Originally Posted by
Slowpoke Slim
I've had the same problem here a couple of times with my '12 F250. I think it's also cold related. I haven't really worried about it, as my theory is it's due to the cold temperature of the fluids in the driveline. Most likely it's the temp of the fluid in the front end. The "clunk" comes from the front gears coming up to the same speed as the Tcase and rear end as it all meshes together. I also notice it happening more if I'm turning at the same time the 4wd is engaging.
There is no question that is cold related and it is a timing issue with the hubs. When the hubs are locked manually there is no noise ever, it is only in auto mode and IMO and the service managers it is not right. I have driven in a number of these trucks and none of them made the same type of noises so I guess ours are special edition units. Mine is a job 1 2011. I guess we will see what happens after a TCase rebuild next week for this issue. FWIW, they went through all the vacuum timing etc and everything is right by the book on mine for timing and vacuum levels and no vacuum leaks at all.