how big job to change axle seal on front of a 3500 4x4 2008 thanks

 

It is not difficult, but requires plenty of room to work and care in handling the axle to avoid damaging the new seal.

Either side requires you pull the wheel, hub, steering ball joints, and then remove the axle to pop the old seal and insert the new one.

Sit down with the repair manual and go through the section on axle and seal replacement.