'99 379 rear airbag height.

Its got my back driveline way out of specs causing major vibration

 

I'm stumped. Lol. I understand your frustration because I had a similar issue on my 05. Turned out my leveling valve had a small crack in it so it didn't hold steady pressure or ride height. Did you by chance measure from the flat ground to the bottom of the frame?

 

No i was going to do that tomorrow when on good concrete. By looking from the side of truck the front of the frame is quite a bit lower than back of the truck. When i purchased, they had front lowered on 2" blocks. I had 4" block put back in raising back up, but it still don't set high enough to level out the frame on both rears. Like i said most of frame pressure sets on front drives.

 

Right. If I measure right in front of both axles, there's an inch or so difference from the ground to the frame. I'm not sure what difference tires should make, if any, but I'm on 11r22.5s and from flat ground to the bottom of the frame , just in front of the rear spring hanger, is pretty much exactly 31 3/4in with an empty trailer. Pete goes 1/4in higher bobtail, 1/4in lower loaded.

 

All 4 bags should be the same pressure. DO NOT confuse pressure with height. If the steer axle is too low obviously the rearmost drive axle will have the bags extended further. Jamming more air in the front bags isn't going to correct the issue.

 

I understand and agree completely, but with no changes to the rear, won't the leveling valve and the system in general, attempt to compensate to maintain ride height? I'm not challenging you, just checking my line of thinking.

 

Equal pressure means equal force. The front drive isn't carrying any more weight than the rear.

 

That's correct. Front needs to come up. Correct?

 

I know you put the 4in blocks back in, but are the front springs factory? Some guys get recurved springs for lowering... some dumb ones remove a spring or two for whatever reason too.

 

What about smaller steer tires?