01 f350 7.3 zf6, manual shift case. 589,xxx kms on it.
I tow almost every weekend. Not too heavy, probably 6000ish lbs, plus a load of bikes on the back. Truck scales just under 9000lbs typically. Big bumper, winch, heavy deck, a lot of tools, etc.
A month or so ago it started growling badly while towing home. I checked all U joints, which felt happy, spun the front wheels...all I found was some ****ed ball joints. Did a tire rotation. No changes.
Trans juice was pretty sparkly. I dropped it, had it rebuilt. Rebuilder has an excellent reputation. It no longer growls. He did bearings, syncros, two hub and sliders, input shaft and one fork.
I did a sintered bronze pilot bushing instead of a stock one.
However.
There is still an oscillating type noise from about 55-65 km/hr unloaded at neutral throttle. Zero pedal, no noise. Hard on it, no noise.
Towing, it's there from 50ish km/hr up to around 90km.
It seems to both my wife and I (from her spot in the passenger's seat), to be coming from right by my feet while driving.
I've done the rear end fluid, it was happy. I'm waiting for another u joint and I'll do the center one on the rear axle this week. That will be the last one.
Tcase fluid looked fine.
Manual case, manual hubs, so nothing in the front end is engaged or under load. I marked the front shaft to make sure it wasn't spinning, went for a drive, confirmed. Noise is the same in 4H with hubs unlocked, as in 2wd.
Any ideas?