Rear Spring Swap
Not long after I got the '73 home, I noticed that the rear sat low. I checked the front end to make sure it wasn't set high. No such luck. My car had a droopy butt. I used photo tricks to minimize the condition when shooting the car. Examing the rear springs revealed the onset of a reverse curve in the back part of the spring on each rear corner.
The rear springs on the A-body are 55" long and are asymetrically attached to the axle with the longer part to the rear of the axle. The spring locates the axle and suspends the body. The leaf spring as installed by Mopar is a simple, primitive, yet effective device for its intended use.
Like others here at FABO, I looked around for alternatives for solving my car's condition. Some suggestions were to install a helper spring or air shocks. Either would cure the condition. However, on the basis of firsthand experience, I ruled them out. Both raise the rear spring rate making the car ride stiffer and promote increased understeer. With a /6 and 904, there isn't power to burn for kicking the tail out.
I shopped around for a set of springs that would give me a close to stock ride height and spring rate. Following the recommendation from either FABO or /6.org, I settled on a set from McVeigh springs. In the photo you can see a tired old spring next to a new one. Note the difference in the arc of the spring.
One of the negatives I've heard about swapping springs is that you have to remove the rear axle to do so. WRONG! By taking a systematic approach, the springs can be replaced without removing the axle or the tires.
Tools needed: Socket set, with breaker bar (and maybe a cheater bar); a can of rust penetrant, jack stand, tire iron or jack handle, jack.
Optional: Something to lay on while you're underneath the car. Also check your socket to see if it will fit over the axle clip nuts and still let you get a wrench head on it. If not you'll need a deep well socket. If you want to keep the shocks out of the way, you'll want a bungy cord or coat hanger.
This is a good time to inspect the axle clips. (That's Mopar parts manual speak for the U-bolts that clamp the axle, spring, and shock mount together.) If the ends of the bolts are bent, have damaged or badly rusted threads, there is a good chance they will be broken during removal. Have no fear. Although they are available from Mopar, at a premium, they are also at O'Reilly's ..etc. The big visual differences are the Mopar stuff looks exactly like what's coming off, less years of dust, rust, and abuse. The bolts I found in the HELP! section are gold irridite treated. Appearance didn't matter, so I went with the cheap stuff. They had them for 2.75 and 3.00 axle tubes.
Oh yeah. You'll definitely want the springs on hand. When you purchase, I suggest asking the vendor if past purchasers have needed to re-set the pinion angle with their installations. If so, you'll need wedges and tools necessary to set it. FWIW, mine did not need to be wedged.
Let the car cool down. Spray the rear shackle bolts, lower shock absorber bolts, clip nuts, and the bolt at the front of each of the springs with rust penetrant. Let it set over night so the penetrant can do its thing.
Pentrant spray areas shown below:
First thing to do is to remove the lower end of the shock absorber from its mount. Suggest using a coat hanger or bungee cord to move it out of the way.
Loosen this nut. It secures the bolt that holds the front of the spring to the body. If you can get it all the way off, fine.
Loosen the nuts on the spring shackle. If your shackles are installed like, these, go ahead and remove the end plates from the shackle.
Now is the time to break out the jack and jackstand. The goal is to lift the car to the point where the spring is fully extended (which is why the shock had to be disconnected), but the weight of the axle is being carried by the tire.
It should look something like this. Note the roundness of the tire. A radial, in particular, has a long foot print. It does not have to be exact.
Now comes the hard part, taking off the spring plate clip nuts. The factory ones on my Dart were long enough to require the use of a deep well socket. They all required my breaker bar, a 4 foot cheater bar, and a ton of patience. (I broke two of mine off too short to re-use.)
If you were able to get the end plate off of the rear shackle, you can wiggle the spring off the back at this point. If not, you'll have to remove the rear spring mount. There are four bolts that hold it in place. Pay attention to the way it comes off. The bolts are not in a square pattern.
The front mount is the same way. Remove all four bolts.
At this point the spring should be on the ground. Remove the front spring bolt and mount from the old spring. Install the front spring mount to the spring. If you're using an old spring, this might be a good time to replace the front bushing. I have yet to see a new spring that did not have a new front bushing.
However, I have seen springs that did not come with new rear bushings. And, I have seen shackles that did come with new rear bushings. All of the bushings I have seen have been two pieces per shackle bolt. The push into the spring eye from either side.
Reverse the process and you're done on one side.
There have been a couple of questions regarding the angle of the shackle.
Not long after I got the '73 home, I noticed that the rear sat low. I checked the front end to make sure it wasn't set high. No such luck. My car had a droopy butt. I used photo tricks to minimize the condition when shooting the car. Examing the rear springs revealed the onset of a reverse curve in the back part of the spring on each rear corner.
The rear springs on the A-body are 55" long and are asymetrically attached to the axle with the longer part to the rear of the axle. The spring locates the axle and suspends the body. The leaf spring as installed by Mopar is a simple, primitive, yet effective device for its intended use.
Like others here at FABO, I looked around for alternatives for solving my car's condition. Some suggestions were to install a helper spring or air shocks. Either would cure the condition. However, on the basis of firsthand experience, I ruled them out. Both raise the rear spring rate making the car ride stiffer and promote increased understeer. With a /6 and 904, there isn't power to burn for kicking the tail out.
I shopped around for a set of springs that would give me a close to stock ride height and spring rate. Following the recommendation from either FABO or /6.org, I settled on a set from McVeigh springs. In the photo you can see a tired old spring next to a new one. Note the difference in the arc of the spring.
One of the negatives I've heard about swapping springs is that you have to remove the rear axle to do so. WRONG! By taking a systematic approach, the springs can be replaced without removing the axle or the tires.
Tools needed: Socket set, with breaker bar (and maybe a cheater bar); a can of rust penetrant, jack stand, tire iron or jack handle, jack.
Optional: Something to lay on while you're underneath the car. Also check your socket to see if it will fit over the axle clip nuts and still let you get a wrench head on it. If not you'll need a deep well socket. If you want to keep the shocks out of the way, you'll want a bungy cord or coat hanger.
This is a good time to inspect the axle clips. (That's Mopar parts manual speak for the U-bolts that clamp the axle, spring, and shock mount together.) If the ends of the bolts are bent, have damaged or badly rusted threads, there is a good chance they will be broken during removal. Have no fear. Although they are available from Mopar, at a premium, they are also at O'Reilly's ..etc. The big visual differences are the Mopar stuff looks exactly like what's coming off, less years of dust, rust, and abuse. The bolts I found in the HELP! section are gold irridite treated. Appearance didn't matter, so I went with the cheap stuff. They had them for 2.75 and 3.00 axle tubes.
Oh yeah. You'll definitely want the springs on hand. When you purchase, I suggest asking the vendor if past purchasers have needed to re-set the pinion angle with their installations. If so, you'll need wedges and tools necessary to set it. FWIW, mine did not need to be wedged.
Let the car cool down. Spray the rear shackle bolts, lower shock absorber bolts, clip nuts, and the bolt at the front of each of the springs with rust penetrant. Let it set over night so the penetrant can do its thing.
Pentrant spray areas shown below:
First thing to do is to remove the lower end of the shock absorber from its mount. Suggest using a coat hanger or bungee cord to move it out of the way.
Loosen this nut. It secures the bolt that holds the front of the spring to the body. If you can get it all the way off, fine.
Loosen the nuts on the spring shackle. If your shackles are installed like, these, go ahead and remove the end plates from the shackle.
Now is the time to break out the jack and jackstand. The goal is to lift the car to the point where the spring is fully extended (which is why the shock had to be disconnected), but the weight of the axle is being carried by the tire.
It should look something like this. Note the roundness of the tire. A radial, in particular, has a long foot print. It does not have to be exact.
Now comes the hard part, taking off the spring plate clip nuts. The factory ones on my Dart were long enough to require the use of a deep well socket. They all required my breaker bar, a 4 foot cheater bar, and a ton of patience. (I broke two of mine off too short to re-use.)
If you were able to get the end plate off of the rear shackle, you can wiggle the spring off the back at this point. If not, you'll have to remove the rear spring mount. There are four bolts that hold it in place. Pay attention to the way it comes off. The bolts are not in a square pattern.
The front mount is the same way. Remove all four bolts.
At this point the spring should be on the ground. Remove the front spring bolt and mount from the old spring. Install the front spring mount to the spring. If you're using an old spring, this might be a good time to replace the front bushing. I have yet to see a new spring that did not have a new front bushing.
However, I have seen springs that did not come with new rear bushings. And, I have seen shackles that did come with new rear bushings. All of the bushings I have seen have been two pieces per shackle bolt. The push into the spring eye from either side.
Reverse the process and you're done on one side.
There have been a couple of questions regarding the angle of the shackle.
- This is a soft spring and it begins to deflect with any load put on it.
- Because Mopar used asymetrical springs, most of the spring deflection occurs towards the rear of the vehicle.
- I did the work in a parking lot and took the pictures afterwards. Consequently the trunk is full of tools and junk (lol). Without the load, it does sit a bit more vertical.
