Rear coil springs

91AOD5.0LX

I have a slight sag in my rear
Feb 20, 2021
253
128
53
North East
Guys, I have a slight sag in my rear. Car rear that is. Lol
I decided to purchase stock replacement rear coil springs to see if this helps. They arrived today and I noticed they say direct replacement for my 1991 LX 5.0 but then it says “accept variable rate”.
I had no idea what that meant so I dug deeper and of course my car has variable rate rear springs as indicated on my window sticker when the car was new. See pics below of the springs I purchased. I should have looked into this before I bought them but I didn’t know there were different kinds. Anyway, it’s a hassle to return them if thats even possible so does anyone know if it would be ok to install these or if they won’t fit at all? If they do fit, what would be the downside to them being the wrong kind or at the end of the day does it not matter? If it’s that serious i will just buy the correct ones (variable) and see about returning these which I believe are considered “constant”.
any info is appreciated and feel free to break my shoes for not knowing there were different kinds. Lol Once I typed in my make/model/year and it said it fits the car i went ahead and ordered without looking any further.
Thanks in advance
 

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KRUISR

5 Year Member
Apr 16, 2015
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Constant rate springs will work. You likely will not tell the difference. The theory of variable rate springs is two different spring rates in one spring. It gives desired load carrying rate and a softer rate to soak up slight bumps in the road. Technically smoother overall.
 
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7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
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Kearney, NE
The variables give a bit then hit the stronger rate part, (like FMS B springs). The constant rate ones bolt in the same, and are supposed to be better for performance situations. Either one should help your sag.
 
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91AOD5.0LX

I have a slight sag in my rear
Feb 20, 2021
253
128
53
North East
Kruisr and 7991LXnSHO,
Thanks so much for your info! Glad to know I don’t have to go thru the return process and that I can throw these things in without any concerns that they won’t fit or won’t work. I take her out once every 2 weeks or so for a quick joy ride so if the difference is all sorts of technical stuff then I’m not worried about it being that it’s not a daily driver or racer, etc. Thanks for your quick and basic explanations. I really appreciate the it!
As for you others (lol) I honestly don’t know what “CT” means In this forum but I can guess its some kinda invite to poke at me for my sagging rear end. Hahaha I know i opened the door on myself with that one so bring it on fellas because I’m always down for a great laugh even at my own expense. Lol all good fun.
Thanks for the info guys and if anyone else has insight about the spring situation please let me know because I’m always happy to learn the pros/cons of things.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Done deal dude.
may I also suggest if your rear end is sagging don't shove a spring up your ............ Well, you know.... :stick:
 
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Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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I'm not aware of any OEM Foxbody mustangs that had non-variable rate rear springs, so that note on Moogs part confuses me.


Either way, they will fit fine.
 

91AOD5.0LX

I have a slight sag in my rear
Feb 20, 2021
253
128
53
North East
I'm not aware of any OEM Foxbody mustangs that had non-variable rate rear springs, so that note on Moogs part confuses me.


Either way, they will fit fine.
Thanks for this..... glad to know they will fit... I will bang this out next week.
 

91AOD5.0LX

I have a slight sag in my rear
Feb 20, 2021
253
128
53
North East
I watched all sorts of videos on how to change these rear springs and everyone makes it look so easy. Unbolt shocks and quads and the rear drops down. Well I just spent the whole day trying to do this with no luck. Got the springs out but can’t get enough clearance to shove the new ones in. The rear doesn’t seem to drop low enough. Anyone have any tricks or suggestions?
Even pushing down on the drum I still can’t get enough room. Even to get them out I’m had to beat them with a mallot. Im open to any ideas. Gotta be doing something wrong!?!?!
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
5,372
1,727
194
Kearney, NE
I watched all sorts of videos on how to change these rear springs and everyone makes it look so easy. Unbolt shocks and quads and the rear drops down. Well I just spent the whole day trying to do this with no luck. Got the springs out but can’t get enough clearance to shove the new ones in. The rear doesn’t seem to drop low enough. Anyone have any tricks or suggestions?
Even pushing down on the drum I still can’t get enough room. Even to get them out I’m had to beat them with a mallot. Im open to any ideas. Gotta be doing something wrong!?!?!
Is it hanging on your brake hose? Can you drop one side at a time to get the clearance you need without breaking the brake hose?
 

91AOD5.0LX

I have a slight sag in my rear
Feb 20, 2021
253
128
53
North East
Is it hanging on your brake hose? Can you drop one side at a time to get the clearance you need without breaking the brake hose?
Hummmm I have to look at that. Didn’t think of that (hanging on the brake hose). I tried to drop one side separately but that didn’t work either. Ok, I’m gonna have to tell the wife to wait a few extra minutes before we leave for dinner because I have to check the brake line. Lol
Thanks for that thought my friend. I will give that a look. Definetly don’t want to break the brake hose! Thanks!
 

91AOD5.0LX

I have a slight sag in my rear
Feb 20, 2021
253
128
53
North East
So it doesn’t look like the brake line is the problem. Thanks for thinking of that though!
I just took a quick pic of it dropped. I know it’s ugly under there. Lol
Those are the new springs by the way just laying there. If I push down hard and pry with a screwdriver I can almost get it to pop into the top insolator but almost doesn’t count. I need just about a half inch more space or even a
Little less to make it. With all shocks unbolted and no support underneath it still doesn’t drop enough.
 

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