'65 Formula S rear springs

-
Bob Jasinski

Bob Jasinski

FABO Gold Member
FABO Gold Member
Joined
Mar 7, 2019
Messages
530
Reaction score
273
Location
Danville CA
So I have my "original" rear springs off my '65 Barracuda Formula S. The part numbers on both are 2403804. They are in very good shape and I will be reusing them with new rubber bushings. However, when I check the number in the '65 parts book, it shows Barracuda, Heavy Duty as 2495086. The "originals", 2403804, are 6 leaf per F/S spec, and fit and looked just fine when installed. When I search 2403804 on FABO, I come up with posts indicating these are for a '66 Barracuda Formula S. I am curious if anyone knows if there is a difference between the '66 and '65 Formula S springs. I suppose it is possible these were replaced at some point, but they are original Chrysler springs, not aftermarket, and can't imagine why they would have been changed out, unless it was a warranty exchange maybe. Any thoughts on how/why the '66 springs would have a different part number than the '65 F/S?
 
My 65 Formula S came factory with 6 leaf springs, HD shocks, and front sway bar. 65'
 
Yes, that was the FS spec, along with the tach, thicker torsion bars, 14" wheels and a few other items. I'm wondering what the difference was in the '65 vs. '66 Formula S rear springs, if any.
 
IIRC the stamped number on leafs is not the same as the p/n. Might be the difference between the main leaf and the spring pack or some other reason. It may have been discussed on moparts - sorry I just don't remember. We do see this with some other parts such as brake master cylinders.
 
Both years used a HD 6 leaf spring pack, so, I doubt there is any significant difference. If the car doesn't sag in the back, just use them. If it does sag, get some new ones from General Spring.
 
I'll be removing my '65 Formula S leaf springs next week for a rebuild. Where exactly will I find the number you all are discussing? Thank you.
 
Did the '66 and '65 Formula S have different rear spring rates? If so, that would explain the different part numbers, and I'd like to know if the '66 is heavier than the '65 or vice versa. Both are six leaf.
 
Here are the springs. I believe them to be original to the car, but the part number is '66. Small point I know, but I'm trying to stay true to the original car.

DSC_2996.JPG
DSC_2995.JPG
 
According to 440source.com (see quote below), both part numbers mentioned in post #1 made their debut in 1964. They may have been used in any number of model years after that date.

"Now on to the numbers themselves: Chrysler's part numbers are date specific, and if the numbers are broken down, it is possible to determine the year that the part was first put into use. Note that the number only tells you the FIRST year it was used. If the part continued to be used for five years, the number will not indicate this. The numbers will almost always be a 7 digit number. For clarity and ease of writing, this seven digit number is usually broken up into two parts, a prefix and a suffix, similar to a seven digit phone number. However, the way it is split up is with the beginning 4 digits first (the prefix) and then the last three digits (the suffix) which is a mirror image of how a phone number is divided.

A typical part number might be a cylinder head: 2843904. The first digit represents the decade. A "2" in this case is the 1960's. Part numbers starting with a "1" would be from the fifties. The second number represents the year. So in this case "8" would be 1968. This is why most big block parts will never start with a prefix earlier than 17 or 18, as they were first designed and released in late 1957 for the 1958 model year. This date system holds true for almost all part and casting numbers up until about 1969.

During 1970 for some reason (except for a few 30XX parts) the 30XX-33XX prefix numbers were skipped and part numbers started at about 34XX, so most numbers for 1970 and 71 will begin with 34 or 35. An example would be part number for a 1971 440 4 barrel intake manifold: 3512 502. The 36XX prefix started in late 1971 and was used through most of 1972. 37XX started in late 1972 and was used through most of 1973 and 1974. 38XX started in late 1974 and was used mostly in 1975. 39XX was very limited and used in 1975, and then the numbers rolled over to 4000 prefix. One famous part that began to be used in late 1975 is the 4006 452 heads. Numbers seemed to stay in the 40XX and on a more limited basis, the 41XX prefix through all of 1976-77-78 to the end of production."
 
For the most part, that seems to be true, but, not always. Take the '68 340 intake for instance. It starts out 25XXXXX, but, wasn't until 3 years later that it was available.
 
cudamark said:
Take the '68 340 intake for instance. It starts out 25XXXXX, but, wasn't until 3 years later that it was available.
Click to expand...

I believe the number beginning with 25... is the casting number on the intake manifold, not the number it parts book. In fact, I have a '68 340 manifold right here with me: casting #2531915
 
That makes sense, the part numbers and casting numbers are often just one number different. Makes one wonder how long ago the 340 version was imagined by Chrysler engineering.
 
Yup, the cylinder heads also have a 25XXXXX part number in the parts book. I always wondered if they developed the intake and heads for the D-Dart and just didn't use them on that project, but, later decided they would work nicely on a bigger small block.
 
I really wish one of us knew a Chrysler engineer that could answer questions like that for us. It's like asking how the pyramids were built, nobody knows for sure.
 
I just installed some V-100 (6 leaf) springs from General, in my 65 Barracuda, not a formula "S" but it will be finished off with a "very" frisky /6.
Norm

General V-100 springs.jpg
 
I agree. I'd have a bunch of "what the hell were you thinking" questions for them!:soapbox: Like why didn't you just use B-body brakes and wheel pattern on the A-body? Why have several bell housing patterns so each transmission is different? Why didn't you make the strut rods easily removeable like Ford or the later Mopars? Etc, etc.....
 
Maybe there is a difference between Automatic transmission and manual? I doubt it. Or they ran out of 65 springs and on to 66. More likely.
 
Thanks all, for your feedback, and Dibbons especially for the insightful coverage of Chrysler part number progression. I am of the belief that my FS was born with these springs, and they shall return to their rightful place under the car. I should be getting the body back next month all shiny and new, and the rear axle will be the first thing to be installed.
 
I saw those too, on eBay, but the originals are 5" x 1-1/4" and four are required for the spring pair, not six. Having said that, they do look right otherwise. The seller states they are 2-1/2" x 1-1/4",but then you would need two per clamp and there would be a splice...doesn't make sense.
 
Here's a shot of an unbroken original. 5" x 1-1/4" . 1" between the "lips". Found something similar for Ford products but dims aren't shown so I emailed them.

DSC_3002.JPG
 
You must log in or register to reply here.
-

Back
Top