The last couple of weeks a new clunk has appeared on my F350, 6.2 CC LB FX4. If I've been parked for a while, when I drive off, within the first 30 yards or so there's a clunk. Seems worse when I've turned sharply out of a parking spot. Sounds like the rear diff or drivetrain... I have a locking rear diff. Is this engaged or disengaged while "at rest"? Could it be that its slow to unlock when I start? Thanks for any help and suggestions.

 

It should be disengaged when OFF, and engaged when ON. If you turned off the vehicle while it's ON, I believe it would stay ON, and still be ON at the next startup.


See if it still happens when you turn Trac & Stab control off. press once for Trac off, hold 5 seconds for Stab off.


If it wasn't there before, and now it's constant, and it won't go away, then it's prob not a normal function..


What rear gear do you have btw?

 

Thanks Wolf! I haven't had the diff locked except to verify that it worked when I bought the truck last summer. So its not a question of having it set ON when I parked. However, I recall something here about vacuum lines used to engage or disengage diff locks, and wondered whether vacuum was required to keep the diff unlocked. If so, then a slow vacuum leak would explain my symptoms, in that the clunk only happens after the truck has been parked for a while, never happens during regular driving. I tried switching off Advancetrac (good idea! :-). No change, still clunks. I believe the diff is 3.73.

 

Try climbing under the vehicle and see if u can twist your drive shaft or there's play in between the drive line and rear end. Could be slack in between the ring and pinion.

 

could be a sticking disk brake caliper slide pin...on the rear brakes. 1 side or both.

 

Do a forum search on Super Duty clunk.

 

Not exactly the same problem but might be a contribyting factor

Slip joint regreasing

 

Good Point... easy check.

 

I had the same kind of clunking noise as well, what I found was that I had a bad rear swaybar end link. The one on the passenger side was bad and could lift it up and down by hand. I replaced them and the clunk went away. JFFT

 

Many thanks for the responses guys, I appreciate your input! Seems I have an "action list" for the weekend... (if it doesn't rain! :-).

 

Also check your shocks. They'll rattle more than just at start up though. I had a loose rear shock on my 2011 F350 last year. Took me about five months to figure it out. Thought it was something rolling around in the back. Finally decided to check the shocks; they were loose enough to move with my hand.

 

Hi Scooter22,

Have you had a chance to visit your dealer since the clunking started? Please let me know, along with your kilometers.

Meagan

 

Nope, haven't been to the dealer, and it won't go there unless I can't figure this out myself... :-)

Odometer is around 180K

 

Thanks! If you're unable to tackle this yourself, your dealer's a great next step.

Meagan