Thread: How did this happen?!?! Broke right front half shaft on 81' SIII 109 Military 6-pot

Originally Posted by Tins

Can you give us a bit of history? I mean, is this a new to you car? Could it have been put together incorrectly by a PO, or are you doing maintenance or renewal on a car you have had and driven before? I'm struggling to get my head around that video unless there's a component that is wrong.

This is a former Australian military truck that I restored. Everything except the normal maintenance items like the seals and bearing associated with the wheels. I did a quick check on this and looked for any movement and all was fine.

restored the truck and have put at least 5,000 miles on it. Decided I wanted to replace and refresh all the wheel bearings seals and gaskets since I was starting to drive this vehicle more. Just wanted to know they were new.

disassembled both sides and replaced seals and bearings. The swivel balls and housings were fine. So I left them. Upon reassembly the right side starts eating axles. See the previous write up and pics.

it has to be something with the swivel bearing on that lower side unless the former owners simply adjust the height of the swivel housing by tightening or loosening the lower steering arm bolts and the upper pin bolts.

I’ve compared the bearings in the lower swivel ball and they are the same - the new one and the old one. At this point, I’m wondering if I simply didn’t notice a “fix” that had been done when I disassembled it?!?! But even then I would think I would have noticed something weird in the steering of the truck.

I did flip the swivel housing around and the bottom taper bearing fits nicely then. But that isn’t the answer since the face of the swivel housing will not be perpendicular to the ground if installed that way.

I haven’t found that there are two different types of taper bearings. Both the old and the one have the exact same numbers on them. And nowhere online have I found options for a different taper bearing. 🤔😞

I wonder if the ball had at some time had the lower swivel seat* re-machined, and a spacer fitted (perhaps reconditioned in service), which you failed to note and preserve on reassembly?

*Alternatively, the same could apply to the machined flat for the steering arm on the bottom of the swivel housing. There may have been shims here, and since the shims would be the same as the ones on top, this is possibly more likely.

I have jus taken some photos of a military ball and housing assembled that I have out the back. I don’t know what to say about this but when assembled correctly this is how it looks the ball is machined with the bearings off set to give you king pin inclination. So when assembled the housing back looks to be misaligned to the ball mounting surface. Then the stub mounting surface is perpendicular. If you have the ball mounted on the axle housing and when looking side on the bearing hole at the top is further in than the bottom hole it is mounted correctly. So if you do and it’s misaligned when you attach the stub axle housing as John says there has to have been some modification to original. This is a very interesting subject to ponder but not enjoyable for you I am sure. Good luck with it.
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Update:

I was following some advice previously provided by several of you all and began disassembling the left side since it was also torn down like the right side. As a reminder, on both sides, initially, I only replaced the seal in the axle and reused everything else since it looked rather new.

Upon inspection of the right side, I noticed that the studs that are supposed to be used to hold the top swivel pin in place, were actually bolts instead of studs. They studs were holding the steering arm on. Basically reversed from the left side, which is correct according to the workshop manual. The correct method per the workshop manual is to have the studs hold the top swivel pin in place and the bolts are used on the bottom to hold the steering arm to the lower swivel housing. I made the switch, assembled the swivel ball, swivel housing, half shaft, spindle/stub axle, hub, brake and drive flange and installed as one piece. I did this so that the weight of the swivel ball and housing wouldn't affect the seating of the lower tapered bearing. I did tighten the lower bolts (previous studs) securing the steering arm but left the top swivel housing pin studs with loose nuts on them. So at this point, I have on my workbench a complete swivel housing (swivel ball, swivel housing with top pin and lower tapered bearing and steering arm), half shaft, spindle/stub axle, complete hub and drive flange and a half shaft that rotates freely in the track bearing. And no apparent binding of the half shaft, on the inner spindle/stub axle, while the swivel housing is situated so that the lower swivel taper bearing is seated in the bearing race like it will be when the weigh of the truck is pressing down on the swivel housing/ball assembly.

I installed this until and tighten the swivel ball flange to the axle flange. So at this point, I know that the drive flange and the track bearing are holding the half shaft in proper alignment with the opening in the spindle/stub axle. In other words, there isn't any binding of the half shaft to the inner of the spindle/stub axle.

I tighten the top pin bolts securing it to the top of the swivel housing. The difference here is that previously, I had installed the swivel ball and everything else up to the drive flange separately in situ. This time when I tightened the top pin bolts, which did indeed move the angle of the swivel housing outer face, but not like it had in the previous times when I had tightened the swivel housing top pin bolts (now studs) prior to securing the drive flange to the hub. I point this out because previously when I had begun to tighten the swivel housing top pin bolts, the normal 90 degree angle between the swivel housing outer face and the ground would change so that the lower face of the swivel housing would be further out toward the tire than the top....which was causing the spindle/stub axle and half shaft to bind immediately.

I know what you're thinking.... that if there was binding before when you tightened the top pin bolts so the binding forces have had to go somewhere else, right?!?!? Well, I don't know yet. I only had a chance to run a few tests.

While still on axle stands, I placed the truck in 4x4 high, scotched the left front wheel to keep from spinning to force the right wheel to spin. I took temp readings of the drive flange, visible part of the half shaft sticking through the drive flange and the small visible cross section of the spindle/stub axle flange secured against the swivel housing inner face. I ran the truck for a kilometer in fourth gear getting the speed to about 45-50 km/h. The temps stayed the same.

I then took the truck off the axle stands and drove the truck up and back on my driveway and through my front yard into my backyard and stopped to measure temps and they were the same. Felt no heat around the drive flange.

I hope tomorrow early in the AM before all the traffic hits the streets to drive her down the road at speed and see what happens. Will report back with more data and hopefully good news and a video or two.