strange shimmy

[Blue_71]

i know this is the wrong board but im gonna try to fix this tomarow so i wanted to post it here where it'd be seen.
drove my dads 94 k3500 dually on a long trip... had a major shaking / vibration in the rear drive train... doin good to hold it steady at 55, sometimes 65... This morning we found the rear outer tire had a busted valve stem - had the tire fixed at a wal mart-- and got back on the interstat, and it is still doing the same thing. its not AS bad, but still major vibration at 65 and up -

i checked the carrier bearing and it has alot of play in it. would that cause a shake like that? it doesnt show up untill at least 55, and isnt bad untill 65. how long would it take to fix the carrier bearing?
Thanks~

[walker]

Seems to me those had composite drive shafts that were prone to going bad. They go bad at the union between the yoke and the shaft I think.

[Huck]

Josh, check the composit to metal connection at each yoke on the rear drive shaft by pulling on the shaft real good----any play is not good. If the carrier bearing is letting the driveshaft slop around---that could also be the problem. I usually have the carrier bearing changed at a parts store that can do that as they usually have to be pressed on/off and I didn't have a large/long enough press to do that.
At speed --55-65 if you shift into neutral, does the noise go away? Can you jack the truck up SAFELY at the rear axel and then run the sucker----you can sometimes see/hear what is going wrong---bad tire, bad axel bearing, bent drive shaft, spring mount, shock mount, etc.

[Baradium]

Good be as simple as a bad u-joint... that carrier bearing could be it too though. Either way, if the carrier bearing is bad, you need to replace it... you can do some carrier bearings at home, but I don't know about that one.