Hi, I have a 2013 Express 2wd with the 6.0L gas with 150,000 miles on it. It has a vibration that feels like driving over rumble strips intermittently ranging from 40mph to 65mph. It seems to do it more when it has been sitting for a little while. So far I have replaced both front wheel bearings thinking one was possibly getting worn, checked the drive line and all is tight besides a little bit of play in the slip joint, inspected the differential after changed the gear oil, transmission fluid is in good condition, ball joints and tie rods have a little wear but not bad, checked for codes and it has none, rotated the tires and that made no difference, motor mounts seem to be in good condition. Not really sure what to check next and I don't want to throw parts at it, any help would be much appreciated.

 

How about the idler arm bracket? Nobody (except me) ever greases them. I got the extension hose to make greasing it easier. https://www.rockauto.com/en/moreinfo...08860&pt=13418

 

Which idler arm bracket do you mean? If you mean for the steering this has a rack and pinion for the steering