Leaf spring differences for 68 C-bodies and maybe other years. Soft to Firm.

[wyrmrider]

Great find on that book I'd seen one at the dealer where i was parts then service manager
I owned 59.65 66 Imperial 69 Polara and 73 New yorkers, one with factory trailer tow
I added a leaf to all of them and had a wide variety of samples to choose from when building a new stack using only the main leaf. I like the plastic interliner it comes in a roll and is full width and cut to length
it has fins up and down on each side, slides real nice I spray the leaves with zinc dichromate paint then moly spray'
on the C bodies I install the rear sway from a Cordoba it is a bolt in
and use the 74-78 1" plus torsion bars PC or SW if you can find them PC wheels for a stock or 8" wide
radial tires do not like narrow rims hd quick ratio firm feel box if you can find one or build one
I also built a late 73? B Body ish fury 3 seat station wagon really big torsion bars for these 400 car
Had a 62 Fury 2 door wagon 3 speed 318 poly but had all the matching year 413 parts and a torque tube 4 speed car got stolen, would have made a great show car still have the long rear impossible to find side glass if anyone needs and maybe a spare windshield

 

[kmccabe56]

That’s what I am hoping to draw out from the crowd.
I do know my Polara D-L w 383 engine would have had the 3004 658, but the pn on the bottom spring is 2835 354. Mine has 5-1/2 leafs. So at some time the part number was super seceded.

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Not necessarily. The part number you find in the parts catalogue is the SERVICE part number. The part number that is stamped on the spring itself is the PRODUCTION part number, either for the entire leaf spring assembly, or for the individual spring itself. Service part numbers and Production part numbers are RARELY the same. Do you recall GM advertising "Computer Selected Springs"? Well, Chrysler to a certain extent did the same thing. Springs varied based on what optional equipment is built into a car. I recently saw a sheet on a car that looked like the window sticker, but it had notations with the individual options of how much they added to the weight of the car. Not sure where or why sheets like this would be printed out, but there are engineering books that list all this information.

IF you're looking to make a reasonable improvement in the ride/handling of your car, go to the torsion bars and leaf springs that are specified for a 440 equipped car. They will be
larger/beefier than those for a 318 car. Chrysler engineered the cars to ride level, in most cases, with just a driver on board. If you want your car to ride level with all seats occupied and the trunk full, consider air shocks and a height control valve. '78 NYBs among others had a vacuum powered pump that could add air to the rear shocks when called for by the height control valve. There are aftermarket kits that can do all of this, with a small electric compressor.

 

[Boydsdodge]

I just as well post the remaining pages.
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Great find on the book, I love old factory tech books and films.

 

[HWYCRZR]

I got the notice that my ESPO springs should ship today and arrive mid next week. So maybe install them next weekend

 

[HWYCRZR]

Received and installed one of my rear leaf springs. They shipped out at the same time, but one missed the truck transfer and should be here tomorrow. I ordered the 6 leaf pack, std was the 5-1-2 for my car. I figured the 7 leaf would be stiffer than I was used to. Anyway the arch of the old and new was about the same, but when you compress them you can definitely tell the originals are not as stiff. So does re-arching always work? On mine unless they gave them an aggressive crown, I am not sure if they would have been stiff enough.
So as I was taking my original off, I decided to borrow the half leaf with the assembly # and install it on the new pack. So now I have 6-1/2 leaves.
Took about an hour for the one side including adding the 1/2 leaf. The lift with the trolley jack is a life saver.
Am waiting for my new rear shocks which should also come tomorrow. Right now the left side sits about 1-3/4” higher than the right side with the original. And yes I made sure all the weight was on the springs and jounced it a number of times before tightening and torquing the bolts.

 

[HWYCRZR]

Installed one other spring and new KYB Gas Adjust shocks. I took it for a quick 20 mile shakedown from bumpy county roads to the interstate with about 3/4 tank of gas. Can really feel the difference in the ride. Not so much harsh, but firmer. Handled the bumps and corners much better. It seems that the rear sits about 1-1/2 - 2” higher. Next step fill the tank all the way up, check the ride height of the front, check alignment ( maybe changed the caster with higher rear). And the re-adjust my headlights.