Mostly the truck is very quiet, and i like that.
But at around 1500RPM on the highway, there is sort of a exhaust buzz or humm that goes away if i let off of the accelerator.
Possibly a leaking exhaust line or worn out muffler?
I have no CAT codes. It is a 04 SLT 3.7 with 134k miles.
Any thoughts on this?

 

 

Im thinking U joint, rear wheel bearing, differential something to look into have you checked the diff oil could even be a front wheel bearing or hub?

 

agreed, speed dependant sounds more mechanical than exhaust. Unless it does it in neutral/park as well? If so, I'm thinking harmonic exhaust leak at the manifold flange.

 

humm, thank you. will try it in park.

 

OK had a mechanic check it out.
He said that what i was HEARING was actually the exhaust BUT what i was FEELING was actually a wheel bearing what was showing its age.
The symptoms of different sources were apparently overlapping.
Go figure.
He said it was nothing to worry about, but he would not do an alignment until the bearing was replaced.

 

If you have a bearing that's vibrating enough that you can feel it, you REALLY need to get that changed out.