Pete 379 rear ride height to offset car hauler w/ blocks removed?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by adamgrahamtransport, Aug 5, 2021.

  1. adamgrahamtransport

    adamgrahamtransport Bobtail Member

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    I’ve got a 2007 Peterbilt 379 factory 290” wb with the car hauler front end and the blocks removed and low air suspension on low pro 24.5’s. It has been like this since I bought it. Put new motor and tranny in plus a new leveling valve. I’m trying to set the ride height but not having any luck. I’ve set it at factory recommend setting and it shifts great but I have a rattle in the shifter accelerating and a growl going down hill with it gear at highway speeds. Does anyone have a correct setting for ride height to offset the new angles because I can’t find a good setting that doesn’t growl one way or another?
     

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  3. pavrom

    pavrom Road Train Member

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  4. Roberts450

    Roberts450 Road Train Member

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    You should set the ride height so that its close to center of the suspensions travel and so the frame is level. Then bust out your trusty dusty angle finder and adjust the shims on the rear ends, carrier bearings and engine mounts so that the angle of the dangle is correct.
     
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  5. lester

    lester Road Train Member

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    I'd find a good driveline shop or alignment shop. With the front end so low you might not be able to get the angles correct with rode height alone. Or at least not a setting that isn't to close to the stops
     
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  6. Don379

    Don379 Medium Load Member

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    Those factory settings are for basically trucks that are brand new with no wear and stock wheels and parts. Once things wear out, you have to use a drive line analyzer and go from there. I have one which cost like 300 bucks. Anyhow, your air trac wear pads are also wore out unless someone replaced them. Those change pinion geometry significantly.
    Anyhow, to get you going, just measure from the centerline of your rear axle to the bottom of the frame. If you have it set at factory specs, you are probably seeing around 11”. And of course that is waaaayyy to high for you and causing all that noise up through shifter. Knock that setting down to about 10 1/4” and take truck for a ride. Noise should be totally gone.
    You might even have to bring it even lower. If you don’t hav anymore adjustment, you gonna have to cut down the stationary rod a little. Or even better yet, make an adjustable one which people have done
     
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  7. adamgrahamtransport

    adamgrahamtransport Bobtail Member

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    I cranked it all the way up this morning which put me at 9.5” between the drives and it took the growl away and most of the chatter in the shifter. Leveling valve went bad while it was in the shop getting the motor and tranny swapped so that is why I don’t know what it was set at before. I’ve had the truck for 3 years and have never had this issue until now so I’m guessing the new motor mounts have put the driveline at a different angle than before with the old worn out ones. If I go any higher I’ll be able to put a fist between my tires and rear fenders and it will look ridiculous so off to the driveline shop I go. Thanks for the help!
     
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  8. spsauerland

    spsauerland Road Train Member

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    What suspension and how are you taking your measurements?
     
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  9. adamgrahamtransport

    adamgrahamtransport Bobtail Member

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    Low air and taking measurements from Peterbilt’s bulletin.
     

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  10. spsauerland

    spsauerland Road Train Member

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    8.5" is the loaded height, 8 3/4" unladen. You said engine was replaced, was engine put back @ original angle? Pete used washers as shims on rubber mounts to set engine @ 2°or 2.5°, which ever build calls for. Also, driveshaft was out, is it in original phase?
     
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  11. Don379

    Don379 Medium Load Member

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    sorry guys. i dont know why in my mind i thought air trac.
     
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