty simple. Suffice to say, I felt overwhelmed because I had no experience with work such as this but knew that if I could rebuild a Y block, then something like a manual transmission ought to be a walk in the park. For the Y block community, all of us are knowledgeable on the Y blocks – so much so that we can quote the firing order, know the compression ratios of different heads, have the block ID numbers memorized, know all the nuances of disassembly/reassembly, etc. But the knowledge of transmissions seems to be a different animal altogether. It took me a while to get some feedback on the R10 tail shaft on this transmission belonging most probably to a Mercury, and not a Ford, passenger car. One fellow who sales Ford transmission parts for a living told me that I had a 1954 transmission. There is still some debate to that and I have not clearly settled anything one way or another. I do know that this will bolt right up to a Y block and it fits the original 55/56 transmission cross member. Most of the reason I decided to do a write up on all of this is to give some tips and advice about the transmission that I found NO MANUAL covered - more about that later.

The smooth end on the tail shaft housing indicates that the transmission is a Mercury.

With the workbench clear, the dismantling began. A word of advice – use sealed containers for small parts. I made the mistake of putting all of the needle bearings on the lid of a tin can container. Wouldn’t you know it that when I had to tap on the tailshaft a few times to release it from the housing, the lid FELL OFF THE WORKBENCH and onto the floor… sigh… where did those little boogers go? I eventually found them and counted them to be sure I had them all – 22 a side (44 total) on the countershaft alone, 15 inside the snout, and 12 at the overdrive roller. Needless to say, I quickly grabbed a few clear plastic containers with sealable lids and stored the bearings properly.

Keep your bearings and small parts safe and counted by using plastic containers.

As parts were removed they were placed into either an ultrasonic cleaner or a solvent tank. I cannot say enough here about organization and a good system of parts identification and inspection. The rusty hardware on the outside of the transmission was also blasted and either painted or kept in a bag with a little bit of oil to preserve. I recommend that you DO NOT BLAST your case, tail shaft housing, adapter, or cover. Some guys do it I guess, but I would be too concerned about leftover grit grinding my gears!

I am sure that some of you reading this article would want to comment to say “take photos!” while you go through the process. That is a good idea as well, but for me I was always elbow deep into the grime, muck, and mire that I really didn’t want to clean up, take photos, get dirty, clean up, take photos, etc. Maybe there is a better way to do that, but I didn’t take too many photos of the disassembly.

I was very pleased to find parts in good repair throughout the entire disassembly. The teeth on the gears, and even the overdrive parts, looked to be in very good shape. The main bearings on each shaft cleaned up easily and had no “slop” to them. They looked almost new. But then I removed the countershaft gear assembly. The 3/4” shaft that the gear assembly rode on for all those miles showed horrible signs of wear on one side of the shaft where the needle bearings were rotating – and only on the top of the shaft, but enough to move me to find another.

The main case needed a new shaft for the countershaft gear assembly.

I put out a request for another shaft but found literally no one on the forums who had one to spare. There was a business called USA Parts Supply about an hour away from me. Maybe I should try there. They had quite a few transmission parts (like bearings, seals, solenoids) listed in their catalog for 50’s Ford transmissions. I should have called before I made the trip. The experience was horrible. I actually brought my old shaft with me to show what I needed, but when I arrived to their “showroom” not one of the 3 workers behind desks got up to help. Ok, so they’re busy – no big deal. I walked over to one of the guys and said what I needed. I could tell right away he did not speak “Ford” but the other guy at least offered to look at the shaft and try to identify it. After telling me that no one was going to have that, I was going to have to get a machine shop to make one, etc, I kind of took it back and just thought ok, maybe these guys are just the uninformed who work here. So I asked for a printed catalog and the response I got was, “We’re getting away from Ford parts, there’s no reason for me to give you a catalog.” I turned around and walked out. They still have a large Ford section on their website – don’t trust it my friends.

After this debacle, a helpful friend turned me towards VanPelt’s out in Ohio. I called them on the phone to explain the predicament via voicemail. Do you know I got a call back almost 30 minutes later? During the conversation the gentleman explained what was needed, clarified an issue that I thought I had concerning missing a washer for the countershaft (I surmised that this was the reason the one side was worn so badly – the washer was not on the shaft in the case!), and had a very helpful demeanor. Yep – VanPelt’s got my money, and the next time I need transmission parts I know exactly where to go. The fitment of the shaft, new washers, and new needle bearings was spot on. With all parts cleaned, inspected, and the new parts, seals, and gaskets acquired, we were ready for reassembly. I decided to lay out all of the parts in sequence of order, from the front to the rear, on the workbench… for the novice it was scary indeed.

The parts were all laid out in order for organization and identification purposes.

You may notice from the photo above that there is a wooden dowel sitting below the ¾” countershaft and gear set. I credit Dennis Leeking with handy idea to use the dowel as a dummy shaft so that the needle bearing and washers can sit correctly before the shaft is driven through the case and gearset putting it all into position. Being overly confident can be a humbling experience as I jumped the gun and started put things into the main case because I got to rushing things. Let it be known and stated time and again, machined parts with such intricate subassemblies as these must follow a procedure for realignment and reassembly – otherwise you risk having to take it all out again to fit the other parts correctly. I am now an expert at using dummy shafts and messing around with the main case. I could probably do it blindfolded by now. But enough about all of that, on with the rest of it!

The dowel was trimmed flush and held the bearings and small washers in place.

Wheel bearing grease and a fresh bottle of 80W90 was kept handy during the entire process so as to keep everything lubed well. The trickiest part of the main case reassembly was that the countershaft gearset had to be placed loose inside of the case while the main shaft and snout were attached. After that the countershaft was put into position. The difficulty was that I had to morph into this octopus-like alien to get all 3 large washers (one up front with a tang, and two in the rear) to go into place so I could drive the ¾” shaft all the way through. The small washers on either end of the dummy shaft stayed in place with no issues of course. One of the nuances of the R10 overdrive is that the input shaft has to be assembled to the adapter plate (the cast narrow casing between the tailshaft and the main case) to begin the installation of the gears into the main case itself.

Be careful about the installation of the synchronizer hub on the input shaft. No manual shows any information about this (that I could find) but it is possible to install the hub backwards. Everything will fit right up as it should until you get the input shaft in the case and try to install the snout that holds your 15 bearings. IT WON’T FIT if you get the hub on backwards… don’t ask me how I found out! Needless to say I wish this was covered somewhere but again, I couldn’t find any information about this. The photo above and to the left shows the input shaft with the syncro hub installed BACKWARDS – this is NOT the way you want it. If you examine the hub you can see that there is a side that will have a narrow diameter around the shaft itself – choose the smaller side of course.

A word about the main case and the two ¾” shafts (one for the reverse idler gear and the other for the clustergear set) – the photo below shows the two shafts installed while the pin is ready to be driven through the main case and through the shafts to hold them tight. You will need to align these AFTER you have installed the adapter plate and input shaft into the main case. As you can imagine, this makes lining up the small holes for the lock pin somewhat difficult. I suggest that you do what I did and test the fitment first to see the relationship. Remove the lock pin and countershaft (you will need to do that anyway to attach your snout) leaving the reverse idler shaft in position. This way when you come back to the countershaft you will only have to align its lock pin hole to get the whole works right. This can be tricky because the overdrive adapter may be in your way. You can spin the adapter though to gain access to drive the countershaft through the case. Remember that the lock pin is driven at a slight angle in relationship to the case… it is not a verifiable 90 degrees. There is an offset. When you put the countershaft in the case (before attaching the input shaft or snout) do not forget to reinstall the large washers on either end. The washer at the front has a tang that keeps it in position. The two washers at the rear are very different. The one has an oblong hole to make it spin with the gear set as it rotates, but the other is very thin and completely flat. The flat one goes against the case.

Make sure your two shafts line up BEFORE you drive the lock pin into the case.

The main case ready to receive forks and cover plate after verification of alignment.

In Part 2, we will cover the details of the R10 Borg Warner Overdrive and its rebuild/installation to the rear of the main case.

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