There are just some days I wish I didn't turn wrenches

[OR VietVet]

By the way, the vibes are still in seat and floor board.

 

[iamdub]

My inspection of my girl's 1990 K2500 started at 9 am. First thing I did was decide to swap front and rear tires and while taking off the lug nut at a left rear stud, it came off harder than the rest. Ran a die down it with silicone grease as a lube and then used a tap with grease for the lug nut. Is a through nut because has the center cap held on with the plastic spin on lug nut covers. Put it all back together and after cleaning up the one stud with a wire brush and adding a dap on anti seize to all 24 studs and installing all covers and caps, went on a road test. Seemed to change slightly but vibes are still there between 45 and now 60 mph and now it seems to actually smooth a little with light acceleration. I played with the throttle and came to a conclusion that problem may be mounts or driveline related. Got home and up in the air again. Motor and transmission/transfer case mounts are rock solid. Used a large flat blade screwdriver and torqued on the u-joints and found absolutely no play. Then spun the driveshaft at idle and slight accel and is true as can be, no impact marks and no weights missing. every spring mount, suspension piece, steering piece and anything else that moves or holds something that moves, is tight and looks good. I believe it is gonna have to get worse before I can find the problem.

I am open to all insight to what this could be. I will likely go to sleep tonight thinking about it. I do that a lot.

Did you go through with swapping front and rear wheels?

 

[OR VietVet]

Did you go through with swapping front and rear wheels?

Read post #140.

 

[iamdub]

Read post #140.

I read it a few times before posting. I read it as you took the nuts off in process of rotating them then discovered the damaged lug thread, which you fixed, then put it back together as if to test if that one lug was the cause.

Checked runout on the axle flanges?

 

[OR VietVet]

I read it a few times before posting. I read it as you took the nuts off in process of rotating them then discovered the damaged lug thread, which you fixed, then put it back together as if to test if that one lug was the cause.

Checked runout on the axle flanges?

Sorry, should have been more clear. I fixed the wheel stud at the same time of doing the rotate/swap, front to rear and then experienced the slight difference of symptoms that I listed. Also, I inspected the wear patterns and for belt problems and found nothing obvious. I am going to air them all down a bit and road test and then back up to recommended air pressure and road test and 10 psi over recommended and road test. This problem is testing my diagnostic abilities.

I have not checked axle hub runout but will. That is something I have not considered. Thanks.

 

[iamdub]

Sorry, should have been more clear. I fixed the wheel stud at the same time of doing the rotate/swap, front to rear and then experienced the slight difference of symptoms that I listed. Also, I inspected the wear patterns and for belt problems and found nothing obvious. I am going to air them all down a bit and road test and then back up to recommended air pressure and road test and 10 psi over recommended and road test. This problem is testing my diagnostic abilities.

I have not checked axle hub runout but will. That is something I have not considered. Thanks.

Wanna know whats crazy (and stupid)? Tahoe Twin wrecked his Tahoe about a year ago. He slightly bent one of the 22" wheels- the black and machined ones I had on mine and sold to him. He had it fixed but always had a minor vibration and just assumed the wheel wasn't perfect. He played musical wheels a couple of times with only very minor changes in the vibes. I went to look at it and, during another wheel rotation, I noticed his rear rotor was wobbling. I only noticed it because of the slight on-and-off brake drag when I turned it. Pulled it apart and found the axle flange was bent. This fool didn't wanna bother with it cuz "the vibes didn't bother him" that much and just wanted it put back together. We ended up putting the bent wheel on the bent flange, but 180° "out of phase". So, they pretty much canceled each other out. Of course, the pulsating when braking still remained since the rotor was still wobbling.

He eventually found a new/used axle shaft and swapped it.

 

[OR VietVet]

The axle flange could be it and will check. The thing that gets me is the 45-55+ to 60 mph window of the vibes. When the flange was discovered on the Tahoe Twin, Tahoe, was it at all times and got worse as speed increased or was there a window like mine. Plus, these axles are in a K2500 semi float axle.

 

[NickTransmissions]

The axle flange could be it and will check. The thing that gets me is the 45-55+ to 60 mph window of the vibes. When the flange was discovered on the Tahoe Twin, Tahoe, was it at all times and got worse as speed increased or was there a window like mine. Plus, these axles are in a K2500 semi float axle.

Damn, surprised it wasn't an out-of-balance condition with one of the rear wheels as that's the only thing I know for sure will produce a vibration in a road speed window like that.

Does the vibration only happen upon acceleration or does it happen when loaded as well as coasting?

I'm assuming you have already checked but any play in any of the wheels to indicate possible worn axle bearing(s)?

 

[OR VietVet]

Damn, surprised it wasn't an out-of-balance condition with one of the rear wheels as that's the only thing I know for sure will produce a vibration in a road speed window like that.

Does the vibration only happen upon acceleration or does it happen when loaded as well as coasting?

I'm assuming you have already checked but any play in any of the wheels to indicate possible worn axle bearing(s)?

No looseness at wheel bearings, happens when in that mph window when accelerating, coasting and decelerating. Because it went from 45 mph to 55 mph and now 45 to 60 mph, after tire swap, I am still convinced it COULD be tire related and will try air up a little or down a little next and see what happens. I should have done this already but "forest for the trees" has kicked in. Back to basics, like I always preach. When I find the problem or have a different set of parameters, I will post here.

 

[Tahoe14]

Maybe try the road force balance and see if anything shows up.