379 peterbilt problems

no pulsing with brakes but I put new brakes and drums anyway. No balance on tires but I have centramatics and I tried taking them off... even worse. Same thing with the old tires anyway. They were worn exceptionally smooth and even when I took them off. I may be on to something now though. I don't have "Spring Eye Shims" on my springs and I should so I am going to put them and see what happens. Thanks for the input. I need all the help I can get!

 

If it got worse when you removed your centramatics than they must be quelling a wheel end imbalance. I would have the drives spin balanced and watch them get spun on the machine. Don't except any runout. If they can't remedy runout by breaking down and re-mounting the tire properly than take a closer look at just the wheel.

It also wouldn't hurt to have them remounted using centering pins. http://www.tru-bal.com/
Eliminating any hub wear and centering the entire assembly.

 

Is it all the time ? under load and bobtail ? just certain speeds ? axcelerating and deceleration ?

 

Just an idea, stand behind the rear wheel and check to see if one axle is off to the left and the other off to the right.

 

All the time at any speed, loaded, empty, or bobtail.

 

No, I am convinced it has nothing to do with the wheels. It is definatly a suspension problem. I've checked for run out and looked at the axles and had it aligned. All is good there. It even shakes (At the same frequency) going down my street at 20 mph.

 

It sounds like a possible driveshaft angle problem or an engine misfire maybe. Just guessing.

 

What suspension do you have ?
If it's flex air it could be spring wrap.
http://www.mdalign.com/techbulletins/1178380368.pdf

The fact that the frequency doesn't change is odd.
This is a tough one.

 

low air leaf

 

Ever hear of a "Spring eye shim"? Peterbilt part number is 03-05192. I don't have this part.

http://www.truckcomponentsonline.com/LOW-MOUNT-AIR-LEAF-SINGLETANDEM-AXLE-REAR-AIR_c_500.html