What exactly do the body bushings do? - Chevy Impala SS Forum
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post #1 of 25 (permalink) Old 07-12-2004, 01:44 AM
NAESS
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I know that they are intended to isolate some road noise and bumps etc but with all the raving about what the stiffer ones do, I just can't get my head around why they would be such a huge improvement. As far as I can tell, they are not much more than glorified spacers.

Now with that being said, since firmer seems to be better, is there a limit to that statement? I'm assuming that aluminum would not provide the isolation needed but what about materiels such as hard plastic like HDPE?

Just a few questions so I can justify the mod.

NAESS
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post #2 of 25 (permalink) Old 07-12-2004, 05:44 AM
RJI
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Weak or soft bushings will allow the body to flex and allow more body roll and shift of weight. Firmer ones help control that. Too firm and you transfer way too much pounding and vibration into the car and stress to the body.
post #3 of 25 (permalink) Old 07-12-2004, 06:01 AM
Navy Lifer
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I'm sure you could turn up some info on a search, but this is worth discussing.

OEM "cabin comfort" criteria for any vehicle is a mix of many factors. Reality is, the Caprice was intended to have a fairly isolated passenger compartment, with as little intrusion of noise, vibration or harshness as the price point of the vehicle allowed to be spent on satisfying the requirements that ultimately come down to making the car acceptable to the customer base.

There is a big difference in a Caprice--a "family sedan" and a Corvette--a high performance sports car, for example, with different design and construction methods and criteria. Easy to see and understand.

The same is true to a lesser degree for a Caprice/Impala SS sedan and the 9C1 variant of the same vehicle. Spring & shock characteristics (stiffer or softer, valving design, different rate or load rating), tires (aspect ratio, tread design, recommended pressure), wheel size & width, and the body bushings (selected by rubber durometer, internal design--such as the number of voids-- length of spacers and lower cushion contact gap) are all selected/combined to meet specific performance parameters.

The differences appear to be quite subtle, and there are so many variables, it would be quite a task to become familiar enough with every different combination on any particular vehicle unless you worked (for GM) in the vehicle development area and had a good working knowledge of how the testing is done that determines each combination of factors. The OEM parts bin is full of parts the engineers and production people had to choose from when developing and building this car.

In the case of the Impala SS vs 9C1, it is easy to understand that the intended vehicle customer and use was distinctly different, enough so that the body mounting system got some special attention. Whether or not it was by accident or design, the Impala SS ended up with what most of us here on Forum seem to believe is an "inferior" combination of parts. Add to that the fact that we are now dealing with parts that have been in use for 8-10 years and in many cases are badly deteriorated. As enthusiasts, most of us will be of the mindset that we want the "best" on our cars, in whatever area (we) choose to focus, and the biggest factor is often whether the change is within financial reason. When we start modifying the car--engine mods, exhaust mods, changes to suspension, tire/wheel sizes and sidewall heights, powerful stereo systems, etc, we totally disrupt the OEM's tuning of the body mounting system as far as what will be felt in the driver's seat & passenger compartment.

So, it becomes a matter of whether the OEM has a good set of parts that can be identified as "best" or whether any aftermarket method may be superior--it will depend on what can be withstood in the driver's seat, and whether the specific use of the car will warrant the use of parts that impart a much more direct path for NVH "inputs" to the vehicle operator.

To answer your question, there IS a limit, but I really have no idea how a B-body would "behave" with hard plastic in place of the rubber mounts, but I do think you could notice the difference.

One thing to realize is that the factory parts may not always be available into the future, so if you have any notion that you want to maintain the OEM mounts as the vehicle ages, you should try to get your hands on those pieces now, even if you don't plan to install them for another 5 years.
 
post #4 of 25 (permalink) Old 07-12-2004, 08:48 AM
scot august
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Poly/Graphite seems to be the extreem point that works the best. Metal is a disaster. Rubber too soft. The Energy Suspension kit replaces all the upper and lower bushings,including the factory deleted ones only if you get part #ens-34136g, the other pn's either delet some or don't use graphite impregnated poly. The 34136g produces a tighter car that feels more rigid with a little more vibration and noise coming into the interier.No free lunch,but a much better result than just doing the lower body bushing mod.
post #5 of 25 (permalink) Old 07-12-2004, 09:41 AM
Dodger
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One word to the wise, something to consider anyway. Installing all 12 bushings is a time consiuming afair, not overly compledx, however more time consuming than you might first think. I got a little lazy and decided to have the shop put them in for me, thinking it was a quick and easy job, when I picked it up they said it took a little over 5 hrs to do, and this is at $69 hr, with the parts I spent nearly $400. If I had known this project was going to cost me this much, I wouln't have done it, I would have put the money towards something more important like gears/posi or headers. If you are mechanical do it, but if you have to pay the shop don't do it.
post #6 of 25 (permalink) Old 07-12-2004, 09:48 AM
Aaron D
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Lots of good info in this thread. Nothing groundbreaking but it is nice to see it all in one place...

The ES p/n 34136 is available from suspension.com for $98. I've done business with them before with good results. They're in CA. I believe it is a kit that only comes with body bushings and the price seems to reflect it.

The guy that runs the place seems like he is always 5 seconds away from turning into a cranky fart but never does so. His character comes through in the website as well. Its entertaining but I'd hate to see what would happen if I said the wrong thing.

Later,
Aaron

UPDATE: Summitt has the same kit for $81.39. Seems like a real good price even if you don't use all the bushings for the reasons Dodgercat specified. I think you would spend almost that much on the GM parts even at good guy prices if you only bought the deleted bushings. If you replace them all you will be money ahead.
post #7 of 25 (permalink) Old 07-12-2004, 10:14 AM
Sublvr72
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other than keeping the body on the frame?
post #8 of 25 (permalink) Old 07-12-2004, 10:32 AM
Rustic
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Quote:
UPDATE: Summitt has the same kit for $81.39. Seems like a real good price even if you don't use all the bushings for the reasons Dodgercat specified.
I would recommend buying them localy. The AutoZone here can get them for about the same price as summit and I'm sure there are other chains or local shops that carry Energy Suspensing parts.... that way you won't get hit with shipping.
post #9 of 25 (permalink) Old 07-12-2004, 10:58 AM
Aaron D
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Good idea Chris, I'll keep that in mind. I've pretty much given up on trying to get internet prices locally. If the price is the same it's usually a toss up between paying sales tax or shipping. Summitt has flat rate shipping, if I can afford it I usually wait for one large order and try to get it all done at once. I laughed when I got 4 15x8 wheels and a few small things shipped for $7.00.

Later,
Aaron
post #10 of 25 (permalink) Old 07-12-2004, 10:59 AM
Jim Spahr
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One note- the lower body bushings are fairly easy to replace. The upper body bushing are the ones that are difficult and time consuming. You can easily DIY on the lower bushings in the driveway. The upper bushings takes alot more effort and know how. The lower ones are the ones which are missing fromt he factory on most ISS's.
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