Sunday, July 26, 2015

The Eighteen Hour Axle Swap

The following post contains a lot of technical talk, abstract photos of axle parts, and parts jargon involving axles. It might be clear as mud to some. Please leave questions in the comments box and I will do my best to clarify...

I did an axle swap on a 1971 Overlander one time. It took 20 minutes per axle to do the job. Complete elapsed time with set up and clean up was one hour. I have now also spent 18 hours swapping a single axle. How is that possible Frank? How could it possibly take that long? Man vs. welded on, bolted on, first generation torsion axle is how....

This is what the first version of the Duratorque axle looks like. When Airstream installed this bad boy in early 1961 they honestly thought this axle would never need service or repair. They sold it as an axle for life in their advertising that year.  It was installed as if it was never to come out. With exception of bearings and possibly one brake pad replacement, nothing has ever happened to this axle. Every single bolt was fuzed on. Every nut but two, had to be cut.

Normally the plate you are seeing is welded to the side of the frame rail. It is a separate piece. The axle tube slides into a notch and everything is bolted to the plate. In this application it was all one piece. It all bolts through the frame rails of the trailer. To make sure it would not come out, it was welded to the frame rails also.

When I first looked at this job, I knew I would have to cut a few welds. I honestly did not think it was going to  be a big deal. There is always something hidden. Never forget that. You may note three bolt holes. I thought it was only two. I could only see two. Once the two bolts were removed and the welds were cut, it should just drop out. Right? NOPE. There was a third bolt. It was completely hidden from me. I know you see it, but if the hub was still mounted, and the shock mount bracket still in place, you would not be able to see it at all. The shock mount bracket covered the hole perfectly. It was the same width and was only 1/8" from the frame rail. But, Frank! The Nut!?! Surely you could see the nut on the back side. Well, actually barely. It was so close to the cross member it completely blended right in. To get to the head of this bolt(screw). The hub had to come off(struggle) followed by the backing plate(struggle). The shock mount could then be cut free(struggle and only a brand new cutting wheel could reach in. After 10 seconds it was too deep and a new wheel had to be installed in the cut off grinder. I now have 15 slightly used cut off wheels).  

Unlike the other two bolts, this was a counter sunk machine screw. Like all the rest of the nuts and bolts on this trailer, it was fused together with rust. To get it out, I had to weld the head in place to keep it from spinning. The head is about 1 inch across and no slotted screw driver was holding that tight. The nut was so buried, we could only get about 1/8 a turn per set. The weld then had to be ground out to get the bolt out. 

So where are there welds? You are looking at the axle tube comining in from the right and the main frame rail is going off to the left corner. They welded angle brackets into place. Two on each side. As if three massive 5/8 bolts was not enough, they needed to weld it in too. Cutting these angle brackets was no big deal. Avoiding cutting the frame rail was.

So, all that old crap is gone. How are you going to mount the new axle in?

I had these plates cut from 1/4" steel by a computer guided plasma cutter. I bet ya these are a direct bolt on. The upper three slotted holes are to give an additional place to weld onto the frame. The verticle slotted holes are for the Dexter bracket spacing. The notch is cut for #4000 axle tube. I have these plates available for $200 + shipping and double axle configurations are possible also. These plates can be used to convert from leaf spring axles to torsion is desired(not what I recommend but something a lot of Airstreamers want to do).

Here you see the new mounting plate bolted to the axle mounting bracket. One shock mount has been welded to the torsion arm. The original, vertical shock mount has also been welded on to the mounting plate.

The entire assembly was then raised into place and aligned very carefully. The plate was then welded into place. Alignment was once again checked, brakes wired in, and it is done. Going forward, an axle swap on this trailer will be as normal as any. Well, except the holes will all line up and the shock will fit without a struggle.

I hope this made sense to one of you. I know it is rather technical and not all that pretty to look at. It is however far more important than zolatone colors and floor choices. Please, if you have any questions or concerns leave me a comment. If you comment about your Ray Ban sunglasses, your God who hates everyone but you, and or your heating and air conditioning company I hope your computer becomes infected. Everyone else, thank you for reading.


  1. Frank, I am looking at replacing my 1964 Ambassador axles next spring. The axles in this post look very much like mine except I see no bolts in mine all I see is welds. Question where the brakes in this trailer electric of hydraulic. My trailer at some time had hydraulic and someone switched them to electric. They left the flex hose behind the backing plates where the come through the frame and the pipe at the front of the trailer where propane tanks are. Question How do you measure placement of axle to trailer. What are your thoughts of placing support between new axle and frame( trying to gain some height off the ground.)

  2. First I must say I am not a big fan of the high rider look. I think it seriously changes the look of the trailer. If you need more clearance I recommend you go with a higher start angle. The hostess you describe are new to me. I have not encountered that yet. I might suggest a look at the Dexter web site. They have a very good section on what to measure and where. You are most likely, 58 bracket to bracket, 75 hub face to hub face. Reverse bracket, electric brakes, easy lube bearings. If it were me I would do #3700 each.