Steps to remove a “C” body sub-frame the way I did.
This worked for me; use your own judgment as to if it is something you want to try. I make no guarantees as to every Mopar “C” body will be this easy or will fit when you are done so be careful and don’t damage yourself or your car.
1. Remove the windshield wiper arms and the cowl piece. To do this, remove the lower windshield chrome trim, this is held on by screws inside at the top of doorpost, near the bottom of windshield. The rest of the chrome is held on by snaps. After the chrome is off, a few more screws and the cowl can be taken off.
2. Remove the front bumper at the frame, four bolts, an impact wrench helps here.
3. Remove the grill, lots of little screws etc shop manual helps here. The cross piece that the hood latch is on can come off too.
4. Remove the front-end wire harness.
5. Drain the cooling system and remove radiator, battery and tray and windshield washer bottle. Don’t break the bottle – they are expensive!
6. Remove the outer fender liners. A lot of bolts are located along the fender and in the middle of the wheel well. The worst bolt is by the battery tray, that one is always corroded. It will probably break but repair with a standard nut is not a problem. The undercoating can be a problem too.
7. Open both the front doors and then put something to protect the front edge of them when you remove the fenders. Rugs would probably work good or heavy cloth. There are two studs on the bottom of each fender, one stud inside the door just below the windshield, and there are a number of bolts along the edge of the hood. There are two or three down the radiator support and one stud at the bottom of the radiator support.
I did this all alone but a helper with the fenders would be a good idea.
8. Remove the radiator support as it is just sitting there now anyway.
9. Remove the inner fender liners; a few bolts on the frame are all that are left.
10. You now have to remove the exhaust pipe somewhere below the engine. I had a 318 with a crossover pipe and I took all the exhaust off behind the crossover pipe. While you are under there, the fuel line has a rubber hose at the rear of the cross member you can take off and plug the line to keep fuel from dripping.
11. Drop the rear u-joint and remove the drive shaft. Plug the automatic transmission and be careful not to nick the input slider area of the front tube that goes in there. I drained the transmission fluid before I started because I was going to change it anyway and it made it less messy. The speedometer cable has to be removed too. Remove the throttle linkage also.
12. You should now be ready to jack and measure. Four good jack stands are a plus. If you use blocking, be sure to have it all the same height. Measurements need to be made without the car moving from the time you remove one sub frame and replace it with the new one.
First I raised the rear of the car just about five inches and set the rear jack stands so the car would be level and just high enough to squeeze under it when I raised the front. I jacked the front of the body and motor up with a floor jack under the cross member the motor mounts on. Then I used jack stands to support the front of the car so the front tires were off the ground just about an inch. Make sure the front supports are under the rocker panels where you see four spot welds just outside the rear cross member/transmission mount. I used a 2X4 chunk to protect the rocker panels and if you were to look inside that area of the rocker panel you would see there is reinforcement for the body at those four spot welds. If you have done this right, your front tires should only be a little ways off the floor (about 3/4") and the car level or very near level.
Once the car is level and solid, I let the floor jack down from under the front cross member and the front frame will drop about a half an inch - scared the heck out of me but the weight of the motor without the fenders makes the whole thing pretty flexible. Now with the front hanging out in space, mark some semi-permanent points on the floor under the 1/2" holes near where the bumper mounts are on each side of the frame. These are alignment points and are in the same place on every stub frame. Measure how far from the hole that it is to the floor with the weight of the engine on the sub frame. Record that distance someplace as you will need it when you put the new frame under the car. With everything back like it is now, the distance on the new frame should be the same. Now you can put the jack back under the sub frame cross member and take a little of the weight off the whole assembly.
13. Remove the four front attachment bolts which are at the leading edge of the firewall on the “U” shaped bracket sticking out from the frame. (If you do have a second jack, it might be a good idea to put it under the rear cross member before you start taking out a lot of bolts. Loosen and remove the four bolts that are in the rear cross member under the car. There are still two bolts under the carpet and hidden behind a plastic plug. These bolts are very special and have a cone alignment shoulder, try not to damage them use lots of oil or whatever! The nut is under the car the bolt head is inside the car. You will have to remove the kick panels and fold the carpet back to find the large plastic plugs. These are the rear alignment bolts. They position the sub frame from side to side and front to back. These will be the first bolts you put back in when you are putting it back together. One hole in the body is a slot with about a 1/2" side-to-side slop and the other is round. When you go to put the sub frame back in, the round one goes in first! Loosen those two bolts but don't take them out yet or the frame will drop! You should take one of them out and then replace it (snug) with a longer (5 inch is what I used) bolt and some large washers on top. Then remove the other side and replace that with a long bolt and washer. Now with the whole thing hanging and loose in the back and on the jack in the front, lower the front jack till the wheels are solid on the floor the loose rear top bolts will act like a hinge.
Take the jack out from under the front and go back to the rear. Put the jack under the rear cross member and remove the long bolts that it was hanging from. Lower the rear and roll it out. There are shim packs on each side on the front-firewall attaching point. Keep track of these, I had to add a new one to my new sub frame on the drivers side and removed one on the passenger side.
When you go to replace the new frame, you will need to roll the new frame under the car and jack the back up enough to get the long bolts back in. Once the long bolts are in, tighten the slotted side up sort of snug with the long bolt don’t force anything. Now go back to the front cross member and raise the weight off the wheels till the frame is close to where it should be, leave room for the shims under the firewall mount point. Then remove the long bolt on the round hole side in the floor and put the proper shoulder bolt back in, you may have to jack a little to get it in. Once that bolt is tight - watch the special washer on the bottom of the shoulder bolt, it has to go over the tapered shoulder so the nut and flat washer are solid against it. Now the other side can be replaced with the shoulder bolt and brought almost tight.
Adjustment time! With the two floor bolts near tight and the front on the jack, try to put the shims under the firewall and tighten up the four bolts that hold it there. You should jack the front up till the shims are tight before you tighten the bolts, don’t try to raise the weight of the motor and frame with the bolts. Once they are tight, let the weight on the jack down and measure to your points. It should be within a 1/16 of an inch or less. You will have to change shims on the firewall till it is, this it the hardest part but if you want your fenders and hood to fit, you have to do it. Don’t use washers for shims. If you don’t have enough, make some out of sheet steel.
Once everything looks like it did before you removed the old one, put the four rear cross member bolts in and tighten them, tighten the floor bolts and check measurements again after all ten bolts in the body are tight.
Now you can reverse all the removals and you are back in business. One thing, I put the jack under the front cross member when I put the fenders and wheel liners on to adjust the droop. Once you have the fenders back on and tight, you can take the car off the jack stands. The car is not supposed to be supported by the rocker panels when you jack it so you have to compensate by taking off the weight on the front during re-assembly.