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Rear Suspension Upgrade

By: Dave Karp(DGE479)

 

Rear suspension installation and tips for cars with rear isolators. My car was starting to squat on one side and I decided it was time for springs. I like the car a lot and didnít want to go the cheap route (I donít feel suspension or brakes are a good place to skimp). Our Magnums were blessed with good handling for their size & time but over the years, time & miles do take their toll. I went a little overboard and replace every thing I could find new (NOS when possible).

Parts List:
Set of 5 leaf H.D. springs (just suspension) aftermarket


Set of 4 U-Bolts. Donít be cheap. Get new ones and the nuts, as theyíre still available from Mopar.


Set of 4 urethane isolator bushing (OEM was rubber, discontinued long ago, got them from Just Suspension)


Set of isolator clamps. Mine were beat and I was lucky to find them new (Just Suspension). These hold the Isolator bushings. Just Suspension didnít have many left.


Set of E body Polyurethane Shackles. They are the same dimensions as the Magnumís and are REAL AWESOME. They allow a lot more spring travel and are used by Mopar Action Magazines lap of America Valiant.


New shocks. I used Monroeís as KYBs are too firm for the NJ roads.


Sway bar links and bushings (if you can find them). I could not find end links and had to drive 80 miles to get the rest of the stuff from some dealer in NY State.
 
Removal:
 
1) Place car on safety stands so the suspension hangs free and put a hydraulic jack under the center of the rear, and raise axle enough to take weight off springs. You may now disconnect the rear shock abs at the shock plate or remove them for replacement; this is a good time to do so.

2) Disconnect sway bar end links (If you canít get new bushings for this, no reason to remove it).

3) Lower the axle to allow springs to hang free. Keep the jack under the center of the axle and just touching.

4) Loosen & remove u-bolts, DO NOT TOSS THEM YET, if they arenít available a leaf spring company can make them, you will need the old ones for this. I did get them from a local dealer.

5) Remove spring plates and isolator clamp with bushings

6) Make sure you SUPPORT THE AXLE, It is heavy and will hurt you!

7) Loosen the nuts from the front hanger and remove three on each spring but leave one loose. LUBE THEM GOOD, the hanger is not available. Now loosen and remove the rear shackle. The rear of the spring can be lowered. Now take out the front bolt that is loosened and take out the spring.

8) Remove the hanger from the spring; do not worry about the front eye bushing, as your new springs SHOULD have it installed already. You will probably need an impact gun on the thru bolt.  NOTE IF YOU LET THE AXLE DROP, BYE-BYE BRAKE LINE!!!!!!!!!
 
Installation:
 
1) Take your new spring and install the front hanger (do not tighten it fully yet)

2) Put the front hanger thru its holes and install nuts to 35 foot-pounds.

3) Assemble the rear shackles and install to the manufacturers specs if using polyurethane, again to not tighten all the way yet. Donít forget to lube these urethane bushings or they will creak loudly. If you use OEM type shackles or repro w/rubber bushings all is same but do not lube rubber bushings.

4) Position the upper isolator bushing and the spring/shock abs plate over the locating pin on both sides and place the new U bolts through the holes. If you are using the new urethane isolators: a) not necessary to lube. b) Have them in a 70F-80F degree environment so they will be flexible.

5) Put the lower isolator bushing in the clamp and put it up and thru the U-bolt studs then install the nuts. Tighten this to 45 ft pounds. If you use OEM bolts they are tough to turn, this is ok as these are "stakedĒ so they cant back out.

6) Install new shock and sway bar end link. Do not tighten yet.

7) Put drums and tires back on, Tighten lugs to 85 ft pounds (yes I really do this) and lower car to ground.

8) Tighten front pivot bolt to 125 ft-pounds (do your best, kind of tight here), shackle nuts to 45 ft pounds for stock (READ the instructions for aftermarket), and the shock absorber nuts to 35 ft-pounds. Tighten sway bar link end now too.

9) Measure the front ride height, as it may have changed (when the rear goes up the front goes down). Take for a test drive. You should do a front-end alignment

You should now be rewarded with a nice firm ride and be able to have friends ride in the backseat without bottoming out Enjoy!!!!
 
 
Notes:
 
On this job I removed the wheels and drums even though the service manual says nothing about it as a step. It makes it easier to maneuver the axle with the extra weight removed. Not to mention safer.

Try to have a helper with you, so if you get hurt someone is there, plus this stuff is not light and the positions are awkward.

If you use the urethane parts, they will need patience and finessing, but it is worth it. Do not try to draw parts together with the bolts. It will cost you.

I highly recommend a Factory service manual. Iíve seen them at swap meets as low as $5.00 used $40 new. Well worth it.
 
Note that the Isolator clamp is deeper on 5 leaf cars than 6 leaf cars if you want to upgrade, these clamps are hard to get. My parts sources, and lots of tech advice from:

My local Dodge dealer. I am blessed with a local dealer full of MOPAR nuts. they got me the U bolts and located a lot of hard to find bushings and sway bar brackets, My car did not come with a rear bar, even though it has HD suspension.


Just Suspension, 1-800-872-1548 owner Bill Kanouse. This guy has a lot of Mopar stuff at reasonable prices. He supplied the urethane Isolators, Isolator clamps, Heavy-duty leaf springs, and Polyurethane shackle kit. He is also getting me a new HUGE front sway bar that fits same as original. He even has a few of our torsion bars. ONE OTHER THING, this guy realizes that cars were made after 1974 and said he is hoping to help service these cars. He may look into reproducing the Isolator clamps and possibly torsion bars. He has been calling Mopar Performance to get a status as they list them but donít actually have them. These bars are just about all gone!!! One way to get other vendors going is for them to hear there is a market. A lot of these guys know each other.
 

 

 

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