We got a little snow last wk so for the heck of it I locked my manual hubs. Didn't use the 4wd, just locked the hubs. I figured it was a good time to run the axles for a while anyway. I ran the trk with the hubs locked for some time, several days, several trips here and there maybe a total of 50-100 miles. No problems, not even any difference in drivetrain sound from the axles turning, etc. I had to make a sharp left turn off of a main highway onto a side road, just about turning to the steering stops when I got a thump, thump, thump or maybe it was a bump, bump, bump, I don't know but I could feel it in the left wheel and hear it. Truck has 2400 miles on it now and is treated with TLC. Can anyone tell me what this may have been. Is this a sign of something wrong that I need to address? Thanks guys.

 

Have you ever owned a 4X4 before? Not trying to be insulting at all so don't take it that way, but 4X4's clunk and bump and are even a little squirley! When the wheels are locked in and you make a turn the turn on the front is shorter than the turn in the back so you will get a bump or a thunk, or just plain old 4X4 noise it happens mostly on hard pavement when the wheels can't slip. Enjoy it and by all means don't baby it, these things are built Ford tuff!!!!

 

Check your axle shaft joints for play, that low of mileage, you shouldn't have any.

 

What you experienced is completely normal and nothing to be concerned about.I'll try to explain.
When you turn your wheels "sharp" and the hubs are locked your U-joints are operating at an extreme angle.What your are hearing is the u-joints indexing.(I hate to use this phrase,"binding",nothing severe because they are turning so slow that there aren't any harmful vibration harmonics at work.)When you are driving at normal road speeds it won't happen because you don't turn the wheels that sharp when cruising down the road around bends and negotiating normal street corners.
What you are experiencing is exactly why front wheel drive cars use constant velocity joints.They can operate at more severe angles with out the associated "binding" effect.Of course they're using their front steering driveline constantly.
The same thing happens with u-joints when large lift kits are installed and the driveshafts aren't modified accordingly.The angle gets too steep and the u-joints vibrate.Of course they are spinning fast on a drive shaft at extreme angles and in turn won't last very long.

You could always see for yourself by observing someone very slowly moving your truck while turning it at near or full lock with the hubs locked and the transfer case in 2wd..If you were to look at the u-joints you would be able to see what kind of angle they're operating at in this situation.

Hope this helps explain it.

 

Thanks for the replies guys. Makes sense, I feel better now.

 

BTW,
it's not anything that either of mine doesn't do.