I have a 2001 dually F-350 super duty 4x4. This truck is equiped with manual lockouts. When ever the lockouts are engaged, the front diff makes a knocking or thumping sound when turning to the right or left. It usually starts at about 2/3rd's turning radius. This is with the transfer case in the 2wd position. If I unlock the hubs the sound goes away. I've had it looked at by the dealership and they say it's fine. Any ideas?

 

Do you have Limited Slip in the front? That would be my only guess, that the LS is kicking in. Other than that, someone else would have to chime in since I don't know a whole lot on 4x4s.

Gary

 

it sounds like your u-joints are bad i dont think these truck have limited slips in the front.

 

Dale,

This is a normal occurrance when you turn tightly in either direction with the hubs locked because now the axle shafts are connected to the wheels and so the ujoints at the nuckles are turning along with the axle shafts and they bind up slightly when you turn sharply in either direction. Just to be safe you can grab the ujoints and see if there is any excess play in them.

Also welcome to FTE great people and info around here.

BTW when start a new post for a title pick a description that describes your problem and this will draw people with the answer to your thread quicker.

 

Both my 99 and 04 F-350's made the same noise with the hubs locked,,my 06 does not make the noise, and I have had the hubs locked almost 1000, miles now,,this new truck is a thing of beauty to drive !

 

Dale, I have an '01 F350 4X DRW as well. Have the auto lock front hubs and have noticed the same. Only seems to happen if I have it in 4X with hubs locked and go from dirt to pavement. Probably what blackhat20 says - axle shafts are connected.

 

Thanks for everyones replies. Great site!