'13 Ford rear axle housing straightening results so far

[nsbrassnut]

Hi All

I thought I would post a follow up progress report on the straightening of the rear axle housings for my ’13 project.

This note also ended up a bit long so again please bear with me. Hopefully you may find something of use buried in here somewhere.

Thanks to the notes and suggestions provided earlier I got over my hesitation to heat and cool the sides of the tube to work on straightening it. For mine, I decided to try the alignment jig on a bench with the dowel pin vertical and half housing bolted down on the base. Since ¾” drill rod is not terribly stiff I also modified my outer check tapered piece with a set screw so that it could be mounted just above the end of the housing tube. That way the housing would not “push” on the alignment dowel during the heating/cooling process.

I first tried my scrap housing to do some learning on. It started out about 0.100 inch off center. I heated the tube down near where the it starts to flair out to rivet on the center section. The idea being that working there would provide a slightly longer lever out to the end and therefore might provide a bit more movement at the outer end than would heating the middle of the tube. Similar to what was shown in the YouTube video of another person’s approach, I also wrapped some wet towels around the base and the outer end to try to slow any heat getting into the castings.

I’m a bit fire paranoid, so I only used a #3 tip for heating, not a cutting torch or rosebud tip. Those might work faster, but then I wasn’t in a rush. I noticed very quickly how spooky it is to see the tube first move in the wrong direction when the heat it applied. And then after applying the wet rag on the hot spot, watching and waiting and hoping for it to move back and then hopefully end up a bit in the right direction. It didn’t move much, but it did move in the right direction. It took about 5-6 heating and cooling cycles to get it very close to straight. Yea, success this may actually work after all!

I did learn the hard way that when you get very close, STOP and don’t always try for that last bit. I did that with one housing, got it very good in a few cycles and 20-25 minutes, then one more cycle and I overshot the target. It took another hour and a lot more cycles to get back to where I was.

I am please to say that eventually I was able to get 4 of the 5 housings back very close to straight. One of them is bent by almost ½” inch off center and I may have to use a more aggressive method on that one. I included some pictures at the end.

After trying out this method I would say that there is more than one way to get to a satisfactory result. I would rank the options like this for both simplicity and cost of materials and tools needed.

1) Assemble the regular rear differential in one housing and place the second one over the top (both vertically) as shown in the assembly guidelines. Then use the heating / cooling cycle until the bearing fits in. This will work, but I would also note that there is some “wobble” in the stock assembly which could result in the housings being “straight enough” but not really straight. This is similar to the method in the YouTube video Scott suggested. If you don’t have access to lathes and other stuff, this method could still provide a result likely as good as what left the factory in the first place.

2) Then get a long piece of PGS/drill rod the same size as the axle shaft (1 1/16” I think). Install the two inner bearing sleeves and roller bearings. Slide that in one housing through the bearing and then place the other housing on top and both the two together (no gasket). For this approach I would leave out both outer bearings. Then do the heating / cooling process and use the straight rod as an alignment guide. The drill rod is straighter than the two axles wobbling in the differential assembly, but the rod may still wobble a bit as it’s not always a tight fit in the bearings. Then heat and cool the housing until the drill rod is centered at the outer end(s). This is really little more than a variation of the first method. The idea being for the drill rod to hopefully provide a slightly better alignment guide.

3) Machine a bolt plate with center pilot and bored and fit a drill rod alignment guide (the approach I used here). Bolt on one housing section at a time and use the heat and cool cycle to straighten the tube until the rod shows it to be straightened.

4) You need access to a big lathe for this one. Machine a bolt plate with center pilot and mounting bolts (same as in 3) and leave it mounted on the lathe. Machine or find an alignment cone that mounts on the tail stock. Bolt one housing section on plate on the headstock. Heat the tube all the way around enough to soften the tube slightly (medium to bright red I think) and then use the tail stock to push in the alignment cone to straighten the tube. This may need a rose bud for heat, the welding tip that I used probably wouldn’t give out enough heat. Then allow it to cool naturally. This should keep it straight and do the alignment all in one step. I think this is what Erik described previously. Overall, this approach probably would provide the most accurate result. I think we are going to try this approach on the one really bent housing that I couldn’t make good progress on using the alignment guide.

Drive Safe

Jeff