I have a 98 2500 Quad Cab Cummins 4x4 with about 220K miles. Generally runs great. Front end is tight. Fresh ball joints and tie rod ends when needed. Bilstein shocks. No rattles, clunks, shimmies or wobbles. However....

Starting just recently, it makes a groaning/humming noise when I hit a bump over 20 mph and often will stop when I hit another bump. I've had wheel and axle bearings go bad and the noise is usually speed related and has nothing to do with hitting a bump. When I get the noise, I don't get any vibration or other symptoms. Just the hum/groan. It does not appear to change pitch with speed. Noise goes away when I hit a bump or slow below 20 mph.

I've confirmed that it is not engine or transmission related. When I get the noise and shift to neutral, i can rev the engine and the humming noise does not change.

The steering and ball joints are all tight.

Any idea what could be causing this noise?

Suggestions/experiences greatly appreciated.

Boatman.

 

Just wanted to report back to the folks here on my weird humming problem. Everyone I talked to was convinced the front hub bearings were going. That' wasn't it.

Turned out to be dragging front brake calipers. They were both dragging badly and it seems that they can hum when they drag. I've heard dragging calipers squeal and shriek before but never hum. Live and learn. Thank goodness I caught it before the rotors got chewed up or warped.

A set of rebuilt calipers and new pads and no more hum. Better stopping too since the pads don't drag anymore and heat up.

FYI - During the job, I noticed that all three brake lines leading from the ABS block to the junction block were very rusted. Decided to replace all three and two disintegrated on removal. In looking at it it's a bad place to put a junction block with all the spray from the driver front wheel. Dodge gives each of the three brake lines a different thread pitch and size so you don't mix up what goes where. Also means they are really dealer parts. Cost me $108 for all three. Peace of mind, tough.

Boatman.