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Re: [GMCnet] New airbags [message #136564 is a reply to message #136562]

Fri, 29 July 2011 11:03

Dennis S

Messages: 3046
Registered: November 2005

Karma: 2

Senior Member

Mark or anyone else who may have one,

Do you still have the end of the airbag that held the fill valve? If you have no need, I have a good bag that I keep here for a spare/loaner -- but it is missing the fill valve.

Happy to pay shipping.

Dennis

Dennis Sexton
73 GMC
Germantown, TN 38138-2066
USA

-----Original Message-----
From: Mark Grueninger <markgrue@hotmail.com>
To: gmclist <gmclist@temp.gmcnet.org>
Sent: Fri, Jul 29, 2011 10:54 am
Subject: Re: [GMCnet] New airbags

The shocks are on my TO DO list not at the top but close. I like the quality
f the bilstiens we use on our dirt late model stock car so I will probably go
ith them. Different animal I know but I would think the quality is still
here. I will see. I see Jimk has them so I will more then likely get them
rom him. I intend to get some adjustable links for the rear ride height and
ee what i can do with the front torsion bars to get the ride height in line.
ave 1 more camping trip in august then will start working on it. I think you
re really close with the rear height numbers. Thats about what i figured.
hanks for your input I appreciate it.
Mark

obert Mueller wrote on Fri, 29 July 2011 09:41
Mark,

The ride height for the rear is specified as 11 11/16" +/- 1/4" from the
ground to the top of the oval slot in the frame (MM X-7525 Page 3-34 Fig 70
Checking Vehicle Ride Height.)

From memory: the frame is 6" tall and the slot is about 3/4" "high."

Here's the ride height math for your GMC:

8 3/4" = Ground to bottom of frame
3 " = Distance from bottom of frame to middle of adjustment slot
3/8" = Distance from middle to the top of the slot (3/4" divided by 1/2)
12 1/8 = Ride height

If I've got all my figures right I agree that you're a bit too high. This is
what I thought when I saw in your pictures that the bag mounting flanges on
the bogie arms were not parallel but a bit spread apart at ride height. It
has been noted on the GMCnet that at the correct ride height you can draw a
straight line from the rear wheel spindle center to middle wheel spindle
center, it will intersect the center of the bogie pins; and the bag mounting
flanges will be parallel.

You note below that you need to drop your ride height by about 3/4" that
would result in a ride height setting of about 11 5/8" which is within spec.
BTW having the rear a bit low will increase caster (marginally) and improve
handling.

On to the shock absorbers; I suspect that the shocks you have on the rear of
your GMC are for a car or truck and not a GMC.

I reviewed the presentation that Manny Trovao made at the first GMC
Convention I attended (Santa Rosa 2008) and noted the following:

Quote:
Shock absorbers work on the principle of fluid displacement on both the
compression and extension cycle. A typical car or light truck will have more
resistance during its extension cycle then its compression cycle. The
compression cycle controls the motion of a vehicle's unsprung weight, while
extension controls the heavier sprung weight.

On our motorhomes, the front shock has more resistance on the compression
cycle than on the extension cycle. On the rear, it's the opposite, it has
more resistance on the extension cycle than on the compression cycle.
Unquote

A bit further along in the presentation he has photos of shocks that have
been cutaway to show their innards. They are AC-Delco, Caspro, KYB, and
Bilstein.

Under the picture of the AC-Delco shock he states:

Quote
This is the original AC/Delco that came with the Motorhome. It's a twin tube
design. Inner tube chamber. It is no longer made
Unquote

If you are a member of GMCMI you can click on the link below; log in and
review the whole presentation:

http://www.gmcmi.com/mem-bers/TechHandouts/GMC_Shocks.pdf

I have only been a GMC owner and GMCnet member for four years and to date I
have never heard anyone note that they had "new looking" AC-Delco shocks on
their GMC. AFAIK the only shocks currently available for the GMC are made by
KYB or Bilstein.

In discovered all of this because when I drove The Blue Streak from Mudgee
(country NSW) back to Sydney and it was all over the road. During my
research on how to fix it I discovered there was a bunch of stuff wrong with
the front end and on the rear end the shocks that a PO had installed were
from a car.

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

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ark Grueninger 76 Palm Beach
almeyer IL
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Dennis S
73 Painted Desert 230
Memphis TN Metro