rockfoot

I am not sure if I am hearing something that is not supposed to be there or something that is supposed to be there. I want to check with other D-250 owners out there. When I first bought this truck, it had about 210,000 miles on it and it was very well taken care of. All the maintenance figures and receipts, that kinda stuff. The previous owner didn't spare a dime on maintenance. Very well kept. When I first drove it home from Myrtle Beach, I heard a vibration in the driveshaft in forth gear and if I accelerated firmly, say it was lugging just a little, the vibration would get very loud. A Ringing, hollow, driveshaft kind of sound. I assumed that the U-Joints and center bearing were probably due and that is where the noise was coming from. I bought the parts and they got hauled around in the tray behind the seats for a couple of years, the noise not really getting any worse. I finally changed them out but really didn't like the looks of the u-joints bosses when I installed them. The noise was the same after the installation. I then figured that I had let the parts flop around behind the seats too long and that they, too, were bad (Brinnell effect) and I would get some fresh ones later on.
I just last week rebuilt the Getrag 360; very carefully installed new, fresh u-joints, and replaced the throwout bearing. Replaced the rear axle bearings and seals, opened up the differential, wiped it out real good, flushed it, replaced the gear oil and cleaned out the vent. In the transmission, the input bearing and shaft had to be replaced. The bearing was gaulded and had been very hot and the shaft was discolored. All of the rest of the bearings looked good as did the rear seal. The front seal was non-existant. The propeller shaft nut was loose. The 3-4 gear shift fork was worn out, with no material (aluminum) being transferred to the sync slider. This was the original reason for going into the transmission to start with. Seems like somebody was resting they're hand on the shifter while in forth..... The point I am trying to make is that I did a lot of stuff that rally made a lot of the noises go away. The transmission shifts perfectly and has zero whine in any gear. I set the backlash on the gears at +.006. With the back sliding window opened, I hear no noise at all from the drive train..... except in forth gear, still. Is this a normal noise for the Getrag? With the rear sliding window closed, I barely can hear it.... any input would be appreciated before I spend another bunch of money trying to get rid of a noise that might supposed to be there...

wannadiesel

Getrags typically rattle at low RPM in 4th. It's the unloaded countergear slapping back and forth from the power pulses from the engine. If it only does it in 4th at low RPM you are fine.