Questions regarding lower rear cab mount bushings for a 91 Chevy K1500 pickup

Hi everyone,
I purchased some new lower rear cab mount bushings or cushions for my 91 Chevy K1500 Pickup with a standard two door cab. The rubber bushings have what looks like a thin flat plastic ring bonded on one
end. On the other end, there is no plastic ring, but the outer edge of the bushing has a small fillet or radius.
What I need t know is, which end is up? Do I install the plastic ring against the frame bracket, or does it go against the round steel retainer / washer that is directly under the head of the cab mount bolts ?
Also, I would like to find some bushings that are tougher than the stock GM bushings. Does anyone know where I can purchase just two lower polyurethane bushings or is it always necessary to buy a whole bushing kit for $50.00 or $60 bucks ?
I would appreciate any feedback.
Thanks John
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Here's an option that might help if you've got another vehicle (or a friend that needs bushings) to offset the cost. McMaster-Carr sells polyurethane round stock. A chunk that's 3" OD X 6" long sells for 55 bucks. You could use a band saw it and slice it into discs of whatever thickness you desire. http://www.mcmaster.com/#8784k982/=1qygz4 They have a variety of stock sizes and durometer hardness specs to pick from, if you can stand the sticker shock. Good luck.
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Thanks Klutz,
I checked a drawing from the GM dealer computer and it does show the plastic ring being installed against the frame.
As far as the polyurethane, Mcmaster may be an option. I wish I could buy it in smaller or less expensive pieces.
Are there any other material options that would be of equal or better durability ? What hardness specs would be recommended for cab mounts ?
Before I installed them, I measured the new GM stock bushings with dial calipers in case I ever need to have two made custom. It's interesting that both the outside and inside diameter has a slight taper. Here are the stock dimensions of the GM bushing...
Outside diameter at the top side with the plastic ring = 3.098" Inch.
Outside diameter at the bottom of the bushing that mates with the round steel retainer under the cab mount bolt head = 3.042" inch
Inside Diameter at top side with flat plastic ring = 2.415" inch
Inside diameter at the bottom that mates with the retainer ring 2.36" inches
The total thickness or height including the bonded plastic end ring 1.091" inches.
The thickness of the plastic end ring is = .084" inches
Lower radius on the outer edge of the bushing = 0.138" inch
If I made two custom I would forget the plastic ring.
Perhaps if I put the word out someone will have some scrap or off-fall in such a small size.
Thanks again, John
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John2005 wrote:

You should be able to find ready made polyurethane body bushings for that truck.
http://www.suspensionconnection.com/cgi-bin/suscon/body_mounts.html http://energysuspensions.net/pages.php?pageid $
--
Steve W.

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Thanks for the links Steve, but I was never able to find a place where I could just purchase only the two bushings I needed. It seems they always make you buy a full kit for the whole truck for $50 to $70 bucks, instead of letting you buy the individual bushings you need for $8.00 bucks a piece or so.
John
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John2005 wrote:

That's because if you go poly you need to change them all.
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Hi Steve,
I can see where it would be ideal to change all of the bushings on the whole truck to polyurethane, but why would I *need* to change all of the bushings to polyurethane ?
Could I just use the two stock GM lower rubber front cab bushings and use two polyurethane mounts for the rear lower cab bushings ? What is the worst that will happen if I don't change all of the lower cab bushings to polyurethane ?
Do I need to change the upper mounts over to polyurethane as well ? I put new stock GM rear upper mounts on some time ago, but am not crazy about doing uppers again unless absolutely necessary.
I don't see why it would hurt to just put a couple of lower polyurethane bushings on the rear lower mounts. They will be stiffer and tougher, but what would it hurt ? It can't be worse than what I had before, which is no rear bushings whatsoever, the rear of the cab was sitting on the frame before I repaired the frame brackets and installed new GM upper and lower bushings.
Thanks John
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John2005 wrote:

Poly and the factory rubber have different durometer levels. The poly is stiffer than the rubber. If you only replace two of the bushings there can be a LOT of additional stress placed on the mounts when the frame twists and shifts. That stress can actually tear a mount loose. Sort of like one loose bolt can break other parts.
It's actually one of the benefits of Poly because you can tailor the durometer levels of the different parts to meet specifications. Take the sway bars, the stiffer the bushings the faster it responds. It is one of the primary reasons why you swap the suspension bushings to poly.
One drawback of poly is that some of it causes BAD squeaking, so you usually coat the bushings with graphite to stop that.
--
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Thanks for the additional info Steve,
Would I be OK just replacing the front and rear *lower* cab bushings to polyurethane, or would I need to also replace the upper cab bushings as well ? It's easy to change the lowers, but the uppers are a bigger job.
I never had any problem with the stock GM upper bushings wearing, they seem to be a tough combination of a steel piece with bonded rubber (very stiff). I only had trouble with the lower bushings wearing. Replacing every bushing on the truck would be a job, but just replacing the four lower cab mount bushings is no big deal.
John
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John2005 wrote:

Personally I would use the stock rubber if only doing one side. It may not cause problems but why take a chance of body/frame damage if you don't have to?
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