I have finally concluded the repair of my 1992 Ford F-250's steering system. I say "repair" but "replacement" is a more honest description, as I have replaced everything but the intermediate shaft. I find it interesting that this component is in such apparently good shape (it slides and rotates without any sound or feeling of friction) when everything else in the system was shot, especially since several Diesel Stop members have complained about its failure.
The steering system in this vehicle is nothing to be particularly proud of. It uses a rack and pinion steering box with a pitman arm, the same Ford C-II steering pump that Ford put in virtually everything, and a Y-type steering linkage which produces bump steer, specially when lifted. Luckily this tendency is not too bad, or mixed with the dogtracking effect of having axles of two different lengths it would produce a vehicle that was very annoying to drive. As it is, you spend a great deal of time accounting for dogtracking while driving on roads whose camber changes frequently.
However, now that the steering system has been almost entirely replaced or rebuilt — the box and pump replaced, the column rebuilt — there certainly is a new joy to driving. When I first got the truck it still steered fairly smoothly, but it's far and away nicer now. Just as wonderfully, there are zero leaks in the steering system; I was beyond tired of spewing ATF onto the ground.
Attempting to rebuild the steering pump was what we call a bad idea. As far as I could tell from the diagrams in the factory service manual (I referred to both the electronic and paper editions) I performed the job correctly, yet the pump did not produce any pressure when installed. The replacement functions just fine, with the only difficult part of the job being replacing the teflon seal on the end of the high pressure line where it connects to the pump. I bought the pump without reservoir, which is feasible since I own a vise. The high pressure fitting is pulled out of the side of the pump, a large O-Ring lubricated with fluid (In this case, ordinary Merc/Dex ATF) and installed, the fiberglass reservoir pressed on by hand, and the fitting reinstalled and torqued to 20-30 ft-lb, IIRC. I usually shoot for the middle in these situations, and so far, so good. You save a whole dollar by buying it without the reservoir, but I was feeling testy at that point and wanted to feel like I had done something.
As for the aforementioned Teflon Seal, it is like an O-Ring but made of white teflon and with a square rather than round extrusion. I ended up just installing it like an O-Ring, which is to say with a seal pick. The manual instructs that you should stretch it over a taper and that it will slowly return to size, but in my experience it returns rather quickly to size, and if you actually stretch it large enough to slip over the threads then it will never recover. I stretch the seal very slightly, then install it like any O-Ring. Teflon is pretty squishy and if you scrape the seal up a little bit then it's no big deal. If it contracts down onto the threads then run your pick around the thread with the point of it way down into the thread form, and sort of screw it down. The seal will jump down there and work fine so long as you don't poke a hole in it. There is no torque spec given for the connector, so just snug it down until it bottoms out and then stop. The line is sealed at the flare nut with the teflon seal and between the line and the nut with an O-Ring; if this O-Ring fails you are supposed to throw the line away and buy another one.
As further evidence that I am not perfect, after the installation my speedometer and odometer did not work. I went so far as to pull the cluster before I discovered that in my genius I had failed to fully tighten the 7mm-headed screw in the middle of the ignition switch connector. This turned out to be a boon, however, because for whatever reason when I got everything back together my cruise control worked for the first time. I had been worried I'd have to disassemble and reflow the solder on the speed control module, so this was an especially welcome discovery.
While bits of the dash were out, I also took the opportunity to change my digital pyrometer's wiring to draw power from the radio wiring by splicing it with some 3M snap connectors I had lying around, behind the dashboard where it doesn't interfere with the actual wiring to the radio. The pyro wires are zip tied to the warning light cluster wires; since a thermocouple is a voltage-generating sensor there's no particular risk of noise being brought into the stereo wiring unless a noisy signal is run parallel to the thermocouple wire in the engine compartment, which is not currently the case. Now I can use my illumination dimmer again; the Auber 1813 needs nearly 12 volts to operate and I formerly had it wired into the dimmer circuit because it was already tapped for gauge lighting. I have yet to backlight the filter minder, but it is not particularly critical. This really has been a nice little gauge, and I'm not even using its more interesting features. In particular, since it has an internal relay switched from a controllable set point, it would make a dandy controller for water injection. Now, if I could just find a suitable pump...