a new problem occured Mack RB688S 1990 E7-400 camel back 46K multi-leaf shackle spring 18K dump truck the helper side tire is jerking up & down empty around 60 to 65 km(37 to 40 mph) and then get lot worst when loaded at around 70 km( 45 mph) . wheel seems to jump up & down tapping on the road . The steering is not jerking no feel of shimmy in the steering . The truck stays straight does not feel like it is going to bring me in the ditch nothing wobbles. what did I checked 1- tires are good (not broken not used abnormaly) 2- tires been balanced 3- tire from helper side went to driver side and vice versa ( same problem) 4- king pin been check and seems to have normal play 5- bearing been check seems good too 6- spoke wheel been checked seems good too 7- brake drum been checked seems good too 8- schock absorber been checked seems good too 9- tie rod end are sound 10- all spring leaf are ok no cracks not broken 11- all power steering rods and all others rods are sound 12- one thing that I found is that the shackle seem to be very close ( 1/8 )(see attached pics with the red arrow) to the rear holder helper side , on the oposite side (driver ) it is aroud 3/4 of an inch of space , also there is a play in the front pin of the front shackle . some people are telling it can be drive shaft related ( wich I checked and accordind to my knowledge all the plays seems to be within normal) . anyone had a similar problem ?