SERVICE MANUAL TROUBLE SHOOTING Serious  trouble  in  a  rear  axle  can  be  prevented  if sufficient   attention   is   given   to   the   various   causes   of trouble and the proper remedy is applied.  The following list gives most of the common kinds of axle trouble and suggests a possible cause to be corrected. Constant Noise 1. Lubricant not to specified level. 2. Incorrect kind and weight of lubricant. 3. Wheel bearings out of adjustment or defective. 4. Drive  gear  and  pinion  not  in  adjustment  for  correct tooth contact. 5. Teeth of drive gear and pinion chipped or worn. 6. Too  much  or  too  little  pinion  to   gear   backlash   or overlap of wear pattern. 7. Loose or worn pinion bearings. 8. Loose or worn side bearings. Intermittent Noise 1. Drive gear does not run true. (a) Uneven pressure on drive gear rivets. (b) Warped drive gear. 2. Loose or broken differential bearings in either axle or in inter-axle differential. Noisy On Turns Only 1. Differential pinion gears tight on differential spider. 2. Side gears tight in differential case. 3. Differential pinion or side gears defective. 4. Thrust washers worn or damaged. 5. Excessive backlash between side gears and pinions. It should be noted that noises from other units of the truck such as propeller shafts, universal joints, tires and even  transmissions  are  often  incorrectly  diagnosed  as rear     axle     noise.          This     possibility     should     not     be disregarded when trouble shooting. Lubricant Leaks 1. Loss through axle shafts. (a) Lubricant above specified level. (b) Incorrect kind and weight of lubricant. (c) Restricted axle housing breather valve. (d) Worn or incorrectly installed axle shaft oil seal. 2. Loss at pinion shaft. (a) Lubricant above specified level. (b) Incorrect kind and weight of lubricant. (c) Restricted axle housing breather valve. (d) Pinion oil seal worn or incorrectly installed. (e) Lubricant return passage in diff  carrier  housing restricted. (f) Universal    joints    companion    flange    loose    on pinion shaft. 3. Loss at axle housing cover. (a) Insufficient or defective seam weld. (b) Cracked seam weld. Rear Wheels Do Not Drive (Propeller Shaft Rotating) 1. Broken axle shaft. (a) Loose wheel bearings. (b) Axle shaft too short. (c) Loose flange studs or nuts. (d) Bent housing. 2. Drive gear teeth stripped. 3. Side  gear  or  differential  pinion  broken  in  either  axle or in inter-axle differential. 4. Differential  spider  broken  in  either  axle  or  in  inter- axle differential. CTS-4044 PRINTED IN UNITED STATES OF AMERICA Page 29