2000 F250 4x4. Sterling 10.5 rear axle.
There is a knocking noise coming from the rear axle only when coasting with no load on the drive train, starting at about 35 mph down to about 5 mph. The knocking goes away when I manually lock the torque converter. It also goes away when I "feather" the accelerator lightly enough to raise the engine rpm, but not enough to maintain speed.
It is more consistent with the speed of the tires than the drive shaft. The noise can only be heard with the radio off and windows up . . . in other words, it has to be quiet in the cab. As a result, I don't know how long it has been doing this. I first noticed it, however, after I swapped the gears from 3.73 to 4.30 ratio. After changing the gears, I was overly focused on any noise from the axle to ensure that I didn't do anything wrong.
When doing the gears, I noticed that the limited slip differential was beyond shot. I didn't have a replacement, and it looked good enough to last a month or so until I could find a good, used (affordable) differential. I figured the differential was the source of the noise, and dismissed it.
Fast forward about 500 miles/1 month. I laid my hands on a good, used 3-pinion LS differential out of a newer truck for a great price. I disassembled it upon delivery to ensure it was in good shape and replace clutches if necessary. It checked out with nothing more than a thorough cleaning, and installed it into the axle. I checked the pinion gear pre-load and spun it by hand, it was still good.
The knocking noise persists! I checked out the wheel bearings, which are fine. I threw the rear end up on stands and had the wife run the go-pedal to duplicate the conditions. It is most certainly coming from the center section. I can hear it very clearly under the truck next to the axle, and, placing my hand on the center section, I can feel it. Turning the tires by hand, I can hear a very quiet knock about once for every turn of the tires. I just can't figure it out. I can't afford to keep opening the rear cover, either, at $60 a pop for that expensive 75W-140.
There is a knocking noise coming from the rear axle only when coasting with no load on the drive train, starting at about 35 mph down to about 5 mph. The knocking goes away when I manually lock the torque converter. It also goes away when I "feather" the accelerator lightly enough to raise the engine rpm, but not enough to maintain speed.
It is more consistent with the speed of the tires than the drive shaft. The noise can only be heard with the radio off and windows up . . . in other words, it has to be quiet in the cab. As a result, I don't know how long it has been doing this. I first noticed it, however, after I swapped the gears from 3.73 to 4.30 ratio. After changing the gears, I was overly focused on any noise from the axle to ensure that I didn't do anything wrong.
When doing the gears, I noticed that the limited slip differential was beyond shot. I didn't have a replacement, and it looked good enough to last a month or so until I could find a good, used (affordable) differential. I figured the differential was the source of the noise, and dismissed it.
Fast forward about 500 miles/1 month. I laid my hands on a good, used 3-pinion LS differential out of a newer truck for a great price. I disassembled it upon delivery to ensure it was in good shape and replace clutches if necessary. It checked out with nothing more than a thorough cleaning, and installed it into the axle. I checked the pinion gear pre-load and spun it by hand, it was still good.
The knocking noise persists! I checked out the wheel bearings, which are fine. I threw the rear end up on stands and had the wife run the go-pedal to duplicate the conditions. It is most certainly coming from the center section. I can hear it very clearly under the truck next to the axle, and, placing my hand on the center section, I can feel it. Turning the tires by hand, I can hear a very quiet knock about once for every turn of the tires. I just can't figure it out. I can't afford to keep opening the rear cover, either, at $60 a pop for that expensive 75W-140.
