rear end trouble

[xpl951]

I have a hmmm......hmmmm........hmmm and shake in my rear axle at 60 then nothing till 75-80 and its just a shake no hmm noise.
97 4.0 ohc 114k i changed the diff oil new tires only 4000mi new trans 4000 mi rear ujoint at 100k

any ideas?

 

[my pos mounty]

That sounds like a balance issue, probably in your driveshaft or tires

 

[xpl951]

tires are new michelins and rean like slik till exactly 55 hmmm noise then silk again.
had them rebalance them and im where i was with my rt/s pos tires.
in the 4k on the tires i have a rebuilt front drive cv and new trans and tq converter.
so im unsure what the prob is.