Rear leaf spring inquiry

[70cobrascj]

Looking for input from those who have replaced their rear leaf springs with new ones from Eaton Detroit Spring.
I’m sure my original 52 year old springs have sagged. I would like to know from those who have replaced them with stock ride height springs if it made a difference in the way it sat?
I’m looking at getting the stock ride height ones. But would hate to have them not raise the rear a little.
Thanks for any all input.

 

[Stanglover]

Looking for input from those who have replaced their rear leaf springs with new ones from Eaton Detroit Spring.
I’m sure my original 52 year old springs have sagged. I would like to know from those who have replaced them with stock ride height springs if it made a difference in the way it sat?
I’m looking at getting the stock ride height ones. But would hate to have them not raise the rear a little.
Thanks for any all input.

Absolutely. Eaton Detroit Springs were an OEM supplier. They can custom make any spring you want or you can order the stock spring rate for your car.
Your Mach 1 ought to have 138lbs 4 leaf springs. I would stick with them. They offer different eye locations as well. You can even call them to discuss what you want.
On my Mach 1, I decided to install 158lb Boss 351 springs because at that time, the rear axle was an open 3.25:1 and I wanted to avoid wheel hop. I find the 158lb spring just a bit too harsh on rougher roads, but they are really nice on smooth, curvy roads.
I learned the hard way about springs, spent, no wasted money on Grab-A-Track 4 1/2 leaf garbage only to have them start to reverse bend in only a couple of years.
Whilst you're at it and being as you have a Mach with comp suspension, I would swap the sway bars at the same time. Addco make very good sway bars and now offer a revised 7/8" rear bar thanks to our member friend, Jpazz. Add a 1/18" up front and that car will handle way better. I did buy the Eaton 1" longer shackles as well, but that only raises the center wheel arch about 1/2". Any longer shackles, and they will show under the rear end.
One more thing on mine, I did install all new front suspension, but ended up keeping the original front coil springs as they were still to spec. Don't fix what ain't broke.

 

[70cobrascj]

Absolutely. Eaton Detroit Springs were an OEM supplier. They can custom make any spring you want or you can order the stock spring rate for your car.
Your Mach 1 ought to have 138lbs 4 leaf springs. I would stick with them. They offer different eye locations as well. You can even call them to discuss what you want.
On my Mach 1, I decided to install 158lb Boss 351 springs because at that time, the rear axle was an open 3.25:1 and I wanted to avoid wheel hop. I find the 158lb spring just a bit too harsh on rougher roads, but they are really nice on smooth, curvy roads.
I learned the hard way about springs, spent, no wasted money on Grab-A-Track 4 1/2 leaf garbage only to have them start to reverse bend in only a couple of years.
Whilst your at it and being as you have a Mach with comp suspension, I would swap the sway bars at the same time. Addco make very good sway bars and now offer a revised 7/8" rear bar thanks to our member friend, Jpazz. Add a 1/18" up front and that car will handle way better. I did buy the Eaton 1" longer shackles as well, but that only raises the center wheel arch about 1/2". Any longer shackles, and they will show under the rear end.
One more thing on mine, I did install all new front suspension, but ended up keeping the original front coil springs as they were still to spec. Don't fix what ain't broke.

Yeah I replaced all the front suspension and steering already with just new shocks in the back. I even put new Eaton springs up front. It’s time now to replace the rear stuff and just want to know how everyone’s experience was with stock ride height springs.
Thanks.
Does the new Addco rear bar use the original mounting locations since mine is a original rear sway bar car?

 

[73MustangCoupe]

I went with the Eaton Detroit stock front and rear springs for the Rickster. A while back I measured the height of the body relative to the hub on both front and back, and both are within about 1/8" of factory specs. The spring rate they recommend for stock replacement is a perfect ride, for me, and I'd go with it all over again.

 

[Stanglover]

Yeah I replaced all the front suspension and steering already with just new shocks in the back. I even put new Eaton springs up front. It’s time now to replace the rear stuff and just want to know how everyone’s experience was with stock ride height springs.
Thanks.
Does the new Addco rear bar use the original mounting locations since mine is a original rear sway bar car?

Sway bar uses the exact same locates. I did need to drop one side of the exhaust pipe, right I think, to wriggle the bar through. Other than that it was an easy swap.
As for the other parts, sounds good.
If you order the Addco 990 rear bar, make sure it is the new revised bar. I ordered directly from Addco.
Below is the revised bar showing a longer straight part where the clamp is.

 

[Idaho Chris]

Unless you go custom, Eaton offers three OEM spec rear leaf spring packages; standard, competition and Boss with progressively stiffer spring rates. I chose the competition version as I was worried about the harsh ride (as Geoff describes above). I am happy with my selection as it seems to offer the best compromise for my tastes.

The new springs did indeed change the stance of the car. After 50 years my springs had sagged a bit, but even more troublesome the car did not sit level side to side as the springs did not sag evenly.

New springs fixed the stance and I now sit level side to side. As others have noted, you get what you pay for. Go Eaton and you will have no regrets.

 

[midlife]

If there is a good rear end/suspension/truck repair facility, inquire about having your existing springs re-arched: a lot cheaper than buying new.

 

[Stanglover]

Referring to the Addco 7/8"rear sway bar, I forgot to mention that it fit very close to the cross frame member that supports the gas tank. I found it restricted the position of the vapour return line. All it needed was an extended bushing of some sort that holds the tube clear of the sway bar. No big deal, but necessary.

 

[lectricegg]

I didn't change my springs, but changed the shackles, u-bolts, and bushings. Those changes raised the back of the car about 1/2", which was noticeable at the wheel arch. My rear spring bushings were totally shot.

 

[c9zx]

All Mustangs of this era were tail draggers from the factory. Why I do not know. Chuck

 

[roboconklin]

All Mustangs of this era were tail draggers from the factory. Why I do not know. Chuck

Mine blew sparks at the drag strip line as the factory rear tie down braces hit the track. I had 10x15 wrinkle wall slicks on it. That was in the 90’s. I’m too old to race now.

 

[Stanglover]

All Mustangs of this era were tail draggers from the factory. Why I do not know. Chuck

Maybe someone screwed up with the spring arch. The rear springs are quite "flat" in that regard.
By contrast, those Grab-A-Crap springs I bought, were way too arched and lifted the rear 2" at the center point. I added 1" lowering blocks and to be honest, the car looked good at that.......... until the springs started to de-arch themselves.

 

[Stanglover]

Just for shits and giggles, here is a pic I found of my 72 Mach 1 (the one that got away).
This car had stupid long shackles on it, but actually raised the back to where it did look "right", but spoiled by the shackles showing below the valance, arrowed. The pic is a bit dark, but best I could do to lighten it.

 

[Don C]

As Chuck stated, the rear ends were low from the factory.
The factory dimensions to back this up are in this thread:
https://7173mustangs.com/threads/underbody-dimensions.28786/#comment-295892