Note: this is a continuation of an article started in Notes Vol. 66.
To link to that article, Click Here
Repairing the Work Truck
keeping the equipment working
It's cold out there with daytime temps in the teens, so for the most part it's a good time to stick close to the wood stove and attend to inside stuff, but our life here is so interwoven with life outside that I can only stand staying inside for so long before I go find something outside to attend to. Now that the ground is frozen hard, it's not a bad time to do a bit more work on the truck--lying on the hard frozen ground is certainly better than lying down in the slush.
unbolting the rear axles
using a wrecking bar to hold the wheel hub stationary
Before we can get in there and remove the old ring gear, the axles need to be retracted. To do that, they have to be unbolted from the ends of the hubs. One of the reasons that people go to the trouble of keeping these old 3/4 ton Chevys running is that they're designed to carry heavy loads, and this heavy-duty arrangement for the rear axles is part of that rugged design.
There are eight heavy bolts that connect the axle to the wheel hub, and ten minutes with a heavy star wrench is enough to free the axles. One point to remember; it's always a good idea to use lots of separate coffee cans to hold the various bolts. If you dump all the bolts into one can, then you have to make sure that you use the right bolt in the right place when you reassemble. By keeping all the axle bolts separate from the other 1/2 inch bolts, we're less likely to get confused with it comes time to reassemble, a point that's especially relevant when doing work over a period of time like we are here.
the rear axles retracted from the hubs
With spring just around the corner, it's past time to get the work truck repaired and back on line, and I have to confess that it's been more than just the snow and muck that's been keeping me from getting under the truck. When I notice that I'm shying away from a task, it's time to take stock and see what it is about the task that's holding me back.
Upon reflection, I can see that it's the challenge of reassembling the housing that holds the pinon that's got me rattled. It's a complex piece of work that involves two sets of counter-facing bearings (each of which consists of an inner and outer race that have to be hydraulically pressed into place) separated by what's called a "crush sleeve" In order for the bearings to do their job, they have to be stressed against each other to just the right degree: too little and they'll rattle around and wear, too much and they'll overheat and fail. The idea behind the crush sleeve is that if they're preloaded too much, the crush sleeve will give way enough to take some of the strain off the bearings.
Here's a pic I found of a pinion gear (that's the slanted gear on the right end of the assembly) with the bearings mounted in the correct order. The bearings actually seat in a cast iron housing which is missing here so that you can see the bearings.
In order to preload the bearing just right, you need a special sort of torque wrench, and while my usual response would be to go out and purchase the speciality tool, in this case I elected to haul the whole assembly into a professional and have him do this part of the work. We ask this truck to do some very heavy work such as hauling loads of rock up the 1,200' grade from the river to Windward, and having gone through the expense of replacing the ring/pinion set and all the associated bearings, I really don't want to have to do this again. Sometimes you just need to tell your pride to go sit in the corner so that a pro can handle the situation right the first time.
Done right, the repair we're doing will last another quarter million miles--done wrong, all bets are off. And one of the reasons for keeping this rig on line is that they just don't make heavy pickup trucks like this any more. I'll pick up the pinion assembly next time we're in The Dalles, and I have a clear understanding of how to proceed from there. The pinion assembly will need to be shimmed so that it engages the ring gear just right, but that's a matter of install, check and add or remove shims as needed--tedious, but straight forward.
It's been a while since there's been any progress to report on the work truck. The hang-up involved finding someone who was familiar with the process involved in pre-loading the bearings. Our work truck is a 1980, and that's great in that trucks in those days were rugged built and capable of doing heavy work if you take care of them, but the down side involved finding a specialist who knew how to put just the right amount of pre-load on the opposed bearing set. That involved the judicious use of a 20 ton hydraulic press and a high powered torque wrench--I figured out early on that the task was beyond my skill set. Sadly, my efforts to find someone nearby who was up to the task weren't successful either.
I eventually figured out that I'd have to take the pinion assembly to Portland; it was four hours of driving for a bit of work that took about fifteen minutes, but what a difference it makes when someone has the right tools and know-how. The long drive there and back was time well invested.
Here's a side-by-side pic of the old, failed pinion, and the new pinon assembly ready to bolt back into the differential housing. There's some messy work that needs doing before that happens, but that will be almost a relief to do now that I'm confident that the assembly is right.
Repairing the work truck has been a journey into mechanical archania and the subtle workings of differentials and split axles, of loaded bearings and magnetic washers. Given the importance of getting this right, the plan has been to slowly and steadily focus on each component, figuring out what it does and what it needs, and then moving on to the next bit. In time, the puzzle of what each bit was and what it did resolved itself, and I'm pleased to report that the rear-end is back together to the point where everything appears to be working. So much so that today I was able to remount the wheels and drive the truck across the work yard under it's own power.
The piece of plywood is roughly where the rear axle spent the winter, so while the relocation of the truck may not seem like much to be excited about, it's an achievement that I take great pleasure in.
There's still a good deal of work to be done as the differential is sealed up, filled with heavy weight oil and the process of "breaking in" the new gears is begun. After a short run down to Klickitat and back, I'll drain the oil, pull the rear cover, retorque the bolts, check the play, and anything else I can think of before getting close to feeling that the job is finally done, but still, getting the work truck moving under it's own power again is a very good thing.
Notes From Windward - Index - Vol. 67