Home » Public Forums » GMCnet » Body/frame isolator pads
| Body/frame isolator pads [message #168068] |
Mon, 30 April 2012 16:50  |
bryant374
Messages: 563
Registered: May 2004
Location: Pleasant Valley, NY 12569
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I am in the process of replacing the body/frame isolator pads. Thanks to those that did this before me and provided instructions that were very helpful. All new pads are in place but I am having a problem with the rear isolator body supports. I have at least a 1/4" gap to fill. Got the nuts off the large bolts but having difficulty in removing the top rubber isolator (donut) from the bolt, allowing me to put washers on the bolt to take up the gap. Was going to put washers under the 4 bolts in the aluminum plate but those bolts are too short and stuck in that plate also.
Suggestions on what you did appreciated.
Thanks,
Bill
Bill Bryant
PO 1976~PB (owned 34 years)
1914 Ford (owned 70 years)
1965 Corvette (owned 39 years)
GMC Motorhome History
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| Re: [GMCnet] Body/frame isolator pads [message #168076 is a reply to message #168068] |
Mon, 30 April 2012 17:52  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Bill,
I'm having trouble picturing what you describe. Could you take a snapshot of it? Still, I doubt I could offer much help, but if I'm having trouble understanding it, maybe others are too.
Then again it wouldn't be the first time I'm the only one who doesn't get it!
Larry Davick
Fremont, California
The Mystery Machine
'76 (ish) Palm Beach
----- Original Message -----
From: "Bill Bryant" <bryant374@earthlink.net>
To: gmclist@temp.gmcnet.org
Sent: Monday, April 30, 2012 2:50:08 PM
Subject: [GMCnet] Body/frame isolator pads
I am in the process of replacing the body/frame isolator pads. Thanks to those that did this before me and provided instructions that were very helpful. All new pads are in place but I am having a problem with the rear isolator body supports. I have at least a 1/4" gap to fill. Got the nuts off the large bolts but having difficulty in removing the top rubber isolator (donut) from the bolt, allowing me to put washers on the bolt to take up the gap. Was going to put washers under the 4 bolts in the aluminum plate but those bolts are too short and stuck in that plate also.
Suggestions on what you did appreciated.
Thanks,
Bill
--
Bill Bryant
1976~PB
1914 Ford
1965 Corvette
GMC MH History CD
GMC Showroom Films DVD
http://bdub.net/billbryant/
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] Body/frame isolator pads [message #168081 is a reply to message #168068] |
Mon, 30 April 2012 18:17 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Bill,
Ref Parts Book 78Z - Page 23-76 Figure 23.090 - BODY MOUNTING
The following assumes that you have tried to spin the large bolt (Key 8A)
out using a ratchet wrench and hammering that bolt out from the bottom using
a drift.
If you have an air driven wrench or impact wrench you could try using it to
spin the large bolt (Key 8A) in the counter clockwise direction while
holding the upper isolator pad you might get lucky and it'll spin out.
OR
If you have a pneumatic impact hammer you could use it to hammer the bolt
out from the bottom.
Regards,
Rob M.
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Bill Bryant
Sent: Tuesday, May 01, 2012 7:50 AM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Body/frame isolator pads
I am in the process of replacing the body/frame isolator pads. Thanks to
those that did this before me and provided instructions that were very
helpful. All new pads are in place but I am having a problem with the rear
isolator body supports. I have at least a 1/4" gap to fill. Got the nuts
off the large bolts but having difficulty in removing the top rubber
isolator (donut) from the bolt, allowing me to put washers on the bolt to
take up the gap. Was going to put washers under the 4 bolts in the aluminum
plate but those bolts are too short and stuck in that plate also.
Suggestions on what you did appreciated.
Thanks,
Bill
--
Bill Bryant
1976~PB
1914 Ford
1965 Corvette
GMC MH History CD
GMC Showroom Films DVD
http://bdub.net/billbryant/
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Body/frame isolator pads [message #168082 is a reply to message #168068] |
Mon, 30 April 2012 18:35 |
Adrien G.
Messages: 474
Registered: May 2008
Location: Burns Flat, OK 73624
Karma: 1
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Bill,
Use longer bolts.
I went a different rout, I made 2 new alum mount plates of the thickness I needed.
If you space the plate, I wander if the load forces may crack the old plate, time would tell.
Adrien & Jenny Genesoto
75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild
Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6
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| Re: Body/frame isolator pads [message #168087 is a reply to message #168068] |
Mon, 30 April 2012 19:13 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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A 1/4" gap isn't too bad since I used body pads that were too thick for my coach I had to fabricate 3" by 1/2" thick square spacers out of aluminum and drill a hole in the middle for the big bolt. I believe it was a 5/8" bolt. I'd leave the 4 smaller bolts alone and install the spacer between the donut and the body. I also had room between the body and the spacer for a rubber cushion. My large original bolt was too short so I had too get 2 longer bolts at Ace hardware Home Depot and Lowe's don't have hardened bolts that size. To get the 2 large bolts out you need to put a box wrench on the head (inside the coach in the rear after you remove the 2 small panels on each side in the rear) then unscrew the nut .An impact wrench is helpful. If you don't hold the head of the bolt with a box wrench the bolt will just spin. A little bit of work but nothing like a cracked tank and ripping the slide valve out of the tank.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Body/frame isolator pads [message #168099 is a reply to message #168068] |
Mon, 30 April 2012 20:15 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Spin the nut back onto the bolt until the tip of the bolt is flush with the face of the nut. Drive the bolt upward until the nut stops upward movement. Now drive it back down til the bolt head stops it. Each cycle will kick a bunch of corrosion out until the bolt spins free. An air chisel with a planishing head works very well. You should be able to add 1/4" spacer without going to a longer bolt. I just did this same thing a month ago.
Sully
77 royale
Sent from my iPhone
On Apr 30, 2012, at 2:50 PM, Bill Bryant <bryant374@earthlink.net> wrote:
>
>
> I am in the process of replacing the body/frame isolator pads. Thanks to those that did this before me and provided instructions that were very helpful. All new pads are in place but I am having a problem with the rear isolator body supports. I have at least a 1/4" gap to fill. Got the nuts off the large bolts but having difficulty in removing the top rubber isolator (donut) from the bolt, allowing me to put washers on the bolt to take up the gap. Was going to put washers under the 4 bolts in the aluminum plate but those bolts are too short and stuck in that plate also.
>
> Suggestions on what you did appreciated.
> Thanks,
> Bill
>
>
> --
> Bill Bryant
> 1976~PB
> 1914 Ford
> 1965 Corvette
> GMC MH History CD
> GMC Showroom Films DVD
> http://bdub.net/billbryant/
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: Body/frame isolator pads [message #168132 is a reply to message #168068] |
Mon, 30 April 2012 22:37 |
bryant374
Messages: 563
Registered: May 2004
Location: Pleasant Valley, NY 12569
Karma: 1
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Senior Member |
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>
> I am in the process of replacing the body/frame isolator pads. Thanks to those that did this before me and provided instructions that were very helpful. All new pads are in place but I am having a problem with the rear isolator body supports. I have at least a 1/4" gap to fill. Got the nuts off the large bolts but having difficulty in removing the top rubber isolator (donut) from the bolt, allowing me to put washers on the bolt to take up the gap. Was going to put washers under the 4 bolts in the aluminum plate but those bolts are too short and stuck in that plate also.
>
> Suggestions on what you did appreciated.
> Thanks,
> Bill
>
>
Thanks to all for your suggestions, I should have been clearer on my specific problem as I seem to have confused some.
1. Carl Ps picture shows the problem part (top half of rubber donut (with spacer tube) that is captured between the body & frame. The large bolt must be removed before washers can be added to eliminate gap.
2. I have removed the nuts from the "large" bolts. A longer bolt is not needed.
3. I have attempted to drive the bolts out with a brass drift and hammer. Corrosion between the large bolt and the tube* inside the rubber donut appear to have them stuck together. The top donut seems to attenuate the shock of the drift against the bolt. If I can move the donut enough to get a vice grip or pipe wrench on the tube and turn the bolt head I may be able to twist loose the corrosion interface.
4. The aluminum plate (with the 4 smaller bolts) can't be removed also unless the large bolt is first removed.
* The tube inside the rubber donut controls the amount of compression the donut receives.
Hope this makes things clearer.
Thanks again,
Bill
Bill Bryant
PO 1976~PB (owned 34 years)
1914 Ford (owned 70 years)
1965 Corvette (owned 39 years)
GMC Motorhome History
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| Re: Body/frame isolator pads [message #168157 is a reply to message #168145] |
Tue, 01 May 2012 10:12 |
bryant374
Messages: 563
Registered: May 2004
Location: Pleasant Valley, NY 12569
Karma: 1
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rf_burns
I loosened the 4 smaller bolts that hold the donut mounting plates front and rear and used slotted washers like these to take up the space there.
http://www.mcmaster.com/#slotted-washers/=hcb3n2
They look like carriage head bolts but they are not... they have a spline so you can't just take them out and space with a regular washer.
JWID
>
>
My first try was to do just that but the 4 smaller bolts are not long enough to make up the gap I have. The flat washer on the 4 bolts is needed because the bolt is in a slotted frame hole, the lock washer is needed to prevent the nut from backing off. I could use a self locking nut and eliminate the lock washer but you need the full thread depth in the nut to engage the locking surface.
If I could free up the large bolt a slotted washer between the body & the top of the rubber donut would work great. If I could free up the large bolt I could use any washer and I wouldn't have a problem :^(
My take is, "keep working on loosing the large bolt"
Thanks again.
Bill Bryant
PO 1976~PB (owned 34 years)
1914 Ford (owned 70 years)
1965 Corvette (owned 39 years)
GMC Motorhome History
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| Re: Body/frame isolator pads [message #168160 is a reply to message #168132] |
Tue, 01 May 2012 10:38 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Bill
You are probably right about the rubber donut taking up the blows trying too loosen it. I would flood the bolt from the top (inside) and the bottom with penetrating oil then place a bottle jack under the bolt and start jacking. It should break it loose. It doesn't rain around here so my bolts had no corrosion.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Body/frame isolator pads [message #168161 is a reply to message #168160] |
Tue, 01 May 2012 10:58 |
bryant374
Messages: 563
Registered: May 2004
Location: Pleasant Valley, NY 12569
Karma: 1
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Re: Body/frame isolator pads
Tue, 01 May 2012 11:38
roy1
Bill
You are probably right about the rubber donut taking up the blows trying too loosen it. I would flood the bolt from the top (inside) and the bottom with penetrating oil then place a bottle jack under the bolt and start jacking. It should break it loose. It doesn't rain around here so my bolts had no corrosion.
>
>
Great idea, thanks!
Bill Bryant
PO 1976~PB (owned 34 years)
1914 Ford (owned 70 years)
1965 Corvette (owned 39 years)
GMC Motorhome History
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| Re: [GMCnet] Body/frame isolator pads [message #168212 is a reply to message #168183] |
Tue, 01 May 2012 20:30 |
bryant374
Messages: 563
Registered: May 2004
Location: Pleasant Valley, NY 12569
Karma: 1
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Re: [GMCnet] Body/frame isolator pads
Tue, 01 May 2012 18:31
Robert Mueller
Bill,
Just got a brainstorm!
Drive the GMC down to your local muffler shop and ask them to use their air
hammers to knock the bolts out after you soak them for a few days with
penetrating oil.
Regards,
Rob M.
>
>
Thanks Rob, going to try the jack first.
Bill Bryant
PO 1976~PB (owned 34 years)
1914 Ford (owned 70 years)
1965 Corvette (owned 39 years)
GMC Motorhome History
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| Re: Body/frame isolator pads [message #168221 is a reply to message #168068] |
Tue, 01 May 2012 22:16 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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| bryant374 wrote on Mon, 30 April 2012 15:50 |
I am in the process of replacing the body/frame isolator pads. Thanks to those that did this before me and provided instructions that were very helpful. All new pads are in place but I am having a problem with the rear isolator body supports. I have at least a 1/4" gap to fill. Got the nuts off the large bolts but having difficulty in removing the top rubber isolator (donut) from the bolt, allowing me to put washers on the bolt to take up the gap. Was going to put washers under the 4 bolts in the aluminum plate but those bolts are too short and stuck in that plate also.
Suggestions on what you did appreciated.
Thanks,
Bill
|
Bill, I'm trying to get to the very basics of this. I'm wondering why the rear mounts are so far from seating. It seems on the surface that you have raised the body back up to where it needs to be. If you have that much clearnce to the rear mount, either the new pads are overly thick or the body has sagged in the middle. One thought is to pull the rear back down beyond where it wants to be right now.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Body/frame isolator pads [message #168227 is a reply to message #168221] |
Wed, 02 May 2012 00:31 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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Bob, the reason that a 1/4" needs to be added to the very rear (as well as
very front) body mounts is that the original body bushings (except the
front and rear two) were 1/4" thick pads placed between the chassis frame
and the coach floor framing. The rearmost and forward most pair of mounts
are of a more traditional body over frame design with a steel sleeve and
cap with rubber isolator to secure the chassis to the body without
transferring any controllable noise and vibration from the chassis to the
body. The body pad replacement kit (at least the one I bought from the
coop) has 1/2" pads. Well, actually they are hockey pucks cut in half
netting two body pads per puck so I guess hockey pucks are one inch plus
whatever thickness saw blade Jim B cuts them with cause all of the halves
I got in my set were damn near exactly 1/2". I have to say that I don't
know how he cuts them but if I had to cut them myself I am fairly certain I
would end up with a little more variation in thickness and probably a
damaged saw. But anyway if you add an additional 1/4" to the bulk of the
body to frame isolators which were 1/4" pads that are now broken down or in
many cases missing and the front and rear two are still in good condition
and at or very near original height then to keep the whole show in the
original plane a 1/4" would need to be added to the front and rear body
mounts.
I add as a disclaimer or an addendum that the information from which the
above declarations are based was gathered from working on 1977 Royale
26'. Your situation may and probably will vary.
Oh by the way, some care should be taken when selecting your replacement
options for your aging and obsolete rear suspension system. Remember that
the most expensive, complicated, and labor intensive to install design is
not necessarily the best performing or safest alternative available.
Sully
77 Royale
On Tue, May 1, 2012 at 8:16 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
>
> bryant374 wrote on Mon, 30 April 2012 15:50
> > I am in the process of replacing the body/frame isolator pads. Thanks
> to those that did this before me and provided instructions that were very
> helpful. All new pads are in place but I am having a problem with the rear
> isolator body supports. I have at least a 1/4" gap to fill. Got the nuts
> off the large bolts but having difficulty in removing the top rubber
> isolator (donut) from the bolt, allowing me to put washers on the bolt to
> take up the gap. Was going to put washers under the 4 bolts in the aluminum
> plate but those bolts are too short and stuck in that plate also.
> >
> > Suggestions on what you did appreciated.
> > Thanks,
> > Bill
>
> Bill, I'm trying to get to the very basics of this. I'm wondering why the
> rear mounts are so far from seating. It seems on the surface that you have
> raised the body back up to where it needs to be. If you have that much
> clearnce to the rear mount, either the new pads are overly thick or the
> body has sagged in the middle. One thought is to pull the rear back down
> beyond where it wants to be right now.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
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> Unsubscribe or Change List Options:
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: Body/frame isolator pads [message #168272 is a reply to message #168221] |
Wed, 02 May 2012 11:06 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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[
[/quote]
Bill, I'm trying to get to the very basics of this. I'm wondering why the rear mounts are so far from seating. It seems on the surface that you have raised the body back up to where it needs to be. If you have that much clearnce to the rear mount, either the new pads are overly thick or the body has sagged in the middle. One thought is to pull the rear back down beyond where it wants to be right now.[/quote]
If he went from the long thin rubber strips to 1/2" pads a 1/4" gap on the rear donuts sounds about right. I put in the thick pads and had more then 1/2" space at the rear donuts(way too much). I didn't have a problem with the front donuts however. I think the only way to correct this gap is too add a spacer block or a stack of flat washers. I wouldn't want too try too just pull in the gap and cause damage as the body should be resting on the donuts.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Body/frame isolator pads [message #168290 is a reply to message #168272] |
Wed, 02 May 2012 16:38 |
Jim Bounds
Messages: 842
Registered: January 2004
Karma: 0
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Senior Member |
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So it looks like my deep dark secret is out, wondered who would spill the beans, too bad it was you Sully. Figured it would have been someone else.
Now that you know I had tried everything and actually landed on something from another application, yes, I (actually a retired engineer friend who has a GMC) helped us figure out how to faithfully cut a 3x1" hockey puck down the middle to create what I have to tell you guys is the best body pad you could have.
How could that be you ask-- OK, think about this-- the purpose of the multiple body pad design is actually 2 fold:
1. faithfully hold the 1/2" gap needed between the frame and body to route your brake, air, LP and fuel lines without danger of crushing them. Of anything, I feel this is THE most important feature of the body pads we provide. Most of you will find your body pads crushed or missing leaving all of those important lines either crushed, damaged or in danger of being so.
2. The multiple pad arrangement effectively "decouples" the body from the frame. It's not as much the softness or derometer of the rubber that is important, you could come close to doing the same thing with a block of oak, the important thing is the contact patch of the body to the frame is reduced. This less that total footprine helps to reduce the amount of vibration from the transmitted from the frame to the body and that is what is important about reducing road noise and vibration.
You will never crush a hockey puck!!! and if you glue it in well with something like Gorilla glue, chances of them ever falling out is minimal. The original body pads were one sided "peal and stick". No wonder they slid out! I seriously believe that first having a front to back body pad, the derometer of the soft rubber they used was fine but some bright engineer thought of the less contact area theory and when they cut the full length pad into seperate squares essentially reducing the footprint between the body and frame they forgot that now the pad made of the same derometer rubber would now crush down. Douuuuuuuuu!!!!!
You cannot have too small of a gap between the body and frame just as you cannot go much over 1/2" or things start to not fit. Truth be told, you can install a 1/2" thick hockey puck without even loosening the outrigger plates! Yea, it will squeeze right in with a well placed bottle jack. We do it here bout every day, certainly every week. Bottom line here is using 10 hockey pucks cut down the middle you get 20 body pads. Cost for this is much less ($50) than the previous "kit" and everyone we have put these in for have been delighted most actually saying they can feel the difference.
So there it is, I came up with this application for a different part, what is that worth. It's kinda like coming up with the perfect stainless steel rear panel screw, yea it was another industry from another application but isn't that called thinking out of the box, isn;t that called creativity and isn;t that something to seek? You guys can debate this til the cows come home, I know this works, it's less money and to my thinking works great and will be there for years. Copy me if you want but my bet is you will not be able to cut 10 hockey pucks really nice for less than $50. Hey, look at that, why not break down and support the GMC dealer network, we are really working hard for you. I'm saving you big money, the least you can do is thank me by buying this from me. So that's my "commercial message"-- resistence is futile!!
If you have any questions, call me
Jim Bounds
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| Re: Body/frame isolator pads [message #168297 is a reply to message #168068] |
Wed, 02 May 2012 17:36 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I would think the process of cutting a hockey puck in half could present quite a few accident scenarios with grabs and throws, kickback and fingers. Perhaps best to leave this to Jim B who has allready figgured out a safe (as far as we know) way of doing this.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Body/frame isolator pads [message #168299 is a reply to message #168227] |
Wed, 02 May 2012 17:44 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""Bob, the reason that a 1/4" needs to be added to the very rear (as well as
very front) body mounts is that the original body bushings (except the
front and rear two) were 1/4" thick pads placed between the chassis frame
and the coach floor framing""
Got it, but I always thought the original pads were 3/8 thick not a quarter. Also, I think the front and rear donuts sag and compress permanently. I shimmed my front ones to relieve the aircleaner to hatch interference and reduce the chipmunk bow on the sides.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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