My new old Jet Age 300

This is the right leaf spring. It is VERY different visually than the left one. To my eye, it's looks damaged or collapsed.

20210605_102436.jpg
 
Last edited:
It does look funky.
They need to be replaced regardless. Weather they have 20 thousand or 200 thousand at 50 years old they and the rest of your suspension need to be replaced.
 
cretin90 said:
This is a great forum,and all of you guys are very helpful. Thanks to all of you!
So I bounce tested the car. It's ridiculous:..I can push the entire rear end down about an inch with no force. If I rock it up and down, tbe car bounces (I'm not kidding) at least 6 inches. I feel prettt stupid, because I just assumed you know , old car..that's how they were......ooof.

I think the KYB's seem the best option .
Thanks again!
Click to expand...

If the car will bounce 6", the air shocks have probably raised the rear end up enough to take most of the tension off the rear springs. This is not a good thing as now most of the rear vehicle weight is now on the frame cross member which is not designed for that purpose. Left that way the cross member will fail at some future date.

Dave
 
Last edited:
cretin90 said:
This is right leaf spring. It is VERY different visually than the right one. To my eye, it's looks damaged or collapsed.

View attachment 464597
Click to expand...

Looks like the top leaf is broken under the pad mount for the rear end. You might also want to remove the clamps on that side and check the condition of the center bolt. A broken center bolt will cause the leaves to shift and not align properly. Most of the time if a center bolt has failed, the car will not track straight. Check the wheel base on both sides to see if they are both the same. (Center hub front to center hub rear) Most 440 equipped 300's had a 7 leaf spring set, not 6.

Dave
 
Last edited:
We replaced the springs on our 68 300 vert in late 2018 with new ones from ESPO. When I looked a them the other day, I noticed they looked more like cretin90's right-side spring than the left side. I remember even when they were first installed, they were pretty much flat with almost no arch at all. They were "stock ride height" so my understanding was that was normal. But now they look wavy. Does that mean they are going bad? If yes, could something have been done wrong when they were installed? (They were installed by a local garage). Ride height still seems ok, however.
 
CBODY67 said:
But it also takes good HD shocks to resist compression of the springs and resultant bottoming-out. Not to forget about some "good judgement" of when you might be driving too fast for road conditions, by observation, which is what "brakes" are for.

As for the "quick lean on the fender" method I mentioned, every Chrysler product I've been around since the 1966 models has not given more than about 1.5" of downward deflection from my then-165lb body weight. Similar GM cars did more, police-spec vehicles did less.

NOW, it does not take a rock-hard spring rate to achieve this, either. I learned of a "brake-tap" action that can help, too, especially coming out of a quick dip. With some practice and good HD shocks, things can be more level than "exciting".

Remember, too, that as strong as the Chrysler UniBody might be, it will still "give" from suspension inputs. Which means that certain parts of the structure are designed to absorb/deal with these things, as other areas are not. Which means that whenever you take flex out of the suspension pivot areas with harder poly bushings, you then transfer these forces into other areas that were not really designed to deal with them. Which can lead to sheet metal cracks and similar, depending upon whether the car is a hardtop, sedan, or convertible as to just when and where these things happen, by observation. As in the allegedly typical B-body convertible cracks on the rh Dutchman panel/rh upper quarter panel joint.

All rubber suspension bushings are not created equal. Some are harder than others, by observation, especially at the GM OEM level. As the normal aftermarket replacements are usually harder than the GM OEM items were, by observation. From what I've determined, the OEM Chrysler items were harder to start with.

Now, poly bushings have their place in pivot-only locations (as in upper control arm, rear spring shackles, link-bolt sway bar ends, and other sway bar mounts which don't absorb road forces) as rubber bushings (which are hopefully of a harder durometer rating than stock) should be in road force absorption areas (lower control arm bushSome ings, leaf spring front eye bushings). Some might not agree with my hybrid approach, but after seeing the coach joint cracks develop on my '77 Camaro with the F41 and WS-7 upgraded suspension, over time, there's more flex in a unibody than many might suspect. And the GM versions of "unibody" need sub-frame connectors for their best durability, especially on T-top cars.

Just my respectful observations,
CBODY67
Click to expand...
This is the kind of analysis I like. Thank you, sir.

so , what i've gathered is that for my car (two-door coupe with the 383), I need the standard 6-leaf springs with standard ride height, KYB shocks, and rubber leaf bushings , and poly bushings elsewhere. I'm also assuming new U-bolts. Can you recommend a brand for springs and bolts?


I called a shop in Simi that specializes in vintage cars, and they were cool with me bringing in my own parts. I could probably do this myself since it's largely bolt together stuff, but I want this done in a day, and I only have hand tools so far.
 
Davea Lux said:
Looks like the top leaf is broken under the pad mount for the rear end. You might also want to remove the clamps on that side and check the condition of the center bolt. A broken center bolt will cause the leaves to shift and not align properly. Most of the time if a center bolt has failed, the car will not track straight. Check the wheel base on both sides to see if they are both the same. (Center hub front to center hub rear) Most 440 equipped 300's had a 7 leaf spring set, not 6.

Dave
Click to expand...
Hi Dave-
hey, what's the result of using (440) 7-leaf springs on a (383) 6-leaf?.....I ask because I'm having a hell of a time finding these springs for less than $450 (EACH!!) ..I see the 440 sizes for less than half that. Would my car's *** be bouncing all over the road? Sorry to be such a newb, I just don't know enough yet about these old cars.
 
You won't notice much difference, the 440 got the heavier springs to help control rear axle wrap-up on hard acceleration. Ride quality is about the same.

Dave
 
Strate-
Thank you...yes, I feel quite lucky as the new caretaker. I never thought I'd own a car with a vinyl top...and a white one at that.
 
You must log in or register to reply here.

Similar threads

Pete Kaczmarski
Hagerty article, Imperial ambitions in the age of Exner and Eisenhower
Replies
9
Views
3K
LeBaron1973
LeBaron1973
C
The Story
2
Replies
20
Views
3K
65sporty
65sporty
Turboomni
1969 Dodge, and the changes that should not have been made
Replies
15
Views
4K
fury fan
fury fan
Dga26
  • Locked
For Sale 1970 fury vert tx9 white top buckets console
6 7 8
Replies
151
Views
41K
68Furymb
68Furymb
MOVE N UP
1000 mile 21 hour road trip to acquire my 1968 300
2
Replies
22
Views
2K
live4theking
live4theking
Back
Top