[GMCnet] Ride height
Work Jerry
You can only measure ride height via the slots cut in the frame front and rear. From the TOP of the front slot (near where the sub frame bolts to the main part of the frame) to level ground needs to be 13 1/8" +- 1/4. That has to be set via the torsion bar adjuster bolts WHICH CAN ONLY BE TURNED AFTER YOU INSTAL AND PROPERLY USE THE SPECIAL TORSION BAR UNLOADING TOOL. If you try to adjust ride height via the adjuster bolts themselves the factory manual says you will likely strip the bolt threads or the threads in the adjuster nuts. If this does not make sense to you, then do nothing. Ask for help as the torsion bars store an enormous amount of energy which can be dangerous if not controlled properly. Only after the front ride height is set can you adjust the rear ride height to be 11 11/16 +- 1/4 from the top of the rear slots (look on the frame under the rear compartment) to level ground. That adjustment is made via changing the rear ride height adjustment link if yo
ur system remains stock and is in proper working condition. No short cuts here. Follow the factory manual which you can download from Billy M's site. Hope this helps and be careful.
Jerry
Jerry and Sharon Work
78 Royale rear lounge
Kerby, OR
glw...@mac.com
http://jerrywork.com
541-592-5360
Message: 8
Date: Fri, 05 Aug 2011 15:07:12 -0500
From: sgltrac <sgl...@gmail.com>
Subject: [GMCnet] ride height
To: gmc...@temp.gmcnet.org
Message-ID: <21996.4...@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"
I have a 77 Royale with electro level suspension(one compressor mounted behind drivers side wheel well rear. I believe this is the electro level one?)My controller operates the pump on manual raise and lower and will level the coach when left on auto. The problem is while it appears to level side to side in auto mode it shuts off when the rear of the coach is about 2 inches lower than the front when measured from the straight section of the frame behind the rear wheels and the furthest horizonal part of the frame towards the front. What is the simplest way to adjust system to get the rear to come all the way up to true level?
Thanks,
--
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
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t panel meets upper aluminum left side panel. Then I can paint the rest of this thing. Final suspension setting to come later
Sully
77 royale
Sent from my Verizon Wireless BlackBerry
Charles Boyd
[quote title=sgltrac wrote on Sat, 06 August 2011 13:25]It would be nice if the generator drawer bracket diddnt cover the rear oval measurement point on the left rear. I measured from the front holes after checking tire pressures and came up with 15 1/8" LF,14 5/8" RF, 12" RR and approx 11 3/4" LR(taking the difference of height from bottom of rt rail to same location on left rear rail and subtracting from RR height at measurement hole). The coach has been sitting and jacked up and set down a couple of times from the left front under body braces in an attempt to straighten some sagging floor out riggers under the drivers foot area. I understand from reading other posts that I may need to drive the rig around a little before it will sit where it is "happy".
Sir: I would suggest adjusting the rears on a level surface then cut 2) 4x4 blocks that sit under the frame at the race track holes at ride height. Then using the blocks dump the air on the rears and then set the front ride height. Drive and recheck.
--
C. Boyd
76 Crestmont by Midas
East Tennessee
Charles Boyd
[quote title=C Boyd wrote on Sat, 06 August 2011 13:49]sgltrac wrote on Sat, 06 August 2011 13:25
> It would be nice if the generator drawer bracket diddnt cover the rear oval measurement point on the left rear. I measured from the front holes after checking tire pressures and came up with 15 1/8" LF,14 5/8" RF, 12" RR and approx 11 3/4" LR(taking the difference of height from bottom of rt rail to same location on left rear rail and subtracting from RR height at measurement hole). The coach has been sitting and jacked up and set down a couple of times from the left front under body braces in an attempt to straighten some sagging floor out riggers under the drivers foot area. I understand from reading other posts that I may need to drive the rig around a little before it will sit where it is "happy".
>
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> Sir: I would suggest adjusting the rears on a level surface then cut 2) 4x4 blocks that sit under the frame at the race track holes at ride height. Then using the blocks dump the air on the rears and then set the front ride height. Drive and recheck.
PS: 6 turns on the front torque rod adjusting bolt is about 1".
sgl...@gmail.com
Sully
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: Charles Boyd <covere...@comcast.net>
Sender: gmclist...@temp.gmcnet.org
Date: Sat, 06 Aug 2011 12:52:49
To: <gmc...@temp.gmcnet.org>
Reply-To: gmc...@temp.gmcnet.org
Chuck Garton
November 1977, I had purchased a 1974 GMC Sequoia 26' from Reynolds
Buick in West Covina. CA. Reynolds Buick was a big GMC Motorhome
dealer with a very well equipped shop. The coach had 25,000 miles on
it and paperwork showing a recent 6 wheel alignment and ride height
adjust. It had the 16.5" wheels and bias ply tires. The ride home (I
live 125 miles north of West Covina, CA.) was "bumpy" and the way home
included a run up Cajon Pass on I-15 and I had no problems getting
home. I had bought a new 1967 Toronado, so I had some experience with
the drive train. I even had a torsion bar unloader.
After obtaining a set of maintenance manuals, I started with an oil
change. While under the coach and inspecting everything, I noticed it
had replacement lower ball Joints. Then, looking at the torsion bar
adjusting bolts, I found that the right adjusting bolt was tightened
all the way in. Looking at the left adjuster bolt I discovered it was
missing! I just happened to have a spare adjusting bolt.
I finished the oil change and drove the coach and returned to my level
driveway. I checked the ride height according to the manual, and it
was within a 1/16" of correct on all four measurement sites (the Onan
covered the left rear slot, but I worked around this).
After some thought, I raised the back end and marked the frame in the
center of the coach, then lowered it back down and drove 4 or 5 miles,
then back in the driveway. Next I measured between the frame center
and ground. Then to the wood pile and found a round log whos diameter
was the same as the frame to ground measurement. I placed the log
under frame center. Inside the coach, I let 25 lbs of air out of each
air bag. Then I measured the front ride height and found the left side
to be 1.25" low and the right side 3/4" high.
Using the unloader, I adjusted the torsion bars to the correct height.
Then aired up the back to automatic ride height and drove around for a
few miles, the back to the driveway, put the logback in frame center,
let out 25 lbs of air from the air bags and measured front ride height
again. It was closer, but not correct. Re-adjusted ride hieght bact to
specs etc. I had to do about 6 adjustings before the front ride height
was correct after a drive.
The rear ride height adjustment went quicker. It only took two
adjustments to get all four adjustments correct.
The improvement in ride and handling was great, even with the steel wheels.
This exercise convinced me that the rear suspension controls the front
ride hieght side to side.
Chuck Garton
77 Kingsley 455
Ridgecrest, CA
Ken Burton
We do something similar to you and Chuck. I cut 4 adjustment blocks out of 2x2"s and 2x4"s (I got this idea after watching Jim K. check every GMC that was on his hoist in his shop for repairs.)
The reason for the 2x2 and 2x4 difference was to keep from confusing which blocks went where. The blocks match exactly the rear and front ride heights to the bottom of the frame. I have found that just checking height does not work because anything that changes on the coach rear is automatically adjusted for by the air pressure level in the bags.
So what I do to the bags is raise the coach, slide the coach adjustment blocks under the frame, and drop the coach on them until they put a slight amount of weight on them. This locks the rears in place at the correct height and takes the rear movement out of the picture. Then we adjust the fronts for the correct heights. Finally after the front height is correct we put the fronts on a set of scales and check for close to equal loading between the two front wheels. I try to get them within 50 to 75 pounds of each other. I have seen where the front heights will be correct and the weight will be 300 - 400 pounds different. As you crank on the bars to correct this imbalance the weights will change without any movement in ride height. What is happening is one side it taking more weight but the bar is flexing more so the height remains the same. You are correcting this problem.
After the front is done (correct height and near equal weight) go drive it and come back. Stop on a level spot and check the front again using the above procedure.
It may take more than one adjustment process to get those perfect.
Once the fronts are done then measure adjust the rears and readjust as necessary. Only measure and adjust the rears after driving the coach so the leveling switches have had time to find their true spot.
When we weighed the coaches at the DuQuoin rally we also used these same blocks to tell the people where their ride heights were set along with the weights on each wheel.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Chuck Garton
access to scales is one and his scale is raised around the edges....
Chuck Garton