Hello,

I am in the process of pulling the body off the frame of my 72 SS and have been told that "while I have it off" replace the body bushings. However, I have been getting the debate from both sides of the fence.

1) only use Urethane bushings will help with performance
2) Use Rubber because Urethane help a little but make the ride very rough.

Just a little background : My 72 SS is almost ready to go to the paint and body phase. the suspension is more or less done, shocks, springs, global west ( del-a lum) front and rear adjustable. Soooo, because I am in the process of trying to hit all of the areas with new parts. I would like to at least replace the body bushings but, i'm really stuck on which way to go. I want a car that has good performance and handling but not something that rides really rough.

has anyone installed one or the other? good or bad stories ??

any help is appreciated

thank you.

I do not think it is an issue of riding rough. I think the issue is more of a noise issue. The rubber provides some noise isolation between the frame and body whereas poly does not. So with poly you will here more clunks and thunks as the suspension works and hits road irregularities. You will also hear more normal road vibrations as they use the body as a huge speaker.

Whether all this is ok or a major annoyance depends on your own taste. It has taken a long time since I converted the top strut mounts from rubber to solid in my Mustang to get used to the extra sounds. It bothered me quite a bit initiallly so I personally would not recommend changing away from rubber.

I did poly, i did it alone and my ride definitly tighted up quite a bit. all my interior was in for about two weeks, now it is all stripped out and the hwole car rattles like crazy because it is in the process of body work/paint. It was really quiet and not rattley when i had the interior in but i can't say for sure if it is more rattly. All of my bushings are poly though in the car but i like the feel of my car and it not being to mushy. I did replace 35 year old bushings though so maybe new rubbers would have been better.

Also poly was only $65 when rubbers were like $90 if i remember right. Anyway good luck.

I used Poly everywhere and I have no noticable squeaks or excessive road noise.

I have poly in my Elky and would recommend the same for you. I don't have any noise that wasn't there before and I think it helps the car feel tight.

Ryan

If you look at original body bushings you will see that they are flattened out and cracked like all the ones I have seen. The rubber takes some of the stress of the body panels by giving it more cushion. Car bodies are made to flex, and I believe the rubber works better to relieve stress in the panels.
If you look at a frame without the body, its riding on springs and shocks to cushion it, and the frame also flexes, so if you take the flexibility out of any part of it you have changed the compatibility of the whole structure.
Frames are a lot thicker then body panels, yet they made them to flex. I could have explained this a little better, but you guys know what I'm trying to say.
My father would keep a pickup truck for a long time, and he would never have to buy a battery, I would ask him when he put the last battery in his truck when I worked on it, and he said He never had to.
Getting to the point here.
He would baby his pickup truck, super slow over bumps, you could say he never ever stressed that truck out. I believe yet to this day thats why his batteries seemed to last forever. His batteries never got a pounding of much up and down, so no plate separation or settlement disturbed.
Stop and think what is bolted onto that body that could be effected by making it more rigid. Window mechanisms, light filiments etc.
Yeah I agree probably doesn't really make a difference, but why stress out anything that you don't have to.
Rob

Flex is bad. Poly will help tie the body and frame together to reduce the flex.

Poly body bushings here, but rubber suspension bushings, motor mounts, and trans mount.
I ran a poly trans mount with the th350 for about 10 minutes, pulled right back in the driveway and took it off, it was unbearable. I used to use one on my camaro with a manual though and it was much more tolerable.

Poly body bushings here. Big improvement in overall perceived "stiffness" of the car and it didn't make any difference in noise. Actually it got quieter because the body (namely the windows) don't creak and flex as much anymore. I also deviated from the factory setup; my car (and the shop manual) shows the factory body mounts with just a top donut under the rocker panels (no lower donut or bolt in that location). However, I noticed the body has a cage nut provision at that location; so I bought two spare lower poly donuts and added the bolts and lower donuts there. That helped a bit, too. Don't know why the factory doesn't use a lower donut and a bolt in that location on coupes (it only shows a lower donut and a bolt under the rocker panels on wagons, elkys, and convertibles.)

I'm planning to machine my own aluminum body bushings a bit shorter than the factory pieces-- I'm hoping to lower the body over the frame another 1/4" or so and tie things together even more rigidly; it looks like there's clearance everywhere to allow the body to sit a bit lower over the frame, so why not?

Also, I run poly motor mounts and a rubber trans mount (same as Brian, bad experience with a poly trans mount.) I'm going to try a set of solid motor mounts soon and see how that goes.

Troy

What is the problem with poly engine and trans mounts? I've got a set of brand-new ones sitting on my toolbox waiting to go in. :clonk:

What is the problem with poly engine and trans mounts? I've got a set of brand-new ones sitting on my toolbox waiting to go in. :clonk:

the poly trans mount just greatly amplifies the slightest engine/driveline vibration and sends it directly into the cabin of the vehicle.
Unless you have a habit of breaking trans mounts (it happens on drag cars sometimes), I would just go with a stock rubber mount.

I have solid mounts that I made from 6/6 Nylon Rod.

I also deviated from the factory setup; my car (and the shop manual) shows the factory body mounts with just a top donut under the rocker panels (no lower donut or bolt in that location). However, I noticed the body has a cage nut provision at that location; so I bought two spare lower poly donuts and added the bolts and lower donuts there.

I also added a mount at this location. It seems to be the perfect place to add some regidity to the chassis. I can not comment to the noise or quality change to the ride with the solid mounts. My car is very unfinished inside, so it is loud already.

As for the engine mounts and trans mount, I used to run solid mounts on the engine of my stock car, and we ran a rubber mount on the trans. This gave the assembly a little flex in case of accident (common in our class). And I would agree with Brian that it would likely add to any driveline vibration that you might have.

Good Luck.

Thank you everyone for your comments.

the poly trans mount just greatly amplifies the slightest engine/driveline vibration and sends it directly into the cabin of the vehicle.
Unless you have a habit of breaking trans mounts (it happens on drag cars sometimes), I would just go with a stock rubber mount.

Exactly. The poly motor mounts are quite nice (they're interlocking so they cannot seperate, they're stiff enough to keep the engine from torquing over but compliant enough to take a little vibration out) but the poly trans mount added a LOT of driveline vibration to my car, even with a properly set pinion/driveshaft operating angle. All the problems went away when I changed back to a rubber trans mount.

Troy

Don't forget that if you run poly's you will need the sleeves from the rubber one in order to install the poly's since they don't come with the sleeves.
As for the difference between rubber and poly. I'd go with Rubber.
I installed poly on my 68 years ago and yes it did indeed stiffen the ride and I didn't notice any squeeks and I thought it was cool for about a week or two.BUT. That car was a dialy driver and I noticed that the car reacted to every contour of the road in a jerky fashion. It was as if the car had hydraulics and someone was toggling all the switches at random. In otherwords the car felt neurotic. Don't get me wrong it was awesome on a track surface or a smoooooth road, but real world roads in So. Cal. drove me nuts,and I was only 23 at the time. After a couple of weeks I put the Rubber back in. Now replacing old rubber with new will make a dramatic difference in your car as well with out the drawbacks that can be associated with poly.
I currently have allot of the Pro-Tour goodies and run Del-A-lum,Spherical bearings, and poly front control arm bushings, but still run rubber body mounts. Just my .02 cents worth

Over the years, we have replace transmission tail extensions becaused they were cracked. Not many but, usually the customer used a poly transmission mount. You need to have some flex in the driveline. This is not my opinion but real world facts we see occasionally.

I was shaking my 69 SS down this fall, after frame-off resto, noticed alot of drive line noise. All angles in drive line were good. Running TH400 with gearvendors OD. I have poly motor & trans mount on. I'm in the process of removing the trans mount and put back to rubber. I stayed with rubber body mounts.

The Urethane Bushings are good to have but yes they are hard i have a stiff ride when i first took my chevelle out on the road for the first time but after i got it running i drove it for 2 months straight and i drove it hard i turned corners at 7-11 mph i braked hard and i took speedbumps and bumps in the road hard which in turn loosened up all my suspension bushings which now its not as hard it fills real good and the car has little and i mean little flex in corners it fills like im driving a car with a wide track suspension set up on it or something.

I to am in the process of replacing my body bushings and am contemplating the same thing, rubber or poly?

I think I am going to go rubber, just because I want a bit of a comfortable ride. My wnts and needs of my 69 are changing as time goes, and I now am after a nice cruiser. I am just in the mindset that poly won't give me the ride I am after.

What I would like to see is someone do a back to back test, new rubber bushings then new poly bushings then back to new rubber bushings. I really wonder the overall diffrence. I haven't done it yet, but expect an incredible diffrence in handeling after replacing my 37 year old rubber bushings with new rubber bushings. How much better would the handeling be by replacing my bushings with poly?

Jeff

I changed my rubber to poly last year, you do feel and hear more of the road but personaly I like the feel of the car now.

Craig