Whining at 40 mph
I've managed to get a ton of vibrations and noises sorted out with my jeep but theres just one last gremlin I haven't been able to figure out. A noise occurs starting at aroun 30 mph and grows louders until about 40 mph where it just about drives me nuts. After that the whine/howl cuts down a lot. The sound is just like the road noise produced by a tractor trailers tires.
There is very little vibration from this sound, it can only be felt as a sort of groan throught the steering wheel. The noise is completely independant of front driveshaft and of engine rpm's or load, meaning it doesn't matter if the front shaft is in or not and it does not change (at least not very much) from acceleration, deceleration, rpm, or what gear its in.
I did not notice this noise until a few months ago but 2 years prior I had replaced both the front hub bearings with Timken bearings and replaced both of the rear wheel bearings as well with Napa parts. Tires are DynoPro AT's and seem to be in pretty good shape but are slightly feathered with about 10k miles on them. Rotating them did not make a perceiveable difference.
One last little note, I had a Tom Woods driveshaft in for at least 5k miles that did not mate perfectly to the transfer case output yoke and thus caused the driveshaft to act out of round and out of balance. That problem is solved but could have let to others.
Jeep Info: 2001 XJ 4.0L NP231 Chrysler 8.25, 3.55 gears, 31" all terrains, Dana 30 LP, Pro Comp HD SYE.
What do you guys think could be causing this constant whine/howl at 40?
Please help, and thank you for taking the time to read this.
Live for those who have died for your freedom.