Body Bushings

[mattsmonte]

Hi guys.

I have been reading a bunch of posts here for a while. This is my first post.

Reading the site I know all of the OEM part numbers for Regal, Cutlass, & Monte Carlo. One post here said that the Grand Prix was the tightest for body mounts. Does anyone have a full set of OEM part numbers for the 7 positions, upper and lower for the Grand Prix?

Thanks

Larry

 

[mattsmonte]

I would be interested in years around 87.

 

[mattsmonte]

Tt

 

[UNGN]

I don't know about the Grand Prix bushings because mine has all poly, now, but the stiffest lower bushing is the pink 457915 and the following would be cosidered a "full set" of factory bushings:

Pos 1- 348080 upper 2ea
Pos 2- 330986 upper 2ea, lower 457915 2ea
Pos 3- 348080 upper 2ea, lower 457941 2ea (457915 will work for lower)
Pos 4- 348080 upper 2ea, lower 457917 2ea (457915 will work for lower)
Pos 4- spacer 6262234 2ea, washer 337559 2ea (Replace Spacer and Washer with 457915 Lower)
Pos 5- 556755 upper 2ea
Pos 6- 330942 upper 2ea, lower 377801 2ea (457915 will work for lower)
Pos 7- 1242754 upper 2ea, 457915 lower 2ea


The bushing positions are numbered 1 thru 7 running from the front of the car to the rear.
Position descriptions:
#1 Radiator core support, upper wshr #337559
#2 Firewall, upper & lower
#3 Mid cab, upper & lower
#4 Rear cab, upper & lower w/spacer & wshr
#5 Over axle, upper
#6 Trunk front, upper & lower
#7 Trunk rear, upper & lower

 

[bmackinnon]

Which one is the 'usually missing' one? and is this the same as the 'gnx' bushing??? Thanks! :smile:

 

[UNGN]

Which one is the 'usually missing' one? and is this the same as the 'gnx' bushing??? Thanks! :smile:

#5 is the "missing" GNX bushing.

Replacing the lower washers with actual bushings is where most of the stiffness gains will come from.

 

[bmackinnon]

#5 is the "missing" GNX bushing.

Replacing the lower washers with actual bushings is where most of the stiffness gains will come from.

Thank you sir!! and thank you also for that excellent parts catalog you are kind enough to offer!! :smile:

 

[mattsmonte]

Thanks for the post. Big help to get the GP numbers. Big help in understanding the 457915. I am not sure if the #1 is for upper or lower. For the Monte Carlo the 348080 is the lower and the 1255795 is for the upper.

 

[Hot Air]

Don't waste your $'s on stock rubber bushings. Purchase a full set of poly bushings...you can get them in black so no one is the wiser!
Conrad

 

[UNGN]

Don't waste your $'s on stock rubber bushings. Purchase a full set of poly bushings...you can get them in black so no one is the wiser!
Conrad

The only problem with going with a full set of poly bushings is though it stiffens the car a lot, it can make the interior a little rattlely because of the transmitted vibrations.

If you have under dash/interior rattles now, you will REALLY have them after going to a full poly set up. If you are going to open road race the car, I'm right there with you going to a full poly set up... but...

just replacing the missing lowers will provide an improvement you can feel for about 30 minutes worth of work (If your car isn't from the rust belt).

 

[bmackinnon]

The only problem with going with a full set of poly bushings is though it stiffens the car a lot, it can make the interior a little rattlely because of the transmitted vibrations.

If you have under dash/interior rattles now, you will REALLY have them after going to a full poly set up. If you are going to open road race the car, I'm right there with you going to a full poly set up... but...

just replacing the missing lowers will provide an improvement you can feel for about 30 minutes worth of work (If your car isn't from the rust belt).

that's what I was going to say.... as if these cars need to be made MORE rattley... (as if that was a word)!!

 

[Hot Air]

I live in the middle of North Carolina (near Charlotte) so the roads are ok. I have never really noticed any difference in the vibration...it is just not a problem with my GN and it is a T-Top car. Guess I'm just lucky. I would for sure inspect all the body bushings for condition....if they are hard and crumbling or missing, I would go with new bushings...rubber or poly...your choice. Poly may be cheaper.

FWIW, I'm 61 years old and like a good ride.

Conrad

 

[karolko]

in my opinion, if you are going to be doing serious modifications to you car, i.e. frame notch, tons of power, launching off a t-brake, then rubber bushings should only be used.

Obviously, when you use poly bushings, being so stiff you are incorporating the car's body into the frame, thus the tighter and stiffer ride, and if you are aiming into turning your car into a handler, then this might just be your direct option.

Please do not let anyone convince you to by a set of poly bushings just becasue they are 3 times cheaper!!!

i went out and spent the moeny to purchase the factory GM rubber bushings, but i am modifying my car heavily, so i want all the "play" that rubber bushings have in order to help isolate my body from the frame so it doesn't buckle.

 

[turbofish38]

The only problem with going with a full set of poly bushings is though it stiffens the car a lot, it can make the interior a little rattlely because of the transmitted vibrations.

+3
Pick up a brand new OEM bushing and compare it to a poly bushing. They are both pretty hard as far as I'm concerned.

The big thing you have remember is that the polys are a permanent mod. Great for all out racing but who here drives their car like that on the roads? Kind of like buying a 4WD truck just for the few times in a year that you need it. They do absolutely nothing as far as handling is concerned. Aint nobody ever done a scientific test saying they picked up anything but a sore back from installing polys. Me Included.

There was a reason why Buick left out those lower bushings and Chevy didn't. That should lead you on the path to body mount enlightenment.

 

[mattsmonte]

Good stuff on this posting.

One reason I am looking for the Grand Prix numbers is that certain OEM bushings are no longer available. For the 87/88 Monte Carlo the #1 Core position upper 1255795 is gone. The lower 348080 is available. The uppers and lowers from 86 and before are available (14034780 and 457941), but they are softer. I was hoping to find both of the position #1 numbers for the Grand Prix since they are a little harder.

UNGN gave the number for what I think is the lowers. Anyone have the uppers for the GP?

 

[83hurstguy]

FWIW, my car was a rattletrap, after I put on the polys it actually quieted down... there is a lot less flex in everything. I could even heard the doors creak slightly on bumps/curbs before... silent now.

One of the best mods you can ever do to a G-body.

 

[UNGN]

FWIW, my car was a rattletrap, after I put on the polys it actually quieted down... there is a lot less flex in everything. I could even heard the doors creak slightly on bumps/curbs before... silent now.

One of the best mods you can ever do to a G-body.

This is true that door and T-top flex will be much less, so the noises associated with those will be much less with poly bushings.

The noises that will increase will be dash rattles and panel rattles and that type of noise. Things like the glovebox door can buzz, where they were quiet before, because nothing was vibrating them at a high enough frequency.

 

[mattsmonte]

Well, it has been a while, but here is the result of my research and what I plan to do:

Many G bodies had bushings left out. Some that are left out (position 5) make the rider softer. I would think that leaving out lowers and only using washers would make the rider a little harder.

I have a MC. Not all of the bushings are available. As I understand it, the Grand Prix bushings were the genearlly stiffer than the MC. They are as follows:

position-----Upper----lower
--2---------330986----457915
--3---------348080----457941
--4---------348080----457917
--5---------556755----none
--6---------330942----377801
--7---------1242754---457915

I could not find all of the MC bushings. In position 1 I could not find the 1255795. It is very similar to 457915. However, 457915 is a little harder and more shallow on the first inside shoulder. I know some other people are going with 377801, which is shorter and a little softer than 457915. I think that going with a harder substance that fits tightly with 348080 may make the responsiveness of the cornering a bit better. I also put stiffer mounts on position 7. Staying away from delrin might protect my A-pillars. I have a t-tops.

I could not find MC uppers for positions 1, 2, 5, 6, and 7. The lowers from softer to harder are: 457941, 377801, 457915. I have been told that 457915 will work for position 1 upper and all lowers 2-7.

Where I could not get MC parts, I went with the Grand Prix parts. In some of the positions, I stiffened the lower part a bit since I have a little more HP and wanted it a bit firmer ride. Since GM had a pattern of having positions 3 and 6 lowers a bit softer, and since I had the parts, I went a little softer there.

Here are my choices:

position----upper----lower
---1-------457915----348080
---2-------330986----457915
---3-------330951----377801
---4-------330951----457915
---5-------556755----none
---6-------348080----377801
---7------1242754----457915

I believe all the parts I chose are all still available. GMpartsdirect.com, oepartsource.com, discountpartshub.com are all potential sources. I would note that you will quickly find Dixie's price a decent one IF you have to order in ones and twos and pay shipping from each source. Try and bunch up your order as much as possible.

Hope this helps.

 

[Brian Mc]

I have energy suspension polys in my hardtop Monte SS, and in the suspension, but I also have an 88 Corvette so I probably have a higher tolerance for rattles:redface: :frown: but I like the feel of it a lot. I wouldn't consider it harsh at all, and it has 17's. Maybe it's my KYB GR2s softening things up.

 

[mattsmonte]

When I said that I would think that leaving out lowers and only using washers would make the rider a little harder, I did not understand how the set up worked. Here are two links that show that GM left the bolts hanging when they left out bushings. Leaving out lower bushings actually makes the ride softer.

THE HERD: Enhanced Body Mounts

Also a recent thread on there about bushings.

Body bushings - Impala SS Forum

As far as the delrin approach for positions 1 and 7--check out postings by MAP on this site.