Fun with vibrations

[4x4_Welder]

Well, not really. I picked up an 85 Suburban K10 with the 6.2 diesel for a quite good price, but it has a vibration issue. It feels like a u-joint going out, but new u-joints didn't fix it (BTW, the designer of this thing needs a swift kick to the nuts, you can't grease the universals once installed). It's primarily at 62-70mph, I haven't taken it faster than that as I don't dare to and I don't think it can do it anyways. The auto hubs do unlock, the pinion bearing has no play, no odd noises, but there is some play in the t-case output. I don't really know how much is too much though, it doesn't feel like a whole lot and the seal isn't leaking. There isn't a leak, and the t-case brace is firmly bolted in place so I'm thinking the trans-transfer case adapter isn't cracked. There aren't any obvious dents or missing weights off the driveshaft either. I do need to get this thing highway-worthy, so if anyone has a thought I would appreciate it.

 

[Chevycrew]

Stock or lifted? Tire balance?

 

[4x4_Welder]

About 2" lift, it doesn't feel like a tire though, it's a fast vibration.

 

[lpurcell]

Are your u-joints indext. i mean ,look too see if the slip joint did not get a splin or two off,it will make a big differance.

 

[krany]

Are your u-joints indext. i mean ,look too see if the slip joint did not get a splin or two off,it will make a big differance.

i will second this, it will make a good noticeable vibration when they are not all aligned.

 

[4x4_Welder]

Well, this one is a slip yoke so that's factory set. No visible dents or obvious missing weights.
I think I may have the driveshaft balanced, there's a driveshaft shop literally right around the corner from me.
One thing that concerns me is the amount of slop between the yoke and t-case output, the seal isn't leaking and the case looks newer, but I can move the driveshaft around a bit, maybe .010-.015". I don't know how much play is too much, though.

 

[Cascadia]

I drove my Tundra to Cali and back this last week. It drove smooth most of the time but there were a few times going aroun 75-80 that there was a slight wobble. It never did it at slow speeds and it was a fast wobble like you are describing. When I got back I got my tires rotated and balanced (they already were though) and they said they took quite a bit of weight and it drives completely smooth now with wobble or vibrations.

 

[4x4_Welder]

I really don't think it's tires, but I do have another set of 31s on six lug rims that I could try on it.
The lift is a Rough Country, at leas that's what the back window sticker says.
It may be more than 2":

The pinion angle is within a degree or two of the driveshaft, and the slip yoke doesn't seem to be out too far.