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Changed to poly body mounts

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By Design Poly restricts movement better than rubber which causes the bushing to move in its housing..... a bushing is not supposed to move in its housing. The problem is not the bushing binding.... the real problem is why does it bind.


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If the bushing moves in a truck, why wouldn't it in a car application? Almost no suspension bushing I can think of sees up/down or side to side only motion. Every suspension bushing I can think of sees a lateral load as well as the "intended" range of movement.

Examples? 2wd front control arm bushings. Driving straight, pretty much straight up and down travel as you hit bumps. Turn the wheel though, and they are dealing with up and down, AND the lateral load of the turning tire. Rear leaf or coil spring suspensions are the same way, one side up, one side down, the bushings are seeing a lateral load, and if poly binds, (instead of giving like rubber) you are limiting travel by increasing the amount of force it requires to move the suspension, AND making the movement less predictable.

I think if poly were actually so good for suspension, you'd see it in OEM applications more, such as the Camaros, Mustangs, and Vettes, but AFAIK, you don't.

Anyway, theres nothing wrong with disagreeing, and just so we are clear, no hard feelings here. I hate seeing these type of things degenerate into a flame war.
 
Poly being bad and rubber being good or vice versa is purely subjectional. Alot depends on the use and "desired" results. If you desire the most flex out of your suspension, then rubber is the way to go, and as Dorian stated, good OEM rubber will last quite a while. Severe duty usage may require poly (but then again poly is not indestructable either). I chose to run poly bushings in all my locations (especially suspension) due to what I use it for (truck pulling where deflection is highly NOT desired). I use it on the street too so I did not want solid bushings (i.e. brass lined or solid aluminum), but I don't want the amount of deflection that rubber offers, so I went poly and won't look back. If I were building a trail rig, I would probably go with good rubber bushings if I was looking for flex and reliability (rubber seems to be much more "forgiving" than certain grades of poly). As far as body mounts go, if your frame is ultra twisty, you may want the deflection of good rubber (at the expense of longevity) to keep from ripping the body apart at the mounts or causing gaps to close up and hit, but if your frame is pretty stout (such as most fullsize rigs) then poly seems to be the better choice for longevity and sag reduction.
 
Dorian, No hard feelings here..

Look at that control arm bushing you are talking about.
There are three major parts to it the outer case, the poly bushing itself, and the inner metal sleeve. The arm is located to the frame via a shaft bolted o the frame this shaft fits in the inner sleeve of the bushing assembly( thats where the rotation is supposed to occur) The bushing isn't supposed to limit rotational motion around this mount, its is supposed to limit the lateral movements of the arm during is travel. If you look at the double wishbone suspension design you will see that the upper and lower arms have different travel paths, allowing caster and camber to change through out the travel of suspension. these different rates of change impart different forces(sizes and directions) at the bushingsand ball joints. The suspension is designed to have so much caster and camber change through out suspension travel. the softer the bushing the more the suspension reacts differently than designed, The harder the bushing the more accrate the suspension is( but you usually get a harder ride).

The reason that the factory still uses rubber bushings? That's easy cost, longevity and comfort. they cost less and they last longer and are more compliant.
 
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The reason that the factory still uses rubber bushings? That's easy cost, longevity and comfort. they cost less and they last longer and are more compliant.

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Well, that kinda gets back to camber/caster and so on. If the poly did that in an acceptable way, don't you think something such as a Corvette would use them? I know the application/necessity, but since poly doesn't allow travel smoothly, it affects handling...it may do it differently than rubber (bind vs. deflection) but it still affects handling. To be honest, thats what it probably comes down to: Neither of them is "ideal", both are a compromise, and have their own quirks that need dealt with.

Second...price OEM bushings against poly, and you'll see that poly is usually MUCH cheaper. I did the K5 for $100, I'd bet GM would be $200 easy. (and thats "at cost") Check out Camaro 1LE rubber bushings, they are something like $20 EACH, with 4 per rear axle. (upper/lower rear control arms)

Third, by all accounts, poly should last longer. Less affected by oil, etc., which means it shouldn't break down as quick. Of course, the automakers don't care about the product after the warranty period expires, so why go overboard?
 
I prefer rubber bushings myself, for all the reasons stated. Good rubber bushings work very well, and I hate squeeky poly. That said, I've run poly in my last couple of trucks simply due to cost and availability. It wasn't worth the effort to seek out and pay for the rubber. &lt;shrug&gt;

Just to throw in one more thing, is there any source of rubber bushings other than OEM? I hate buying from the dealer, the price is nuts. Someone said LMC caries them, but that won't be much better. Any others?
 
You know, Moog carries a line of car bushings called "Sanaprene", maybe they have truck apps too? It's a harder durometer rubber, so it's more oriented towards the "performance" side of things.

Even if Moog doesn't make Sanaprene for trucks, perhaps they have "stock replacement" truck bushings.
 
OK guys, I come again in this discussion to clear a few points.
All the detail talking about suspension bushings is referring to arms and links, and in those designs at least to a point the geometry is close to correct so the motion is just axial so if you use rubber or poly or even aluminum it works.
Now move to leaf springs, when you have anxle that is twisting one side drooping and one side stuffed, what do you think is happening at the bushings in the eye of he spring?
It's not just turning around the bolt but it's trying to twist or the spring has to twist to follow the line of the axle. This is where rubber is more forgiving and poly usually falls appart and cracks, and if you followed Steve's thread for a while about ORD greasable shackles and poly bushing problems you would know what I am talking about.
Now a new developement today, I was visiting a pipe factory, and they were showing the procedure where they make the joints, and they were using this yellow liquid they pour in a steel form and cure in 130 degree F for 15 minutes and it comes out a rather soft polyurethane piece.
Much softer than the poly in the market now. They showed me the testing on it up to 20,000 PSI with no damage, garanteed for more 20 years under the harshest conditions.
I asked IF they can provide me with a few gallons of this stuff so I can experiment some, luckily the guy was a car buff and he went on telling me about his 31 chevy he is restoring, so he said he will see what he can do, and he would be interested in what I come up with.
So I might be making some soft poly bushings soon.
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Poly is good for body mounts on a truck but not for truck suspensions. Poly is also good for every aspect of a sportscar where there is less suspension travel than a truck. With less suspension travel you eleminate the binding that occurs when these bushings are put in a truck. As far as this suspension guru I think I will stick to the recomendations of Rad Rods, E.T. Shop, numerouse NHRA Pro Stock builders, ........
 
Look what I wrote. I was referring to leaf sprung suspensions (as that is what mine is). I also stated that for my particular use (unlike 99.9% of the people on here), poly suspension mounts are better for my pulling truck. I did state that for off-roading, or flex, I would go with rubber (or a compound like you are investigating). As with life, there is no end-all solution to ALL problems/situations. Diligent research is needed to determine needs, possible solutions, drawbacks to each solution, weigh the pro's and con's (as well as experiment) and then choose what works (or in most cases, what you can afford, and can afford to live with). I think most of us are seeing eye to eye (we are just different heights /forums/images/graemlins/smile.gif)
 
Ouch! Just found some of those after market bushings. $15 for each piece, takes 2 pieces for each eye they say. That's $180 in bushings for just my front springs! /forums/images/graemlins/eek.gif However, the counter person I spoke too didn't instill a great deal of confidence in her knowledge for a variety of reasons. Now, IIRC, the rubber style bushings are one piece per mounting location, not 2 piece like poly. Is that not correct? It has been many years since I actually tried to get out a set of OEM bushings, and I don't remember for sure. Maybe I'm confusing them with my hot rod "A" arm bushing replacements? Can anyone give me a clue???
 
What?
go online at 4wparts.com they have the whole set for the front springs for I think $40. I got mine cheaper 10%discount.
 
I should have been more specific. I was talking about after market, OEM spec, rubber bushings. Just like the factory rubber bushings, but after market.

The price your talking about, is that for the soft bushings that Dorian was talking about? Or regular poly? Also, is that all 6 positions (front and rear springs, plus the ones in the frame)?
 
I haven't replaced my stock ones yet, based on known difficulty on getting them out/replacing them, and replacement costs I haven't researched yet.

I really think that they are one piece though, which is why they are so hard to remove. Maybe you should talk to NAPA. From most accounts, their employees tend to be more likely to actually know what they are doing than others. Have you checked lmctruck yet?
 
Napa said they do not carry MOOG bushings and they can only supply poly. The price (and the info I posted that I think is wrong) I got was from a local spring shop.
 
Check this out:
http://www.carparts.com/parts/sample.asp?reflink=39323-0-0-0-0&amp;SegmentId=1&amp;parttypeid=27018&amp;vehicleid=39323&amp;catalogid=&amp;partnum=NONE&amp;dc=

If you can't get there, it's under 1986 K10, then "springs".

SB320Leaf Spring Bushings, Front Suspension; Bushing $15

SB335 Leaf Spring Bushings, Rear Suspension; Shackle Bushing $10

Not sure if that means the upper/lower on each spring end are different, or what. Anyone thats replaced theirs should know what quantity of each you would need.

You are looking at $120 for the front and $80 for the rear. Not cheap. Then again, if they last like OEM, easy 20 years off of a $200 investment. I've got the 85/86 parts manual at home, if you want me too, I can look up the GM number, maybe we could get lucky and they are still available, and cheaper than aftermarket.
 
Have the box right here...

Energy Suspension 3.4118G "GM 4wd body mount set applications include 81-91 K5/Suburban"
 
Well, can't find the general listing, but the part number look up worked. I may go that route later. But money is tight right now so, I'll probably just go with poly to get my new main leafs in. If (big if) I can get the poly's out of my current main leaf (they are prety much new) then I only need the frame side of the shackle. I'll mark these parts for future reference...
 
Well, heres what I can find, and the illustration does NOT show these, or quantity required:

3887751 Bushing, Front Spring Eye, K1,2,3
468481 Bushing, rear spring CK1,2,3 RR SPR RR Eye (3"O.L.x1.5"THK)
350544 bushing, RR SPR FRT CK2,3
363913 bushing, FRT SPR SHKL K1,2,3

Can't find in the manual what this one location means, but on that last part #, there is a number "4" in its own column. Almost like how many is required, but I can't be certain.

Most of them are in the $10 range, but that last part number is a whopping $1.58 from www.gmpartsdirect.com For that price someone should order it and see what the heck it is! The only bushing even shown is that front spring shackle bushing, and it *looks* like they are two piece bushings. Pack Qty on GMpartsdirect is 2 for $1.58, so that *might* mean $3.16 per side for the shackle bushings.
 
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