Is the 377 a light duty rig???

Discussion in 'Peterbilt Forum' started by Autoped, May 20, 2011.

  1. Autoped

    Autoped Bobtail Member

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    May 20, 2011
    Houston, TX
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    I apologize if I offend anyone with this, but I was heading down to Laredo, TX to haul some machinery when my KW encountered some engine problems. I was able to get my company to send me a truck they had just bought (1999 Peterbilt 377) to swap under my trailer. I left my K-whopper at the temporary drop yard where I was staying and headed out to pick up one of the machines. I had loaded a 50K# mulcher (oversized) onto my 20K# trailer (no kidding), hooked up, went to lifting the lowboy off the ground, and I ended up bottoming out the 377. The axles were sitting on the frame, the airbags were filling up with air and NOT expanding up, but out. After about 4 minutes of watching the bags swell up like balloons with no lift, I decided to call the haul off, and contract an outside company to haul the machine/trailer. The 377 they sent me is an straight 8 speed with a detroit 60 series. The GVWR on the truck is 50K, and the trailer is almost triple that at 132,500#. The other truck was a freight shaker, which picked the load up almost immediately, and my KW won't even breathe when picking up that same machine/trailer combo. I'm new to the trucking industry, but been around this line of work for a while, and I have never seen something like this happen. Is this 377 a light duty truck? Was I doing something wrong with this load or was the truck just too undersized and underpowered to handle the load? This is bugging me, so any input on this issue is greatly appreciated. The guy who sold it to my company told them he had hauled 80K# before, and said I wasn't doing something right, but with the way it acted, I think he just told them anything to sell the truck. Once again, thanks for any help about my issue with this truck...
     
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  3. Krooser

    Krooser Road Train Member

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    Jul 25, 2010
    Wisconsin
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    The 377 can be spec'd the same as a 379... I think the air leveling valve was not adjusted correctly.

    My son has a 377 and it does a good job.
     
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  4. freightlinerman

    freightlinerman Road Train Member

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    Mar 4, 2011
    Florida
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    Sound's like the truck was over loaded. If the truck bottomed out the air bags looked like balloons, the ride height was probably set just fine. In fact, it was probably trying to air up but couldn't because of the weight and I believe there is a pressure protection valve which will open when pressures get too high. I've seen a single axle tractor, with a tandem axle flat bed with a gross of 80k pounds come in to the fuel island at the truck rental place and the tires looked like they were going to explode.

    The driver was such a moron he asked me to check the tires because he thought they were low on air. I didn't have to check the tires to tell the moron that he was grossly over loaded, he had to make the turn and move around at almost a crawl in 2nd gear. The air bags were dumping out of the leveling valve. Long story short, he had to rent a tandem axle to do the job and got pulled in at the weigh station and I got an over weight citation here in Florida, I believe it was 82k.

    I don't know what the deal was with your truck, but I would guess that you had too much weight on the drives. Let's face it, you could be FULLY loaded and park the truck over night and have an air leak in the air bags, and the truck would not bottom out with a gross of 80k. Just doesn't add up.
     
  5. jr-transport

    jr-transport Light Load Member

    that doesnt sound right, i have an 05 379x with flex air, which is a light spec (38 000lb) susbension and I haul 140 000lbs out of the bush, loaded heavy on the drives without any trouble. I beleive when I rolled ont the scales my tractor weights were about 65-70k . it would bottom out on bumps, but wasnt any real trouble.

    What suspension did it have? if its a 99, it will be most likely a Low Air Leaf, which is a 40k suspension. but it could also be Air leaf or Air Trac. If its Air Trac, it should hold it no problem.
    If it was unable to lift it then there was a problem other than being over loaded.
     
    Last edited: May 29, 2011
  6. sr_smyth

    sr_smyth Bobtail Member

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    May 30, 2011
    Terrace BC
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    We used to supply 377's to a fleet of 50 trucks that pulled wood chips up to 63,500 kgs (139,700 lbs) all day, 6 days a week, 24 hours a day. As the previous fellow suggested, you can spec them as heavy as a 379, Just dont try it with Flexair suspension.
     
  7. Krooser

    Krooser Road Train Member

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    Jul 25, 2010
    Wisconsin
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    I believe the axle rating is what determines the load capacity rather than the suspension... The Eaton rears that are standard on today's Petes start at 40,000 and go up from there.

    My son's '87 377 had Spicer rears in AirTrac...

    I've had 48K on my drives with my 379's AirLeaf.
     
  8. jr-transport

    jr-transport Light Load Member

    i checked my papers, flex air is a 38 000 lb suspension, and I have super-40 eaton rears.
    the new LAL is available 40k and 46k models, Air Trac comes in a couple of variants as well. Heaven forbid it all be easy to remember;)
     
  9. Krooser

    Krooser Road Train Member

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    Wisconsin
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    Pete offers 11 different rear suspensions for the 389...
     
  10. jr-transport

    jr-transport Light Load Member

    Wow LOL! i got me some readin' to do!
     
  11. BretStep

    BretStep Light Load Member

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    Sep 27, 2011
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    Im not an expert, but i do know tht the only difference between a 377 and 379 is the lower hood and more aerodynamic front end.
     
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