Turned out to be a U-joint, droped the drive shaft and the rear joint was toasted. Replaced with a neapco brand with zerk fitting. I was able to use a pitman arm puller with a socket on the end between the flange and cap to press out the joint. Thanks for all your help guys/gals

 

i was gonna say, even if you can't feel play in them they can still be bad. i had a similar issue a while ago and i couldn't feel play in the ujoints so i assumed they weren't the culprit. as soon as i dropped the driveshaft, that ujoint was wobbling like nobody's business.

 

Went back and read my first comment... which was u-joints. On the play-thing... I suspect you could have "unloaded" the joint and felt the play... but I could be wrong. The thing that was different that you had was that you didn't get the symptom at low speed.

Otoh, I have a sharp down hill dirt road, about 3/4 miles, which tends to show problems more easily as the joints are worked... so maybe my experience is different.

Could also be that I tolerated the symptoms long enough to more easily detect the play.

Anyway... congrats on finding the problem.. I know they can be annoying.