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Iso pads installation [message #342394]

Tue, 09 April 2019 05:24

tgeiger

Messages: 518
Registered: February 2006
Location: kansas city

Karma: -1

Senior Member

Whoo boy, finally getting the iso pads put in. Ended up just cutting the carriage bolts out, hope to find a replacement bolt that may be stainless steel or zinc. Will need to loosen the donut bolts at the front and back of coach. Hoping I will not need to replace them. Will do the jack stands and lower air bag pressure on one side at a time to lessen the frame uplift pressure. I saw the # 10 Tek SS screws being used. Would 3/4" length be enough or should I do 1" length?

Thanks,
Tom
76 Eleganza 2
KCMO

Tom Geiger 76 Eleganza II KCMO

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Re: Iso pads installation [message #342395 is a reply to message #342394]

Tue, 09 April 2019 06:44

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

WOW! I have done 4 coaches and never even loosened the bolts. Those things are bedded in the wooden floor and some times over compress intothe wood if too tight. I am thinking the floor is 1" or 3/4" thick plus you have the thickness of the bracket, plus the thickness of the aluminum shield on later coaches, and the thickness of the nut. I have a problem and I am thinking that 1" might be too short. I can not see where anything less than 1" would work and maybe they are even longer than 1".

All of this is just an opinion from someone that has never even had one loose or out. I would get longer than need because longer will not hurt you while too short ones sure would.

If you have one of the old cutoff ones just measure it. Also look in the parts catalog. Sometimes they state by size what size bolt is used.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: Iso pads installation [message #342396 is a reply to message #342394]

Tue, 09 April 2019 07:39

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Glad to hear you are unloading the suspension and loosening all the hold-down bolts.

Here is a link to my experience. I have a 1977 and was going from thin (there was a variety of padding material or none in mine) to thick (about 5/8") pads.

http://www.gmcmhphotos.com/photos/g5800-isolation-pad-installation.html

Trick is to use several jacks along one side to lift one side of the coach evenly at once. The screws I used were self drilling, thread forming wide head machine bolts. I believe they are generally used for fastening roof trusses. These screws have Robertson square socket drives. Hard to find outside of Canada, but once you use them you'll toss your Philips, Torx etc screws in the garbage!

http://www.gmcmhphotos.com/photos/isolation-pad-installation/p39578-isolation-pad-replacement.html

To raise the 4 corner mounts because I went with thicker pads, I slipped several large flat washers under the donut to make up the space. The existing donuts were in good shape.

I used slotted washers at the front braces beside the engine to make up the height difference there.

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: Iso pads installation [message #342407 is a reply to message #342396]

Tue, 09 April 2019 19:32

Jp Benson

Messages: 649
Registered: October 2011
Location: Fla

Karma: 2

Senior Member

I recall that someone on GMCnet said one of their lower body panels made a cracking sound and has had a wavy texture ever since. Apparently that effect is not too common when installing new iso pads and not loosening the body/frame bolts. If you have a Ragusa step be aware that it is bolted to both the frame and the body. I added a rubber shim to the step mount to account for the increased height of new pads.

JP

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Re: Iso pads installation [message #342438 is a reply to message #342394]

Wed, 10 April 2019 18:00

tgeiger

Messages: 518
Registered: February 2006
Location: kansas city

Karma: -1

Senior Member

Yes, that is something I do not want to hear, cracking. I'm sure many have done this without loosening the hold down bolts but I'm going to loosen all holdowns that are on the coach just to make sure. I would like to replace the side rail hold down bolts with a u bolt if I can find the right one. May not, if so then I'll shop around for the best replacement bolts. I am doing the 5/8" pads.

Thanks all, looking forward to the nice ride improvement!
Tom

Tom Geiger 76 Eleganza II KCMO

[Updated on: Wed, 10 April 2019 18:01]

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