Drivetrain noise

[aaronb]

My truck has picked up a drivetrain noise. It sounds like a scratching sound. It doesn’t do it continuously. It makes the noise, goes away, and makes the noise again while coasting. I can also hear it when I let off the fuel to shift gears. If i push in the clutch or take the truck out of gear the noise goes away. I’ve tried speeding the engine up while stationary and while coasting out of gear and it doesn’t make the noise. I checked the ride height because I put new tires on last week and it’s in spec. My truck is a 2013 Peterbilt 389 with an ISX, 18 speed, and 3.55 rear ends for reference. It has 720,000 miles on it. The engine was rebuilt at 480,000. The power divider about 100,000 miles ago. The clutch was replaced at 360,000 miles. As far as I know the transmission hasn’t had any work. If you have any ideas I’d appreciate it. Thanks.

[hhow55]

Most likely cause is your carrier bearing is bad, or your inner axle has excessive slack.
While your under the truck, check all the u joints.

[aaronb]

I forgot to mention I changed the carrier bearing and replaced the u joint behind the transmission 30,000 miles ago. I checked the u joints and they all feel tight. The shaft going in the front of the front differential I can pick up and down just a little bit. Maybe a 1/16 of an inch?

[TruckerMatt]

Weird noises, Rattles, vibrations can be so annoying. Older the truck the more it could be a combination of many things.

Start with the easiest first then work your way up. I chased a vibration and noise for 2 years. It seemed like it was a bunch of collective group of problems. I Greased and shaked the Driveline often, tapped EVERYTHING with a small ballpeen hammer. If something is loose you will hear it, I found a VERY loose steer axle u bolt and a drive axle torque arm loose.

Measure and check ride height and recheck it and move it to different heights to see if a change occurs. Mine runs smoother slightly lower (1/2") than specs. Adjust your clutch. Wheel balance. If it takes alot of weights on steer axle replace the wheels. Check your rubber hood rests and guides, one of mine was missing.

LISTEN TO YOU TRUCK JUST IDYLING...do you here funny rattles or noises at idyl? They can be worse at 65 going down the road. A very loose exhaust stack will feel like a bad tire or shimmy. If applicable Check your PTO mounts, bracing, hydraulic hoses etc. check fuel tank mounts too!

I grease my driveline once a week ... and tap everthing with the small hammer.

If you have one on your truck check the Vibration Damper spring between the rear of the tranny and running up to the upper cross member, it should have tension on the spring. Carrier bearing was replaced, ensure carrier bearing is perpenducular and not "canted", driveline removed inspected and the balance checked, I even did a inter axle "jackshaft" replacement", I reversed my driveline around so male points rearward "driving into the female", new shocks, new torque rods & tortion rod bushings, then did a complete wheel alignment and balance. Wheel bearings inspected and retorqued, Engine mounts checked. Driveline angles checked. Then new steer axle King Pins.

Everthing I did made a gradual improvement.

[TruckerMatt]

(05-04-2018 )aaronb Wrote:  I forgot to mention I changed the carrier bearing and replaced the u joint behind the transmission 30,000 miles ago. I checked the u joints and they all feel tight. The shaft going in the front of the front differential I can pick up and down just a little bit. Maybe a 1/16 of an inch?

Check the carrier bearing and ensure it is bolted down mounted even & perpendicular, mine was mounted canted. Look at the bolts and bolt holes and see if it looks squared up.

[TruckerMatt]

A carrier bearing mounted crooked and not perpendicular will make your truck shake, rattle, hop and bounce. Especially while running bobtail. Lay directly under the Carrier Bearing and look at the mounting bolts. Measure them. Are they even on both sides! Tight? Miss matched bolts? Lazy shops just slap them on charge you $ and yell next!

[Chamberpains]

I like TruckerMatt's run down. Just a couple more things. Put the small hammer away. Thats for your lawn mower. It's a tractor you need big tools. Get a BFH, Big F'in Hammer. Don't crush things but give them a thump. Some thing won't move or rattle without a healthy whack. If it breaks or moves, then it was definitely gonna break or move going down the road.
Also get a very large pry bar and a 2nd set of eyes to check your u-joints, carrier bearing and engine mounts. Your hand will only expose very worn out things. You need some leverage to check for the starts of things going wrong.
Rawze learned the hard way of not catching a driveline issue soon enough. You'll have to find that story. Its a good read. That was probably one of the worst driveline failure messes I've heard of. Im gonna venture a guess that it was not from a lack of looking, but from not putting enough pressure on things to expose the little things. But thats only a guess. He may have more insight in to it.

Also have an oil sample pulled from trans and both rears. Sounds like you can very easily have something going in any of them. Rears failing often make scratching noises.

[alborz]

I have same problem and I learned a lot
Do all your drive tires have similar thread Dept?
If you feel a cyclic vibration or sound when going down hill at 60 plus MPH. And gear is in neutral then buy a angle finder and measure your drive line angles and your yokes

[aaronb]

Thanks for the replies. I also forgot to mention I replaced the torque rods and got an alignment 3 weeks ago. I just bought the truck from my boss in January. He had put 4 drive tires on the back axle when I bought it. I just replaced the other 4. I ran the 4 he put on for 30,000 miles with no noises. I put the other 4 on last Friday and then I Monday I noticed the sound. I can’t really hear the sound at 60 mph. I don’t know if it’s not there or if I just can’t hear it over wind and road noise. I can hear it from taking off up to at least 40. I’m going to check the u joints again and check the transmission and rear ends for any metal. I’ll grease everything up again.

I also forgot to mention. The clutch release bearing was getting noisy awhile back. I finally found the remote lube line had a hole in it where it went through the inspection cover. I fixed it and have been greasing it regularly and it seems to be fine.

I’ll double check the ride height. It does sound like a drivetrain alignment issue. It not doing it all the time has me confused. It doesn’t seem to do it when the truck isn’t warmed up first thing in the morning.