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RVing message boards => Bus Conversions, Buses => Topic started by: VelvetLounger on November 30, 2017, 02:15:22 PM

Title: Rear suspension question
Post by: VelvetLounger on November 30, 2017, 02:15:22 PM
Hi. I recently bought a PD4106. Im having an issue with the rear suspension. Even when the air bags have no air pressure left the right rear side continues to be elevated way higher than normal. This is also true when there is pressure. The right rear is always much higher. I know nothing about air suspension, but I guess thats my next thing to learn. Any ideas on what this could be? I can provide photos if that helps.
Title: Re: Rear suspension question
Post by: Ken & Sheila on November 30, 2017, 03:39:49 PM
I'm no expert, but a typical air suspension had 3 ride height adjusters. Either 2 in the front and one in the back or 2 in the back and one in the front. Ride height being out of adjustment could explain your situation when the air bags are inflated, but when the air is completely let out the coach should go down to the stops on both sides. This may not be perfectly level depending on weight balance the how level the ground is, but it should be close. It would seem that something is preventing the right side from going down to the stops. You need to have the rear suspension inspected. Sorry, I know this isn't much help.
Title: Re: Rear suspension question
Post by: Utclmjmpr on November 30, 2017, 04:40:23 PM
 Your 06 has the two height leveling valves in the back,,look for a vertical rod (about 3/8 diameter) hooked to a horizontal arm in front of the axle housing at each end,,,you can "adjust" by bending one or the other to adjust the end to end length of the rod..
   By bowing the rod, you shorten the end to end length,,and IF,, the horizontal "arm" is mounted at the top,, you will lower the coach
 ON THAT SIDE.. The reverse is to straighten the rod to lift the coach ON THAT SIDE

If sometime in its life the valves have been replaced with late generation types,, you can adjust the rods at one end by sliding the rod up or down after loosening the clamp  DON'T DO THIS WHILE UNDERNEITH THE COACH WITHOUT BLOCKING!!! >>>Dan
Which year is the coach?? Mine was a 62 and I converted and owned it 14 years..
Title: Re: Rear suspension question
Post by: ronster on December 17, 2017, 09:19:13 PM
The airbag on the high side could have been replaced with one that fits but has a different stand inside it.Had same problem on rear or a dump trailer.Try to get proper number from mfg or a forum.
Title: Re: Rear suspension question
Post by: Gary RV_Wizard on December 18, 2017, 08:14:03 AM
The ride height control arms have no effect once the air is dumped from the suspension, so I'm guessing the problem is that the air doesn't dump or it's an incorrect model of airbag (per ronster's comment).  I'm not familiar with the specifics of your air suspension, so not sure what to suggest about dump valving. You may have two problems - ride height incorrect (very common) plus no dump.
Title: Re: Rear suspension question
Post by: boatbuilder on December 18, 2017, 08:28:48 AM
Some airbags have internal bump stops. It could be as simple as one bag has been replaced and has a different bump stop height.
Title: Re: Rear suspension question
Post by: Utclmjmpr on December 23, 2017, 01:05:48 PM
 The bump stops on an 4106 are external,, the air bags are either firestone or goodyear..(same design, different rubber compound) The 06 also did not have a "dump" system,, if you wanted to release air you had to pump the brakes with the engine off, or pull an air tank lanyard.
  If an air system is in good condition, it can hold air for months,, and yes one side can bleed down without the other...I still say the rear height control valves need adjusting and its not difficult.  You really need a manual. Be prepared for about $75.00 for a used or reprint..>>>Dan   Check my signature line. Western GM Coach is a 30 year old GMC only club, and over the years up to 250 member owners involved in the conversion and operation of GM coaches..

Many converted coaches have an after market 4 point leveling system installed..Do you have, (on your dash or close) a panel with 4 push-pull buttons with a small  air gauge above each?? That would be a 4 point and you can adjust each corner of the coach individually.  If you have this system, the automatic system will be dis-abled and you will have to level to a known pressure at each gauge each time you air up..
Title: Re: Rear suspension question
Post by: Lou Schneider on December 23, 2017, 06:46:59 PM


Yes, please make sure the bus is adequately supported any time you're underneath it!

We've already lost one Forum member when the air suspension collapsed while he was working underneath his rig.
Title: Re: Rear suspension question
Post by: Utclmjmpr on December 25, 2017, 02:00:42 PM
 The correct ride height is 3.5 inches from bump stop to underside of frame.>>>D