My F-250 has recently developed a clunk in 4wd...

The other day I was simply driving around w/ the hubs locked but out of 4wd. I noticed an unusual 4wd related (slight) vibration. I didn't think much of it but as I was going about 20-25 I felt/heard a clunk and a slight jolt through the truck, and the vibration went away. I didn't think much of it at the time, but heard it about 2-3 times over a few days...same deal...vibration...clunk...then no vibration.

We've had some snow lately, and the clunk has stayed the same but happens way more often. It seems to clunk every mile or so now, atleast. It hasn't seemed to matter whether i'm actually in 4wd or not, just as long as the hubs are engaged. However, on the way to and from work today I was using 4wd for awhile and noticed it did seem to clunk a little more often when in 4wd vs out...but it's the same clunk/jerk. I took a peak at the u-joints last week and they weren't falling apart, but I havn't actually inspected anything yet. When the snow clears I was thinking about removing the driveshaft and testing it w/ the hubs locked/unlocked and w/ the lever in 4wd/out of 4wd to see if I can narrow it down to either the front end or TC. Any preliminary thoughts before I dive in for inspection?

 

I would go and give all 5 u-joints in the front drivetrain (3 on the axle and the 2 on the driveshaft) a good once over, give them a good shake and get right in there with a light, if they move in the cups then they are toast and most likely your problem, my guess is that it is the joints in the knuckles.

 

joints is a good place to start. another place to look would be your hubs...sounds like they could be slipping in and out of being locked/unlocked

i dunno, sounds like one of those things that you just don't know until you tear into it.

-cutts-

 

yeah like cutts said, but start with the stupid easy things (the things that are easy to find, might not be easy to fix though) first as those usually what happen and it always sucks to find out you did all the work and spent all that money when it was a 10 minute, 10 dollar part (at least we all hope its something like that.

 

I'd check the slip yoke & middle ujoint on the passenger side axle. i've had those slip yokes freeze solid. plus, since the passenger side is longer & weirder, i'd start there first.

does the 4wd work? if so, i'd probably say in is in a ujoint and not a hub..

or if you want to find out what is bad real quick and painful, shift into 4lo and do some donuts in a parking lot (preferably a paved parking lot) (just kidding)

 

The 4wd does work....I'll take a closer look when the snow is cleared.

On the way to work today I noticed that it doesn't clunk much when out of 4wd, but when you're in 4wd or have recently gotten out of 4wd...it clunks pretty bad now (hubs still locked the whole time).

 

Either you're accelerating towards disaster, or your mind is getting ahead of yourself.

I like Bremen's idea. That'll solve the problem REAL fast. Just wait till your dad is with you and the 393 is in the other truck so you have a tow vehicle.

 

I've come to the conclusion that it doesn't clunk when the 4wd is not engaged/hubs locked...but it'll clunk right away when you pull the shifter into 4wd. I was driving in about 6" of snow going slow and it didn't clunk, so speed has something to do with it as well. I'm hoping u-joint...but I still havn't looked yet, too cold/snowy out for now.