I have a M35A2 that has been modified with one axle removed. I have been running it this way for a few years with no problem. Now there is a strange noise. There is a pop sound with a simultaneous jerk in the drive train. It happened about every 8 seconds at highway speed and under load. I have the air shift transfer case and lock out hubs on the front. I can completely disengage the front driveline and the popping is still there.
Just before the noise started, I swapped the rear axle guts with Ouverson 2 inch axles and locker. While I was there, I re shimmed the gear lash in the differential and measured everything. I even put a girdle on the bearing caps. I also replaced the injection pump head because it was leaking on the #3 line.
Since I just replaced the rear axle shafts and locker, I took the truck up a very steep hill in 2wd to see if both wheels will pull to verify the locker is working. Both tires spin and remain locked.
I started out by replacing the drive shaft u-joints. They were old and had a tiny bit of play. I’ve even swapped out the entire transmission to transfer case shaft drive shaft twice with no luck. I put the truck up on blocks and drove the wheels, and I could not duplicate the noise with no load.
Eventually I checked the oil in the transfer case and found very thin pieces of metal. I pulled the transfer case and found the metal came from the input shaft dust cover from a bearing. The dust cover came loose and got chewed up. There is no damage to the bearing s or gears. The metal was caught by the magnet. I went ahead and swapped out the ball bearings in the transfer case. This time I removed the dust covers to prevent this from happening again. The roller bearings on the other shafts were in perfect shape. I reinstalled the transfer case and the popping was still there.
Next I pulled the rear hubs to check the bearings and brakes. They were in perfect shape. Now in attempt to diagnose where the noise is coming from, I removed one of the rear axle shafts. The noise was still there. Without the axle shaft, there is no possible way that it was the rear locker. I then removed the rear drive shaft and drove the truck using the front axle. Popping was still there. Now I know it can’t possibly be the drive shaft since it was completely removed and the noise is still there. I put the axle shaft and drive shaft back in.
At this point, I set out on a 600 mile round trip. Truck popped the whole way (about every 8 seconds). On up hills the popping happened more frequently and was louder. On down hills, the popping was non-existent. Right before I got to my designation, the clutch was slipping. I pulled over and stopped and found oil pouring out of the hole in the bottom of the bell housing. I immediate assumed it was the rear main seal even though I replaced it a year earlier. I pulled the transmission and replaced the seal and clutch. The clutch was in very good condition though and the seal also looked like there was no damage. I got it back on the road and the popping was still there. I drove it back 300 miles and noticed that oil was again leaking from the bell housing hole.
It turned that the transmission oil was leaking and not the engine oil. So I took the top cover off the transmission and found that the 5[SUP]th[/SUP] gear on the counter shaft was missing teeth. There were about 2 spots where the 2 teeth in a row were missing and there were 2 other spots where 1 tooth was missing (total of 6 teeth). So here is where I thought I found the smoking gun. I replaced the bad 5[SUP]th[/SUP] gear and inspected all other gears and bearings. About a year and a half earlier, I rebuilt the transmission because 5[SUP]th[/SUP] was slipping. I had already replaced both the 2-3 sincro and 4-5 sincro along with 5[SUP]th[/SUP] gear on the main shaft. While I was in there I inspected these parts and they were in great shape. All the transmission bearings are in perfect shape. I inspected the pilot bearing and on the flywheel and found that it was worn out. I was thinking that the loose pilot bearing allowed enough play allow 5[SUP]th[/SUP] gear to get overstressed, and allowed misalignment to allow oil to leak out. I put the transmission back together and the popping noise along with the jerk is still there.
I made another trip and the popping is happening about every 4 to 10 seconds. Under load it happens more aggressively. Costing down a hill, it doesn’t happen at all. There was no sign of leaks until I went up a steep hill. The popping was very aggressive and after the hill, I pulled over and noticed a small amount of transmission oil dripping out of the bell housing.
I went ahead and pulled the front hubs to inspect the bearings and brakes. They were in perfect shape. The lockout hubs are in great shape and functioning properly.
Now I’m completely dumfounded by the popping.
(on the upside if it is your rear end which I kinda doubt you have a spare!) I only say i doubt its your rear end because in my 9 inch rear end it sounded like a grenade going off every time I took off a tooth, I would imagine it would be really really really loud on a rear end the size of the deuces? It doesnt sound like yours is that loud?
