Hi, well i have a 78' R686st mechanic's special truck that i bought and put a 14' dump bed on and done alot of fixin up. anyway it makes this banging noise and jerks. it don't do it all the time, i can make it start doing it with heavy acceleration, etc. it has tandem 38k axles wit 4.50 gears it says. i have put all new caps on trk. I have replaced and checked almost everything i can think of, have changed trans, replaced wedges and cams, spider gears,axle gears, bull gears,axles,etc I have counted all teeth on one gear carrier, but forgot to count on frnt carrier before i stuck in back down in housing. What are the odds of having different ratio's? What is acceptable size/wear difference between rear tires?
first thing that i would check is the tire height between #2 and 3 axles. mack diffs have very little tolerance for any difference in height. the difference is taken up in the front diff power divider which binds up and then releases causing a banging and and jerking condition. have seen this dozens of times and is almost always cured by having matching tires installed.
R686St Banging Noise And Jerking
in Driveline and Suspension
Posted
first thing that i would check is the tire height between #2 and 3 axles. mack diffs have very little tolerance for any difference in height. the difference is taken up in the front diff power divider which binds up and then releases causing a banging and and jerking condition. have seen this dozens of times and is almost always cured by having matching tires installed.
mike