Bad differential??

Discussion in 'Peterbilt Forum' started by Jennyspete, Aug 1, 2024.

  1. Jennyspete

    Jennyspete Light Load Member

    58
    32
    Apr 3, 2010
    ma
    0
    I've got a '99 Pete 379. About 3 weeks ago I got loaded at one if my usual customers. I usually haul a little heavy 92k+. There's a steep short driveway to climb to get to street level. When I'm backed into the dock my trailer is flat but the tractor is already headed up the driveway.
    I've been there 1000 times, but this time I started spinning a wheel then heard a loud snap. I backed up as much as I could , timed traffic so I didn't have to stop on the hill and put my foot in it and made it out with no issues.
    Truck developed a bounce. If I was on the low side of the rpm's for the gear I was in (1200-1300) it would bounce until accelerated or shifted.
    Bobtailing one day i turned down a street (90 degree turn) and i though i was going to get bounced out of my seat. It stopped when i was straight.

    Then I was pulling a flatbed ( something I don't normally do) I strapped down the totes I had on, but being 5'8" and 135lbs I can pretty much hang off the winch bar and not move it. So once I left I was paying more attention to my trailer than normal because I didn't trust my strapping job. That's when I noticed the nose of the trailer walking around a lot. The next day I had my reefer back on and was headed home empty and it was bouncing a lot. If I accelerated when it was bouncing, the bouncing stopped. If I accelerated when it was fine then it would start bouncing.
    Got home had mechanic pull front axles. They were not broken.
    Rear diff had no metal
    Front diff had miniscule pieces of metal.
    Found center pin on left front springs was broken and U bolt was loose. Axles were out of alignment by about 2".
    Hoping for a miracle we replaced center pin, tightened u bolts and realigned . Axles are out less than 1/4" now. Took it for a ride tonight with empty trailer. Symptoms are all still there. The bouncing, trailer moving and it's harder to handle a little bit. Seems like I'm having to move the steering wheel back and forth more but maybe that's from the trailer moving.
    There is no grinding or clunking noises but I'm still going with a bad differential.
    Bobtailing is easier but that's it for improvement before it acted like the inter axle lock was in. But I haven't used that in months.
    I know a bad diff can cause a vibration but I haven't noticed that only the bouncing.
    So before I tear this down I thought I'd reach out and see if anyone had any other ideas or things I should look at while it's apart.
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. circle h

    circle h Light Load Member

    240
    374
    Oct 22, 2020
    0
    Driveshaft carrier bearing, maybe.
     
  4. Jennyspete

    Jennyspete Light Load Member

    58
    32
    Apr 3, 2010
    ma
    0
    Ok I had not thought of that. This truck has had a lot of drive line issues. I took all drive shafts out and had them balanced altogether. Haven't had any problems since so I was not thinking about that at all. That's easy enough to check. Thanks
     
  5. Big Road Skateboard

    Big Road Skateboard Road Train Member

    4,981
    24,211
    May 2, 2021
    0
    Sounds like your truck suspension ride height may be set too high
     
    Oxbow Thanks this.
  6. Ridgeline

    Ridgeline Road Train Member

    21,363
    106,764
    Dec 18, 2011
    Michigan
    0
    I second that, I never heard of a bad diff causing any bouncing.
     
    Jennyspete Thanks this.
  7. Oxbow

    Oxbow Road Train Member

    11,141
    112,534
    Nov 24, 2015
    Idaho
    0
    She did say that it happened when cornering, which makes me wonder about the differential or power divider being locked in.
     
    Big Road Skateboard Thanks this.
  8. Ridgeline

    Ridgeline Road Train Member

    21,363
    106,764
    Dec 18, 2011
    Michigan
    0
    could be but I am thinking that either a strut arm is bent or broken or something else seeing she mentioned that she heard a snap.
     
    Oxbow and Big Road Skateboard Thank this.
  9. Diesel Dave

    Diesel Dave Last Few of the OUTLAWS

    7,954
    18,473
    Jan 20, 2010
    Hesperia, Ca.
    0
    Seems she’s been having issues all along similar, has older threads started.
     
  10. Big Road Skateboard

    Big Road Skateboard Road Train Member

    4,981
    24,211
    May 2, 2021
    0
    Hard to say what the snap was. First thought of course is axle, but they ruled that out.

    I know it sounds counterintuitive, but it has all the symtoms of overinflated air bags.

    Loss of traction, feels loose, bouncing during cornering, all can be caused by that.

    I would expect tires locking up during a power divider issue. Then again, that could definitely cause a hop, or bounce during cornering. But not the loose feeling.
     
    Oxbow, Jennyspete and Diesel Dave Thank this.
  11. Jennyspete

    Jennyspete Light Load Member

    58
    32
    Apr 3, 2010
    ma
    0
    This could be a very real possibility. With all the driveline issues I've had that has been mentioned before. I watched a video from Peterbilt that shows how to check ride height. It shows to run all the air out of the system. My mechanic did not do that. I showed the video to my mechanic and he told me it didn't matter. He did adjust it a bit. However, I think I should take it to Peterbilt and have them do it. I'm pretty sure it does matter.
     
    Oxbow Thanks this.
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.