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I recently figured out I had bent my rear axle housing (Ford 8.8 ) somehow. It started wearing the rear tires quite a bit faster than the fronts were wearing. When I started measuring I found the rear tires were toed in a full inch. That's measuring front vs. rear on a 35" tire.
Some of my attempts at straitening a housing were not so successful in the past. On the one's I managed to put enough force on the correct the problem, most bent again pretty quickly. From others reports of thier experience with straitened housings I gather this is a pretty common problem.
I decided to try something different. I've seen this done on equipment at work, but never on a axle housing. At this point I had little to lose - so why not try something.
The first step is to figure out exactly how the housing is bent. By measuring the distance across the tires I found where the tires were the furtherest apart. The widest point was at about 4:30 O'clock when looking at the drivers side tire.
My plan is to use heat to draw the axle back into alignment. Since I knew the longest side of the housing was at 4:30 I knew that is where the majority of the shrinking needed to happen. I installed 2 C clamps so that the screw was in direct line with the housing bend. One of the C clamps was a little longer than the other so I shimmed it to make it exactly the same length from the tube to the end of the screw. Then I filed a small groove in the end of the screw so a string would not slip off - then tied a masons line (really tough nylon string) across the two C clamps. This made a reference line so I could measure the amount of bend and location of bend.
The string is exactly 9.5" from the axle tube at the C clamps. I used a ruler to measure the distance all the way across and found it was only 9 5/16" right next to the drivers side of the differential. My first step was to weld the tube to the diff only on the side (bottom rear 1/3rd) I wanted to shrink. I welded it on both sides (drivers and passengers), but used a lot more heat on the drivers side. You can tell by the bulky weld that I camped out there for a while so the heat would soak in as much as possible.
The paint cooked off a good 2 inches from the weld so it was quite a bit of heat. This did a lot of good - the worst toe in was now 5/16" and still in the same plane - just needed more. I did some more measuring and now the worst measurement to the string was 9 7/16" and was located right behind the anti wrap bar bracket. I may have bent the tube when I welded the bracket on but I don't think so - the accellerated tire wear just started in the last couple of months. I'm more inclined to think the welding weakened the tube and stress bent it later.... but I don't know for sure.
About the only way I could figure out to bend it where I needed to is to weld something on the tube. First I had to weld the stock vent hole closed - you can see where I did that in the picture above.
Next I found a extra heavy 3" pipe nipple and started cutting it apart to make a 1/2 sleeve for the tube. Man I love my band saw!
Then I buffed a clean spot on the tube and welded the sleeve on.
I cranked the heat and wire speed up and took my time - heating the tube as much as possible without burning it too much. I did a single pass on both ends of the sleeve first and measured again. It had moved a little but not enough. I did the second pass - laying the bead between the first pass and the tube - again making a lot of heat on the tube.
This time it was perfect! 9.5" all the way across on the string, and exactly the same distance all the way around on the tires - not even a 16th of an inch difference. I'm pretty thrilled - this came out way better than I expected.
I rotated the tires and called it good. Pretty amazing what a little heat can do. I'm off to Utah to stress test it next month - I'll let you know if it does not hold up.
Tim :D
Some of my attempts at straitening a housing were not so successful in the past. On the one's I managed to put enough force on the correct the problem, most bent again pretty quickly. From others reports of thier experience with straitened housings I gather this is a pretty common problem.
I decided to try something different. I've seen this done on equipment at work, but never on a axle housing. At this point I had little to lose - so why not try something.
The first step is to figure out exactly how the housing is bent. By measuring the distance across the tires I found where the tires were the furtherest apart. The widest point was at about 4:30 O'clock when looking at the drivers side tire.
My plan is to use heat to draw the axle back into alignment. Since I knew the longest side of the housing was at 4:30 I knew that is where the majority of the shrinking needed to happen. I installed 2 C clamps so that the screw was in direct line with the housing bend. One of the C clamps was a little longer than the other so I shimmed it to make it exactly the same length from the tube to the end of the screw. Then I filed a small groove in the end of the screw so a string would not slip off - then tied a masons line (really tough nylon string) across the two C clamps. This made a reference line so I could measure the amount of bend and location of bend.
The string is exactly 9.5" from the axle tube at the C clamps. I used a ruler to measure the distance all the way across and found it was only 9 5/16" right next to the drivers side of the differential. My first step was to weld the tube to the diff only on the side (bottom rear 1/3rd) I wanted to shrink. I welded it on both sides (drivers and passengers), but used a lot more heat on the drivers side. You can tell by the bulky weld that I camped out there for a while so the heat would soak in as much as possible.
The paint cooked off a good 2 inches from the weld so it was quite a bit of heat. This did a lot of good - the worst toe in was now 5/16" and still in the same plane - just needed more. I did some more measuring and now the worst measurement to the string was 9 7/16" and was located right behind the anti wrap bar bracket. I may have bent the tube when I welded the bracket on but I don't think so - the accellerated tire wear just started in the last couple of months. I'm more inclined to think the welding weakened the tube and stress bent it later.... but I don't know for sure.
About the only way I could figure out to bend it where I needed to is to weld something on the tube. First I had to weld the stock vent hole closed - you can see where I did that in the picture above.
Next I found a extra heavy 3" pipe nipple and started cutting it apart to make a 1/2 sleeve for the tube. Man I love my band saw!
Then I buffed a clean spot on the tube and welded the sleeve on.
I cranked the heat and wire speed up and took my time - heating the tube as much as possible without burning it too much. I did a single pass on both ends of the sleeve first and measured again. It had moved a little but not enough. I did the second pass - laying the bead between the first pass and the tube - again making a lot of heat on the tube.
This time it was perfect! 9.5" all the way across on the string, and exactly the same distance all the way around on the tires - not even a 16th of an inch difference. I'm pretty thrilled - this came out way better than I expected.
I rotated the tires and called it good. Pretty amazing what a little heat can do. I'm off to Utah to stress test it next month - I'll let you know if it does not hold up.
Tim :D
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