Our 1998 Disco has a slight vibration between 45 and 50 mph. Can't find any play in the grease-able u joints. Any idea's what this may be. Tires have been balanced. Maybe it needs new u joints. We bought it it used and it already had the grease-able joints.

 

I would try greasing the ujoints up real good and see if that helps. Next i would rotate your tires... its hard to tell what would be causing a vibration at that speed it could be any number of things

 

Did you check the u-joints for play with the truck off the ground? (jackstands)

Twist them (rotational play) and shake them (lateral play)

I've pulled bad ones that had almost no play but were binding from lack of grease.

luck,greg

 

I even took the front driver shaft off to check for play in the u-joints. Maybe I will just replace them as we don't know how long they have been on. We are going 4x4ing in Moab next month and would hate to break down there a thousand miles from home.

 

While you have the front drive shaft off lock your diff and go drive it. Just be easy on the take-offs and you will be fine. If it still vibrates at the same speed I would just grease the UJ's, put the shaft back on and continue the search for the culprit. Easiest way to determine if it is the front drive shaft. Good luck!

 

how old are your tires? when did you last have an alignment?

 

A binding u-joint will have no play, but will cause vibration.
If you get grease from around all 4 seals when you lube them, odds are pretty good they aren't binding.
If you can't get grease from around all 4 seals you need to replace them even if they aren't binding.

Tires would be the first thing I check. When were the tires balanced? Did the vibration come on suddenly? If so, maybe you threw a weight.
Rotate your tires to see if you notice any difference.

 

Have had tires balanced recently. Grease doesn't come out of all 4 seals, so I will be changing u-joints. Thanks everyone for your imput.