Not sure what is going on but wanted to hit this forum to see if anyone out there could help me out. i have a 1999 jeep cherokee and for some reason at 50-60MPH i am getting this rhythmic vibration coming from the floor. is sounds like i'm running over the grated concrete they put on the side of the highway to wake you up when you're off the road. not sure why it's doing it. any ideas on what to check? it feels like it's coming from the floor underneath my feet.

 

Are all your ujoints in good shape? One of mine on the drive shaft was going bad causing some nasty vibrations.

Crawl under there and shake the driveshafts. You should have no play at the u-joints. Check the front axle-shaft ujoints for play as well. Cheap and easy to fix in the driveway (or street, if you're like me and don't have a driveway or garage)

 

A bad front driveshaft is a common source of vibration/grinding.
Try taking it off and driving without it and see if that improves
things. Examine the driveshaft for bad u-joints, a worn centering
yoke in the double cardan, or a sloppy, worn slip yoke.

While you are at it, check the front pinion yoke for play,
lateral and in/out to see if there is a bad pinion bearing.
Make sure the pinion nut is tight.

 

mine did the same and I later found that the front driveshaft was out of balance.

 

I would rotate the tires first...just to eliminate tires. While doing that, look for uneven wear or cupping on the tires. Be sure to look all the way around the whole tire....Would be beneficial to have them balanced again before remounting if possible. If the hum is exactly the same, then it could be bearings, u-joints or a combination of both.

 

i have a similar "highway strip noise" when I'm decelerating only, around the same speeds. i narrowed it down to my rear pinion bearing. there is no play at the yoke, but when removing the rear driveshaft the noise goes away completely.

maybe try removing the front driveshaft, see if it still does it. if not, remove the rear and try again.

 

Sounds like a ujoint. Basic stuff. Easy fix.

 

Ever check your motor mounts, trans mount, bolts holding trans mount to housing?