Project Super C, Taking Off the Power Take-Off

FBN Network

Oct 10, 2019

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This is the 11th post in our ongoing series on Project Super C. We are chronicling the rehabilitation of our 1954 Farmall Super C tractor, which has taken up residence outside of the Farmers Business Network office. If you are new to this series, please start with the introduction to the project in our first post.

If you have been following this series of posts, you know that we have been systematically replacing the gaskets and seals that are responsible for keeping the oil inside the Super C’s transmission case because many of them have failed and have allowed oil to leak out. This time, we will be removing and overhauling the PTO mechanism, which is bolted onto the rear of the transmission case. You can see the exterior parts of the PTO mechanism in the picture below. Also visible are the oil leaks all around the perimeter of the housing, indicating a failed gasket.

Inner Workings of the PTO

Before we start pulling things apart, let’s look at how the PTO works. When the PTO lever (seen in the picture above) is pulled backwards to engage the PTO, a shaft inside the transmission case is moved forward to connect to the upper transmission shaft (which we saw in this earlier post). This shaft, which runs down the center of the left picture below, will thus rotate at the same speed as the engine.

The other end of the shaft is connected to a small gear (seen at right above), which drives a larger gear that the external splined PTO shaft is connected to. This arrangement of gears means that the external PTO shaft will rotate more slowly than the engine, and with more torque.

Rehabilitating the PTO

Now that we’ve seen how the PTO works, let’s get to rehabilitating it. We started by removing it from the tractor:

You can see that the PTO contained quite a bit of sludgy oil so it is a good thing we are cleaning it up. The PTO drive shaft (as seen earlier) also had a coat of surface rust that we removed. On the left side of the picture below you can see what the shaft looked like after cleaning, while on the right side of the picture you can see its original condition before we cleaned it.

We next turned our attention to replacing the oil seal that surrounds the external PTO shaft. Based on the oil residue around the seal and on the shaft, that seal was no longer sealing. See below:

Unfortunately this oil seal must be replaced from the back side, and that required entirely disassembling the PTO by removing the gears, shaft, bearings, etc. A lot of work just to replace one little seal!

With the oil seal replaced, we reassembled the PTO and we thought we were ready to reattach it to the transmission case and call it done. Then we realized that we were missing a tiny bullet-shaped poppet (part #48102D) whose role is to keep the PTO lever from moving except when a person pushes it. A spring pushes the poppet into one of two sockets (seen below) corresponding to the two positions that the lever can be in. This is a detent mechanism similar to what we saw with the gear shifter in an earlier post.   

While it is possible that we lost the poppet while disassembling the PTO, we think it is more likely that it was already gone. In any event, it isn’t an easily available part so we manufactured a new one by grinding down a metal rod:

If anybody else out there winds up needing this part, ours is 17mm long by 11mm wide and seems to do the job nicely. You can see us test fitting it to the sockets in the rightmost picture above. After the poppet was ready, we reinstalled it into the lever mechanism:

Before reattaching the PTO, we gave the inside of the transmission case a good cleaning to remove residual sludge and dirt. You can see the difference below between the left and right pictures:

Finally, we reattached the newly refurbished PTO, installing new gaskets as we did so. If you look closely, you can see the new oil seal around the splined PTO shaft.

This brings our project to a crossroads. When we started working on the Super C we set a first milestone of getting the tractor rolling. As it sits now, it would indeed roll and hold oil for that matter, but it wouldn’t stop because it has no brakes. And it wouldn’t be very comfortable, because it has no seat. We could work on these issues and reach the first milestone relatively quickly. However, we are not going to do that. We are instead going to dive into the much bigger challenge of getting the tractor running. We’ll circle back to the brakes, seat, etc. once we’ve dealt with the other systems. So join us next time as we tear into the engine (which is seized). We don’t know what we’re going to find, but our experience with this tractor lets us predict that it won’t be pretty!

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FBN Network

Oct 10, 2019

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