gm 12 bolt swap/ upper rear control/trailing arms

[huntermetalfab]

we had modified stock control arms that worked fine but they tend to break so im thinking of building some new ones with heim joints on both ends. thinking that the movement of the heim joint will allow for the offset
what do yall think

 

[Lawfree]

we had modified stock control arms that worked fine but they tend to break so im thinking of building some new ones with heim joints on both ends. thinking that the movement of the heim joint will allow for the offset
what do yall think

Actually, many consider the G body 4 link stock set-up to be a "poor" design. With the upper and lower control arms being different lengths and set at different angles, it will bind up at it limits of travel. Using stiffer poly bushing only makes the binding issue worse. A 12 bolt swap will require either longer or adjustable upper control arms, and having a Heim joint on the chassis end will help with binding issue. Several companys offer adj upper control arms with Heim joints. With the car on it's wheels on a level surface you should shoot for @ a 2 degree nose down setting for your pinion angle. BTW, there are rubber seals avail from Speedway and others
to keep the Heim ends lubed.

 

[85 Cutlass Brougham]

Several companies offer suspension kits that keep the stock uppers and rubber bushings and then use spherical bearings on one of the bottom bushing positions to stop them from binding. Look at Global West, for example, as this is how they set theirs up. A friend of mine did a similar setup on a Fox Mustang and said you could get amazing articulation with the springs out. He got his from Maximum Motorsports

 

[tattoo72]

i looked into the 12 bolt swap, they are not a dirrect fit. the upper controll arm tabs welded to the housing are at slightly different angles than oem gbody. but i have known of peope using them with modifications to the trailing arms.

 

[joe_padavano]

Actually, many consider the G body 4 link stock set-up to be a "poor" design.

Considering that the same basic four link design has been used by GM and Ford for at least half a century, "poor" isn't the word I'd use. The whole point of the angled upper links is to provide lateral location of the rear axle without the need for a Panhard rod or Watt's linkage. Yes, the design requires some twist in the upper arms under some degrees of articulation. The stock rubber bushings provide enough compliance to provide this angular twist without breaking anything. "Upgrading" to poly bushings causes a problem. That's why the heim joints are needed at the front end of the upper arms in this situation.

Forcing an A-body axle into place with stock upper arms is asking for trouble. As noted, the angle of the tabs on the center section is wrong, which puts the forward end of the arms in the wrong place. Using heim joints in the upper arms is a bandaid at best, since it doesn't correct the angle problem. If you can use ball joints in the housing tabs, that does fix the problem.

 

[megaladon6]

i think they mean "poor" in that it's not good for handling. for generic ride quality and the like it's fine, but there are some definate (low) limits to what it'll do stock.

 

[bigdan]

went for straight 4 link ++ panhard rod
what a world of difference on handling ,never any binding issue ,
and so easy to adjust the uper armrs to get perfect pinon angle
the original g body ( most GM aniway) are compromise system
cheap to build and does the job most of the time ...unless your picky!
look at the original arms : sheet metal at best ,easy to bind & twist even with original power ......unless you upgrade the arms ,change set up !

Dan

 

[bowtie81]

i bought a set of control arms off ebay that are designed for a 12 bolt swap. the uppers have the proper angle for what it needs to be in a malibu.