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Discussion Starter #1
I have a new problem with my '29 highboy. When I leave my drive it seems fine but when I get up to some speed (more than 20) I get a rattling that feels almost structural, as if the axle is loose or something.

I checked and everything seems tight except the U-bolts where the driveshaft meets the axle which I tightened.

I checked the oil level in the axle which was mysteriously low and 'foamy'. I added a pint which still didn't quite bring it to full. Does this foamy look mean something?

So, any ideas on what might cause this?

The suspension seems tight and it came on gradually. For a day I was able to drive it up to 30 before I got the rattling (and only after 5-10 minutes) and by the following day the rattling is happening down at lower speeds and prety much immediately.

I am even not sure what axle I have so any help in that direction would be appreciated. Pictures below...

Thanks,
Paul



 

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the rear is a ford 8 inch and the oil shouldn't be foamy. i'd drain it and refill it.

can you post a pic of how the two bars coming from a the rearend hook to the frame.
 

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Discussion Starter #3
Thanks for the note. Do these show what you are after? Bear in mind it has been working fine and has suddenly gotten this problem so I think the configuration is fine.

Thanks,
Paul



 

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If you look at your rear u-joint you will see it is not in there straight. Look at the picture, the upper u-bolt is flush with the end of the cup and the lower has what looks like 1/4" of cup sticking out. This puts the knuckle of the driveshaft rear yoke right close to the yoke of the rear end and I'm betting that may be your rattling. Correct the alignment by loosening the u-bolts and aligning the cups correctly, then check and see if there are any shiny spots on the yoke indicating contact.
 

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Nothing to do with the rattle but it IS advisable to have jam nuts on all tie rod ends, spherical rod ends(Heim joints), and bushed eye ends that are used on radius rods and drag links. If you don't use jam nuts the threads in the bar and on the end can work and eventually the threads will be hammered out and the link will be loose and unrepairable. Evident by red dust at the connection.
It may be a optical camera angle thing, but check the distance between the bars from front to back on the rear end. The right hand bar setup looks like it is closer together at the front than the back. Parallel link suspension should have parallel bars.
 

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Oh, one more thing. If you expect to be driving this car for more than a few years in all kinds of weather, I'd recommend pulling those plywood floorboards out and treating them with some good wood preservative, then a nice coat of black paint, rattlecan is fine, just cover up that woodgrain.
 

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I agree about your u-joint. If that doesn't solve your problem, you may want to put it up on jack stands and, with it running, look under (don't get under) and see if you can spot a problem, like the drive shaft jumping around. May need someone to accelerate it in gear while you look.
 

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U-joints

Looks Like The Cap Was Not Seated Correctly In The Yoke. That Will Deffinately Cause A Vibration Aabove 25 Mph.
 

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Discussion Starter #10
Wow, some good replies, thanks guys.

I will have a look at it in the morning. It might be worth replacing the bearing caps whilst I am replacing the oil in the axle.

Oh, and replacing the plywood is a great idea. The problem is that every time I go out to the garage to do something on the car I end up driving it instead! Supposed to be mid to high 70's this weekend so you can see the problem! ;-)

All input appreciated, thanks again. I will update this thread when I have a look at it.

Paul
 

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Discussion Starter #11
OK, I had a look and straightened out the caps and U-bolts. Problem still there.

I put the rear of the car in the air as was suggested in one post. It sounded pretty quiet UNTIL I cut the engine and then I could plainly hear the gears in the axle. Almost as if there were dry. I rotated one wheel clockwise expecting to see the other rotate counter clockwise and it did once or twice but several times it just sat there and did nothing. Is this indicative of something?

I am starting to think the axle is fried.
 
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