Well I bit the bullet and got a newer set of wheels to drive around. 2016 f-150, 140,000 miles on it. Got lucky and found a xl, which got me the cloth seats, no center console, and rubber floors.
And of course, its not perfect.
5.0 six speed auto, 4x4 with rear axle locker. No prior history on the truck.
Randomly driving down the road, I get a "rumble strip" vibration of about 2-3 seconds, then it goes away. Mostly happens at highway speed, doesn't seem to be caused by pavement imperfections, but does seem to happen mildy less often on a stretch of new asphalt near the house (but I'm not as fast there). Nothing seems loose in suspension or steering. Shifts fine, and doesn't do it when hitting deep dips or holes in the road.
I made a run to western kansas last week with it, and it was very frequent running 70-80 out in the plains. Maybe two times in every 5 minutes. Closer to home and less speed- maybe 5 times in a hour.
I thought originally bad struts/ rear shocks, but it handles fine. I've been reading and fixes are all over the map, but what seems likely is either torque convertor or rear axle.
My plan is drop pan on the transmission, full flush and I've ordered some "lube guard instant shudder fix". Also plan a rear axle drain and replace fluid and do a debris check.
Any other ideas from you guys that work on these every day?
Other than the "rumble strip" effect, seems like a good truck.