Project Super C, Mission: Transmission, Part 2
This is the third 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 this series, please start with the introduction to the project in our first post.
When we left off, we had drained several gallons of water and oil sludge from the seized rear end of the tractor and had refilled it with diesel fuel to help cut the remaining sludge and dissolve rust. This week, we’re going to finally find out the state of the transmission and gears, and in particular determine whether the rear end is seized due to catastrophic rust damage.
To get at the transmission and gears, we need to open the transmission case. After removing the bolts holding on the transmission case lid (two of which are hidden underneath the instrument housing), we removed the lid and set it aside.
With the lid removed, the moment of truth had arrived. Here’s what we saw:
At first glance, there’s definitely some rust, but it could be much much worse! The transmission gears at the right of the picture don’t look great though. Let’s take a closer look:
That rust doesn’t look pretty, but it is not structural and we’ll be able to clean it up. The gears that are visible actually seem to be in pretty decent condition. So far so good! However, we still don’t know why the rear end is seized - maybe some of the gears in the lower part of the transmission case are rusted, broken, or jammed. In order to get a good look at those gears, we are going to need to raise the rear of the tractor up on jacks, manually manipulate the transmission gears to put the transmission into neutral, and then hand-rotate the rear wheels which will in turn cause the gears to rotate into view. These illustrations will help explain:
As you can see, each rear wheel is connected to a large “bull gear” which is connected to the differential gears (by way of the bull pinion gears), which are in turn meshed with the bevel drive gear, which is driven by the lower transmission shaft, whose various gears mesh with the gears of the upper transmission shaft depending on what gear is selected by the shift lever. The upper transmission shaft is connected to the drive shaft, which is connected to the engine by way of the clutch. In this way, power flows from the engine to the rear wheels. We will be “driving” the system of gears backwards by rotating the wheels directly.
Upon jacking up the tractor (as seen below), we were able to rotate each wheel in turn and get a good look at all of the parts of the gears. Amazingly, they look OK! No teeth seem to be missing or damaged, and all rust is minor. How is this possible? At least some parts of these gears were immersed in water for years - shouldn’t they be badly rusted? While we don’t know for certain, we suspect that the layer of oil sludge floating above the water (as described in our prior post) formed an insulating layer that blocked additional oxygen from readily reaching the water from the outside. This would slow the rusting process by depriving it of oxygen.
In addition to revealing the state of the gears, this experiment showed us that when in neutral, the rear wheels rotate freely. This is great news as it means that, given enough work, the tractor should at minimum be able to roll again (which is our first major project goal).
Not all of the news is good though. We tried manually moving the transmission gears to put it into gear, and then depressed the clutch pedal. As you can see from the earlier illustrations, depressing the clutch decouples everything aft of it from the (seized) engine, which should then let us rotate the rear tires even though the transmission is no longer in neutral. However, we could not move the tires - we were fighting against the seized engine. This tells us that the clutch is not working - another thing we’ll need to investigate!
With these discoveries, the mystery of the seized rear end is partially solved: there was no way to decouple the rear wheels from the seized engine because we couldn’t get into neutral (the gear shifter was and is stuck in first gear) and the clutch doesn’t work. But we don’t yet know why the gear shifter is stuck - join us next time where we’ll investigate that.
In the next post, we figure out why the shifter is stuck! In the next post, we figure out why the shifter is stuck!
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