Help me troubleshoot a vibration

[aces-n-eights]

2006 Tahoe, LT, ~200,000 miles.

I get a high frequency vibration, like a buzz, right at 50 mph. I can feel it and hear it. It's like I'm driving on a road that has a slight corduroy surface. It's subtle, but I don't think these things get better with age and I'd like to track it down now.

It's at 50 mph... a bit higher or lower speed and it goes away.
I checked the tire pressure - all good.
I rotated the tires - no change.
I checked the driveshaft and it seems tight - no rotation slop or play laterally, up/down, left/right.

There is an oil leak on the front of the rear diff. Would failure of this seal cause a vibration?

What else should I check?

Thanks!

 

[Tonyrodz]

How's the trans? Rearend fluid good?

 

[aces-n-eights]

I replaced the trans fluid about 7,000 miles ago and it is at the proper level and smells and looks OK. No complaints with how the trans shifts.

I also replaced the rear diff lube at about the same time. Level is OK, the leak is not dripping the floor yet, but has made the front of the diff wet with oil.

 

[Tonyrodz]

Did you notice the vibration after servicing those? Was the vibration there before you serviced them?

 

[aces-n-eights]

No, this is a new vibration. It was not there when I serviced the trans and diff.

 

[M1Gunner]

How long and how intense is this vibration. Do you feel it all around or is it just in the pedal or just in the seat. Does the truck tend to slightly decrease in speed... anything else you notice? Any light come on? Abs tcs cel?

 

[aces-n-eights]

Thanks, Gunner, for your questions and help.

I think I have this figured out... I pulled into my garage last night, put it in park and heard a clunk. Went from drive to reverse a couple of times and heard a definite clunking sound. Had my wife shift it from drive to reverse as I watched underneath and it sure sounds like the clunk is in the rear diff.

So I think a bearing in the diff has worn out, causing the clunk and vibration, as well as causing the seal to fail which resulted in the oil leak.

Anyway, how hard is it to replace the front bearing in the rear diff? Should I rebuild the whole diff? Get a new/remaned diff? I am fairly handy with tools, and have a decent set of mechanics tools, but I'm thinking this may be a bit more complicated than I can take on.

Thoughts?

Thanks again for the help.

 

[M1Gunner]

I don't mean to insult your intelligence by any means but have you checked the u-joints on the prop shaft?

 

[M1Gunner]

Rebuilding your rear end is not a task for the DIY'er. Again, I don't know your capabilities or your tool box so I mean no disrespect.

One more question. If you grab the yoke (pinion companion flange) of your rear diff which of course is splined onto your pinion, can you move it up and down or side to side. Minor movement is acceptable but for the most part the play should be minimal.

 

[aces-n-eights]

I don't mean to insult your intelligence by any means but have you checked the u-joints on the prop shaft?

I just re-checked the u-joints and there does seem to be a small bit of play in the rear u-joint. But it does not seem to be enough play to make the clunking sound I heard. Installing a new u-joint is not too hard and probably should be done no matter what - if anything - else is wrong.

Rebuilding your rear end is not a task for the DIY'er. Again, I don't know your capabilities or your tool box so I mean no disrespect.

One more question. If you grab the yoke (pinion companion flange) of your rear diff which of course is splined onto your pinion, can you move it up and down or side to side. Minor movement is acceptable but for the most part the play should be minimal.

No disrespect taken at all! That is the conclusion I came to!

When I grab the yoke and try to move it up, down, side to side, there is virtually no play at all. If I try to rotate the yoke there is a bit of play. So there is play in the u-joint and the yoke (splined shaft?). In my original post I said there was no rotational play, but I had the parking brake on which I think took up some of the load.

Thanks again for your good comments...