Vibration STOPS when applying brakes

[redfishsc]

So here's a strange one. 1999 Suburban C1500. 230k miles.



Recently the truck developed a vibration starting about 45 mph. Kind of a moaning sound that got louder and more easily felt as speed increased. Feels like it's the front to me.

Front tires were getting old so I had them replaced, vibration went away for about a month.

Yesterday I hit a MILD bump in the road at 45mph (definitely not a hard hit) and the vibration instantly came back.

Oddly the vibration almost totally goes away when I'm braking. Not totally, but very noticeably.

Front has all new Moog ball joints, tie rod ends. Brake pads have maybe 12k miles on them. U-joints on the drive shaft have no play (i have not removed the shaft, just tried to jiggle it in place, it's solid in that regard).

Front wheel bearings are about 5yrs old, repacked about 2 yrs ago.

I haven't had a chance to jack it up since yesterday to inspect.

Any suggestions?

 

[SUBURBAN5]

I would try 2 things. Tug on both wheels for play possible bearings may have not been seated right 2 check your rotors for any usual wear. I know it doesn't shake when you apply the brakes but still double check the area.

 

[redfishsc]

You're right about the bearings and I'm going to check them again in the morning if this rain lets off, but I did check them as also did the tire place a month ago.

I need to look up the preload for the castle nut.

 

[SUBURBAN5]

Keep us posted. Also look at your motors mounts.. I doubt that's the issue but if worn they can move the engine quite a bit making it shake.

 

[redfishsc]

I think it was the passenger side inner bearing. The wheel had a TINY amount of play in it. Spinning the wheel by hand didn't tell me anything, sounded normal.

Yanked it all out and washed the bearings. Outer bearing still looked brand new. Outer bearing had the stuff you see in the pics. The camera REALLY makes them jump out, they're far harder to see in person.

All bearings still had plenty of grease but I had used a gray Valvoline Durablend which has moly. This time I'm using the Valv red high temp which should be more appropriate.

Bearings ordered. Nobody locally has a full set of anything but chinesium store brand bs.

Brakes are great, pads barely halfway worn (which is a couple years driving with my short commute).


Note : As mentioned above the pic really makes the wear spots really obvious. You can barely see them in person and you can't feel them.

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[Erik the Awful]

The way I was taught to do wheel bearings is to tighten them down snug, then back them off a flat (1/6 of a turn) or two. Every time I've done that I have play and vibration. I tighten down my wheel bearings and loosen them one flat. If I can feel any play, I tighten it one flat. Some people will say I have them too tight, but nothing has fallen apart yet. YMMV.

 

[redfishsc]

Got them swapped with some new Nationals, vibration gone.

I suspect I accidentally swapped the rotors though. Hopefully this isn't a problem lol. Truck brakes just fine but the first 6 miles smoked them up a little, and pulled to the right some when braking . I guess the two rotors/pad sides were worn slightly different.

Drives and brakes fine now though. Calipers and hoses are reasonably new, and I cleaned up the caliper slide bolts and slicked them up with fresh caliper grease.