Rear bearings, '70 bus.
Posted: Tue Jul 01, 2014 11:53 pm
So I noticed on our last run on the new engine down to Eugene, Corvallis, Tangent, Willamette valley farmlands, that I had a bearing thrum/hum noise most disconcerting that hasn't diminished since.
My initial response was to inspect the front end. But after tearing down and repacking, nothing really scary there, ancient bearings, a dent in the cage of one outer bearing, but nothing drastic looking. And the noise was still there.
Next suspect, CVs. But then, listening to it riding home from the Lab last Monday, I had an epiphany. Rear wheel bearings, the ones I replaced (no confidence in my abilities) in an effort to address diminishing rear hub tolerances expressed by drums scraping against brake backing plates.
While cleaning and repacking the front wheel bearings, brake shoes looked due. So Sunday I worked the front wheels with new brake shoes and gentle love.
Monday I began the brake job on the rear wheels. Sure enough, the suspect wheel axle nut about spun off by hand after removing the cotter pin. The driver's side wasn't.
Gee, maybe if I just brought the assembly up to torque spec, my bearing thrum/hum noise would be abated. But no, I couldn't let it go and broke it open anyway, without even testing the simple solution. The backing plate would not come off. Finally gave up and got the axle stub and bearings out. Those C-clips are a bear.
Today, reassembled. Eh, I cleaned 'em up and put 'em back in, with new seals. But was willing to reuse the old ones because they came out pretty easy with the seal puller tool. Kinda like the front bearings. Nothing damning. Must have been the loose torque on the wheel/drum. Doh!
Oh, yes, have some photos. Because this tolerance drum scraping brake backing plate issue has been chased and chased. Beyond the stock elements, is an extra "spacer" (big ass flat washer) between the drum and the stock outer spacer. The torque spec tends to compress the spacer components that are of course made of unobtainium now. No replacements available. Haven't got into the other wheel yet. I'd actually forgotten the spacer was there. I even have spanking low mileage drums with splining that's still not being hammered away into slop, and no loss of spec from compression.
I specced the pads, and they were down 2 mm at the worst from the 8 mm of the new ones. Three years on. But not pretty.
New brakes good.
Here's my extra great big washer spacer. It concaved a bit, and yep, compressed, notice the ridge in the center.
Here's the inner flat surface of the outside spacer that mates with the inner race of the outer bearing assembly. Looked pretty flat, but you can see the lip on the inside in the photo that says, yep, compressed and thinner than it used to be. The beveled edge was against my extra spacer washer, and looked just fine. My extra spacer seemed to mate with the beveled side, so pretty sure this was the face against the inner race of the outer bearing.
And here's the face of inner race of the outer bearing. The other side rests against the inner spacer and looked better. The damage looks much worse in the photos, but still far from pristine just exactly perfect.
Here's the outer race of the outer bearing which I left in place and did not remove. Discolored, but no real rut discernible by fingernail. You had to want to feel it, maybe, just barely, sorta.
And one of the edges of the inner spacer. The other side was just as bad. Stock. I don't recall doing anything three years ago when I put the new bearings in. But notice the hammered in edge with the sharp lip. Thus the issue.
Of course the bearing surfaces of my axle stub were again, less than shiny and new. Here's where the outer bearing rides.
And the surface where the inner bearing of the axle stub lives.
So yep, cleaned, re-greased, put it back together. Used new grease seals, had new bearings, but didn't go there. Tomorrow, the axle back on and the brakes on both rear wheels because it's getting hot and the campers need a ride down to the reservoir for their afternoon swim. After today, they're miffed. They wanted it Monday.
I did take the harsh edges off the ridges of the extra spacer and inner spacer with a small file, but didn't flatten them. The brake backing plate did not want to be removed from the bottom dowel. Two days of PB Blaster and repeated efforts from the back with hammer and punch, thought I might be making progress, but it might have only been the deformation dimple in the backing plate the punch seemed to be doing. Didn't really need to take it off anyway. Came off three years ago, though.
Please call me on anything in case my assessment is flirting with disaster and things are direr than I suspect, and thank you for your patience.
neal
My initial response was to inspect the front end. But after tearing down and repacking, nothing really scary there, ancient bearings, a dent in the cage of one outer bearing, but nothing drastic looking. And the noise was still there.
Next suspect, CVs. But then, listening to it riding home from the Lab last Monday, I had an epiphany. Rear wheel bearings, the ones I replaced (no confidence in my abilities) in an effort to address diminishing rear hub tolerances expressed by drums scraping against brake backing plates.
While cleaning and repacking the front wheel bearings, brake shoes looked due. So Sunday I worked the front wheels with new brake shoes and gentle love.
Monday I began the brake job on the rear wheels. Sure enough, the suspect wheel axle nut about spun off by hand after removing the cotter pin. The driver's side wasn't.
Gee, maybe if I just brought the assembly up to torque spec, my bearing thrum/hum noise would be abated. But no, I couldn't let it go and broke it open anyway, without even testing the simple solution. The backing plate would not come off. Finally gave up and got the axle stub and bearings out. Those C-clips are a bear.
Today, reassembled. Eh, I cleaned 'em up and put 'em back in, with new seals. But was willing to reuse the old ones because they came out pretty easy with the seal puller tool. Kinda like the front bearings. Nothing damning. Must have been the loose torque on the wheel/drum. Doh!
Oh, yes, have some photos. Because this tolerance drum scraping brake backing plate issue has been chased and chased. Beyond the stock elements, is an extra "spacer" (big ass flat washer) between the drum and the stock outer spacer. The torque spec tends to compress the spacer components that are of course made of unobtainium now. No replacements available. Haven't got into the other wheel yet. I'd actually forgotten the spacer was there. I even have spanking low mileage drums with splining that's still not being hammered away into slop, and no loss of spec from compression.
I specced the pads, and they were down 2 mm at the worst from the 8 mm of the new ones. Three years on. But not pretty.
New brakes good.
Here's my extra great big washer spacer. It concaved a bit, and yep, compressed, notice the ridge in the center.
Here's the inner flat surface of the outside spacer that mates with the inner race of the outer bearing assembly. Looked pretty flat, but you can see the lip on the inside in the photo that says, yep, compressed and thinner than it used to be. The beveled edge was against my extra spacer washer, and looked just fine. My extra spacer seemed to mate with the beveled side, so pretty sure this was the face against the inner race of the outer bearing.
And here's the face of inner race of the outer bearing. The other side rests against the inner spacer and looked better. The damage looks much worse in the photos, but still far from pristine just exactly perfect.
Here's the outer race of the outer bearing which I left in place and did not remove. Discolored, but no real rut discernible by fingernail. You had to want to feel it, maybe, just barely, sorta.
And one of the edges of the inner spacer. The other side was just as bad. Stock. I don't recall doing anything three years ago when I put the new bearings in. But notice the hammered in edge with the sharp lip. Thus the issue.
Of course the bearing surfaces of my axle stub were again, less than shiny and new. Here's where the outer bearing rides.
And the surface where the inner bearing of the axle stub lives.
So yep, cleaned, re-greased, put it back together. Used new grease seals, had new bearings, but didn't go there. Tomorrow, the axle back on and the brakes on both rear wheels because it's getting hot and the campers need a ride down to the reservoir for their afternoon swim. After today, they're miffed. They wanted it Monday.
I did take the harsh edges off the ridges of the extra spacer and inner spacer with a small file, but didn't flatten them. The brake backing plate did not want to be removed from the bottom dowel. Two days of PB Blaster and repeated efforts from the back with hammer and punch, thought I might be making progress, but it might have only been the deformation dimple in the backing plate the punch seemed to be doing. Didn't really need to take it off anyway. Came off three years ago, though.
Please call me on anything in case my assessment is flirting with disaster and things are direr than I suspect, and thank you for your patience.
neal