[Ramairnacho]

Today I learned that a formula and a ta had different leaf springs. What's the actual difference? If a formula got ra3 option did it get the ta leaf springs ? What about a formula with 15 inch rim option did it get ta leaf springs? Are front coil springs different too? Trying to learn more about these cars. Thanks

[Jack Ferris]

Here are a couple pics of some spring I have. First pic are the springs purchased from Pontiac many years ago as a 78 Trans Am application. Second is from a 70 Z28 I have in my shop. Pics don't show the spring rates but they appear to be the same spring.

[Jack Ferris]

This is off Firebird Centrals site

1970 - 1981 Firebird and Trans Am 4 Leaf Multi Leaf Springs Sold in a Pair, Premium Quality, Factory Height

New USA Made Firebird 4-leaf multi-leaf springs. Made off the original GM blue prints to give you the factory height. These 70 - 81 leaf springs are extra nice and have a tapered leaf and rolled edges with an anti-friction pad between each leaf to help provide a smooth ride. Rolled ends gradually decrease in thickness. The reduced thickness at the ends allow for increased flexibility of the leaf end, resulting in reduced stress and interleaf friction. Rolled ends produce the smoothest acting spring.







SPECS:
Correct 4 Leaf Set, 2-1/2" Wide, 126 Lbs., Rate, and 635 Load Lbs.

Fits all 70 - 81 Firebird and Trans Am models. Not a generic replacement spring, but the real deal. USA Made!

PART NUMBER: SUS-2685

[Ramairnacho]

There where 3 different leaf springs in 70. But what's difference and would a ram air 3 formula have ta suspension? The pic below is from Assembly manual.

[Jack Ferris]

Only thing I could imagine being different is differing spring rates. Maybe something that corresponded to the car having sway bars and/or sway bars with different diameters.
I don't know.

[jhein]

I don't know about factory specs for various models. I also don't know what springs were in my car when I got it. But, I had some ride height problems. Otherwise, the suspension was "stiff", so it cornered fairly well. But, when I got new Eaton Detroit springs on all 4 corners, KYB shocks and delrin bushings, it was like the whole suspension woke up. Much better ride quality, less harsh, faster acting and at least as good if not better cornering.

The Eaton website gives the same part numbers for 70 TA and Formula with 15 inch wheels. There is a different part number for the Formula with 14 inch wheels.

[RamAirBirds]

This also reminds of the fact that ORIGINAL springs for the 70+F-Body are different Left and Right. Replacements are same but if using originals L&R are different. Not sure it is Visually. It is more of a different spring rate for pass side...

[jhein]

Originally Posted by RamAirBirds

This also reminds of the fact that ORIGINAL springs for the 70+F-Body are different Left and Right. Replacements are same but if using originals L&R are different. Not sure it is Visually. It is more of a different spring rate for pass side...

Eaton has different part numbers for left and right leafs.

[Formulabruce]

If you opted for F-41 in 70 you got stiffer T/A springs and the 15 inch wheels/ tires . USUALLY, however the 15 could be ordered separately. This subject was beat bad last year, do a search. .
IMHO, after researching this I do not recommend Eaton 70-72 springs with different ratings per side.
The 73 model made both sides equal. This allowed for better handling tuning with the newer " crowned" roads AND radials. Hence RTS advertising shows up in 73.
Also if you buy new Eatons, select a lower rating than you think, or select a drop spring.

[unruhjonny]

THIS thread may be worth a read.

[Ramairnacho]

Originally Posted by Formulabruce

If you opted for F-41 in 70 you got stiffer T/A springs and the 15 inch wheels/ tires . USUALLY, however the 15 could be ordered separately. This subject was beat bad last year, do a search. .
IMHO, after researching this I do not recommend Eaton 70-72 springs with different ratings per side.
The 73 model made both sides equal. This allowed for better handling tuning with the newer " crowned" roads AND radials. Hence RTS advertising shows up in 73.
Also if you buy new Eatons, select a lower rating than you think, or select a drop spring.

My car came with 14 inch steel rims then i.got formula leaf springs. Can you school us on the stiffness? What's that mean?

[Formulabruce]

Originally Posted by Ramairnacho

My car came with 14 inch steel rims then i.got formula leaf springs. Can you school us on the stiffness? What's that mean?

Many folks forget that in most all GM V-8 cars ( not wagons, trucks or 6 cyl cars)
the tire height goal is 26 inches as they want just under 800 revs per mile.
This is true for new Vettes and 1970 Firebirds.
So, if you use 14" stock size tire, you get Same tire height as the 15, ( 26 inches) and Better Ride than the 15" as you have more sidewall to take the shock out of the road. This is a bit of a compromise on Handling though, but same fuel economy if width is the same.
Formula leaf springs are just a tiny bit higher rate, and the anti sway bar will help with roll just as the higher rate spring does. ( If the sway bar can move, many dont move much at all, either due to age and rubber, or someone cranked the mounts and drop link).
Eaton seems to have a problem with Deflection and rate at that higher deflection. Members here have had to have new Eaton springs " De Arched" .
Eaton now offers their factory springs in a 1-2 inch drop, which it isnt really.
If I was ordering a set today ( probably will be for a buddies 1970 that's in 4wd mode with new Eaton springs) , I would order the Esprit rear springs for 73 with the 1 inch drop. that would get you about 1 inch below level and a soft enough ride to enjoy and still have a sway bar for handling.
iF YOU WANT SCCA racing OR Drag racing, you can find a lot of "harsh riding" options out there.
1972 > Y99 got you slightly higher spring rates, bigger bars, but same height.
hope this helps..
In 1970 the Chevy F41 suspension package was used on the T/A and a separate option on the formulas. ( this probably has a few pages of discussion, and Im not sure there is a full agreement.) There are cars with F41 and 14 " tires and 15" tire Formulas without the F41.
F41 dates back to the 67 Z28 in Chevrolet as I recall. Chevy installed it in some 6 cylinder stick Camaros with Z stripes to sell during Indy as "Pace setter" sale Camaros... ..