My Ford Tractors

ENGINE TO TRANSMISSION ADAPTER

The design of my Ford Flathead V8 to 8N Tractor A-dapter is done. I believe most of the kits used a one-piece casting to mate the Tractor transmission to the V8. Sand casting is similar to the plastic molding used to create the new plastic dust cover for my distributor. Make a mold, pour the molten metal, then knock the finished part out of the mold. Sand casting my adapter was considered for a very brief moment. For some reason attempting to pour large quantities of molten lava into a mold does not seem like something my homeowner's insurance should be tested with.
The adapter needs to be approx. 1-1/2" thick. This is due to where the flywheel on the V8 sits in relation to the back edge of the engine block. The 4-cylinder engine covers most of the flywheel and clutch assembly. This V8 engine used a separate bellhousing casting that fits between the engine and transmission. My adapter will be two plates (engine and transmission). The two plates will be welded to a steel ring.
Parts to make the two plates were ordered from emachineshop.com.
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This is the same place that makes the parts for my hydraulic pump brackets.

The photo above is a 48" piece of 1/4" x 3/4" flat bar being bent on my tubing bender. This will be one of the "filler rings" between my V8 engine plate and 8N transmission plate. The tubing bender does a great job up to about 8" from each end. The ends were bent on my shop press to complete the circle.

These cut parts were delivered Tuesday. Three 120 degree plates make the 360 degree engine flange for my custom V8 to 8N Adapter. The other three pieces for the 8N transmission plate should show up tomorrow. The machine shop could have cut each of these plates as a single complete circle. That was the obvious first choice, but the cost would have been much higher for cutting and shipping those very large pieces. Making each flange in three pieces makes the assembly process much more difficult. The seams in each plate were offset, so the welded seams don't line up. It was a bit of a puzzle to figure out how the 3 pieces fit together.

The pieces of each plate were bolted to the engine, and tack-welded together. Then the transmission plate was checked for fit on the transmission.

These are the drawings I created from scratch to make the 1949 Ford Flathead to 8N Tractor Transmission adapter plates.

If you need CAD drawing of these parts, send a request using the contact form near the bottom of my CONTACT, or PARTS page. I will be happy to send the drawing as a 2010 DXF file that can be imported to most CAD software. Please keep in mind these are measured drawings. They were not based on actual factory drawings of these parts, so I cannot swear these drawings will be accurate enough for your purposes.

My adapter does not allow use of the original starter drive that extends past the flywheel. Making clearance for the starter drive would have required hacking a big hole in the right side of the transmission case. Sorry Ford, but that starter design just stinks. It's darn near impossible to install the drive around the flywheel, and that extra long shaft makes the starter drive much weaker than it should be. I am going to use an aftermarket, high torque, gear-reduction starter. These smaller starters have the small drive gear close to the starter motor, and engage from the front (engine side) of the flywheel.

The photo above is the second piece of steel bar bent in a circle to fit around the inside diameter of the adapter. My tubing bender is still new to me, so making perfect circles like this is fun. Having no idea how to calculate final strength of anything as complex as this adapter, my usual method is to make everything as strong as space permits. There is a 1/4" thick plate bolted to the engine with a 1/4" thick by 3/4" wide circle around the outside, and a 1/8" thick by 3/4" wide circle around the inside. Both of these circles are what supports the 1/2" thick transmission flange the 8N transmission will bolt to. Everything was tack-welded in place, then test-fit to each side before doing a continuous weld all the way around every seam.

The adapter in these photos is mostly done. There is still a small gap to fill where the starter will mount to the engine side of the flange. The small piece for that just hasn't been welded in place yet. The six holes in the transmission flange that line up with the engine bolts have been enlarged to for allen head bolts that will hold this adapter to the engine. There was no way standard hex head bolts would work in the space available. Grade 8 Allen Head fasteners will work, and will still be accessible with the transmission in place.

Some of those welds are pretty ugly. It will be interesting to see how well this adapter can be prepped and finished. The goal of this build was to have everything look like it might have been available as a factory option. The exposed welds on this part do not look anything like a factory part. Grinding those welds smooth would remove much of the strength. Body filler or fiberglass are used all the time on custom cars, but I do not feel they are appropriate or durable enough for a tractor. I will most likely just make one more pass over the welds for appearance.

TRANSMISSION AND HOWARD AUXILIARY

Transmission–The best news with the 1951 tractor so far is the transmission appears to have been recently rebuilt. The bearings are not nearly as loose as I expected, and the main input gear shows almost no wear.
One of the complaints about 8N tractors with V8 engines is that they are not very practical to use. It's the same old complaint that the N-tractors are geared too fast for many modern implements.

Here's one solution to the first gear too fast problem. It's a two-speed underdrive auxiliary transmission. This Howard Creeper transmission was specifically designed to reduce the tractor ground speed without affecting PTO shaft speed. This step-down transmission was necessary for the Howard Rotavator tiller attachment to work with any of the N-Tractors. Low range is a big step-down (approx. 3.5:1). Even with a 3.5:1 step-down soil conditions on our property are no good for a tiller. I tried one once and quickly decided rocks, roots, hardpan and clay are not proper soil conditions for a tiller. At least the lesson wasn't expensive. The tiller was a gift.

Howard Creeper transmissions are very hard to find and, if any parts are required, they would likely have to be made from scratch. When this one appeared I couldn't resist buying it, even though it was several years after the tiller had been re-gifted and I had no desire to ever try using a tiller again. That was the least fun I've ever had with a tractor. For this project, the creeper transmission will allow the V8 to make some noise, without going too fast. One concern is that with decent traction the Howard low-range gear could easily provide enough torque to snap an axle. Another worry is the straight-cut gears may be noisy. The only way to find out is to try it and see what happens.

If you ever work on a transmission, don't do it on the floor like I did. Even if you have to make a bench, get the thing up close to normal working height. Your back and legs will feel much better the next day.

This pilot bearing puller proved to be a good way to pull the old transmission shaft seal out.

Front transmission bearings and races are like new, so I drove the new seal in, replaced the gasket and gave everything a light coat of grease before bolting the input shaft back on the transmission, and reinstalling the throwout bearing.

A SUCCESSFUL TEST FIT

This is the first full test of the adapter plate. The V8 flywheel is larger than the hole on the transmission side of the adapter, so the flywheel was bolted to the engine first. Then the adapter was bolted to the engine block with six socket head cap screws inserted and tightened through holes in the transmission side of the adapter. The clutch disc and pressure plate were then bolted to the flywheel.

I did not have a pilot tool to center the clutch disc while bolting the pressure plate in place, but I did have a spare 8N transmission input shaft. If a spare shaft isn't available, remove four bolts and use the one on the transmission. The clutch disc must be centered on the pilot bearing.

The back side of the adapter plate has tapped holes that match the flange on the transmission with one exception. One original mounting bolt on the right side happens to line up with the V8 starter. The adapter plate provides a replacement offset hole. A matching hole was drilled through the transmission flange to align with the new location for this bolt. This was the only change to the tractor transmission. No changes were made to the engine block.

These are close-ups of the adapter. The access holes for the engine bolts are visible. I'm not worried the bolts will come loose, but it's a bonus that this adapter allows the engine mounting bolts to be re-tightened without removing the transmission.

When bringing the engine and transmission together it helps to have them perfectly aligned. Some smart people have built tractor splitting jigs. A frame on casters that has separate mounts for each piece of the tractor, and the ability to individually slide the pieces in a straight line. One of these days maybe I will build or buy one of those. For now I use some simple guide pins made from 3" bolts with the heads cut off, and ground to a dull point. With two or three these guide pins threaded into the engine flange, it's much easier to get everything lined up. It's nearly impossible to perfectly align the transmission splines with the clutch disc splines, but once the two are touching, the engine or transmission can be turned slightly, and the splines will slip together. This one was really that easy, and no matter how carefully the adapter was made, it was still a relief when all the bolts lined up.

The second photo of the right side shows the small bump for the starter drive gear. This adapter plate was designed to use the aftermarket gear reduction type starter that engages from the front. The original type starter drive was similar to the standard 8N tractor starter. The drive extended past the flywheel. Making room for the original type drive would have meant hacking a great big hole in the transmission housing. The shorter shaft on the aftermarket starter is much stronger than the original design, and is much easier to install. I saw no point in doing extra work to use the inferior original type drive.

Now the bad news, the V8 clutch assembly is too big to work properly in the 8N transmission. I knew that, but in my haste to put this together I bolted the V8 pressure plate on with the 8N clutch disc. The larger diameter V8 flywheel must be used for the starter to work. My plan was to drill and tap a new set of holes in the flywheel for the smaller 8N pressure plate, duh. Forgot about that little detail. Oh well, there are no step-by-step instructions for a custom project like this. The V8 pressure plate actually almost fits. It just won't turn a full circle in there. It might be possible to do some grinding inside the transmission housing to make the V8 parts work, but I think it's going to be better to use the 8N pressure plate.

Another issue was the clutch adjustment. The adapter was carefully designed so the transmission input shaft would be the right depth to fit in the flywheel pilot bearing. That worked out great, but for some reason the pressure plate fingers ended up forward of the original location. I've checked several different pressure plates, and the fingers all move forward the same amount when installed with the new clutch disc. There isn't nearly enough adjustment in the linkage to move the release bearing forward far enough to release the clutch. My first solution was to modify the clutch release bearing hub to make up the extra length.

However, that modification will limit how much wear the linkage could adjust for. Then I started worrying about what the extra travel would do the the pressure plate springs. After further review, this problem was actually caused by the new clutch disc I bought. More crap parts from the land of "almost fits". The replacement clutch disc is thicker than the original tractor part, so the linkage does not have enough travel for it to work. Problem solved, clean-up a used clutch disc and install that with an original unmodified release hub. Problem solved!

Drilling the V8 flywheel to fit the smaller 8N clutch assembly was simple enough. Located and centered the smaller 8N clutch pressure plate using the original holes for the V8 clutch as a guide. Made some simple spacers to temporarily bolt the 8N pressure plate in place, exactly centered on the flywheel. Then marked new holes right through the holes in the pressure plate.

A hub adapter was cobbled together so the flywheel could be mounted on the center hole of my new floor-mounted drill press. This made certain the new holes are aligned properly. The pressure plate uses shoulder bolts, so the first part of the holes must be counter-bored slightly larger than the OD of the threads.

This is another photo of the adapter plate. It's been way too cold to paint, unless the parts are small enough to bring into the shop and hang by the wood stove, like this.

There were no alignment issues, other than the clutch disc being too thick, so the adapter was primed, and painted with Rust-Oleum Sunrise Red.

Digging through my collection of used clutch discs I found four completely different types.

All of these are 9" discs that came out of N-Tractors. These four appear to be in very good condition with little wear. They are not the same thickness. The top and right ones are 0.375" to 0.40" thick. The other two are only 0.30" thick. The new clutch disc used for the previous test-fit was too thick and caused a linkage problem. Using a thinner disc fixed that. Of the two thin ones here, the solid one with no springs is an original type 9N tractor disc. I've decided to use the one with springs on the left because it has more friction material surface area. Assuming the friction material on these is similar, having more material in contact with the flywheel and pressure plate should give the clutch more grip.

This was a snow day. I spent the first half of the day shoveling and plowing snow with the 8N. It was only 7 inches of powder, about half as much as the weather guessers said we might get. That was a relief. With morning temps in the teens, I plugged in a block heater before trying to start the 8N.

Engine Install Sequence and More Test Fits

This is a little better engine install sequence than I've been doing. Tractor splits and engine installs have become so easy I usually breeze through them without slowing down enough to take photos. There are a few tricks that make the job easier, especially when working solo. Before installing the flywheel, carefully scrape and clean the mating areas between the flywheel and crank. Make sure there is no debris in there that might make the flywheel wobble. Inspect and replace the pilot bushing or bearing if there is any quesstion.

How do you remove an old pilot bushing? Good question. One way would be to hook it with an attachment on a slide hammer and knock it out of there. Another way would be to drill most of the bushing material out, then collapse and remove the rest. By far the easiest way is to take a grease gun, fill the bushing and area behind it with grease, insert a pilot tool into the bushing and whack the pilot tool with a hammer. Put another gob of grease in the bushing, reinsert pilot tool, give it another whack. The grease has nowhere to go and will force the old bushing out.

The flywheel bolts on this engine had holes for safety wire. The trick to safety wire is to wire the bolts together so the wire prevents them from coming loose. As the wire is tightened, it should appear to be trying to turn each bolt tighter. The wire just needs to be snug. It will snap if tightened much more than that. Then my custom-made transmission adapter is bolted onto the engine with six allen head cap screws.

This is using a spare transmission input shaft as a pilot tool to install the clutch disc and pressure plate. This is the "tool" that was used to remove the old pilot bushing with grease as described above. Tighten the pressure plate bolts in rotation 1/2 turn at a time, so the pressure plate is pulled into place evenly. Wiggle the pilot tool to make sure the clutch disk is centered just before the pressure plate gets a death grip on it.

Next install two or three pilot bolts. These are simply long bolts with the heads cut off. The cut ends are then rounded-off on the grinder. These bolts will help align and guide the engine onto the transmission. In this case, the transmission end of the tractor is supported by jack stands.

Raise the engine off the blocks and slip the pilot bolts into the corresponding holes in the transmission. Hold gentle pressure on the engine and use a ratchet and socket on the crank bolt to turn the crankshaft to align the splines. The clutch should slip easily onto the transmission input shaft. This should go easy. There is no need to force anything. Do not use the bolts to force the engine and transmission together. Find out what is hanging things up and try again. When the engine flange gently bumps into the transmission flange, start installing a few bolts around the flange. Don't snug anything up until there is a bolt or pilot in every hole. Snug a few bolts, remove the pilot shafts, install the last bolts, and tighten them all. Go around again to make sure all the bolts are tight.

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