Vintage Mustang Forums banner
  • Hey everyone! Enter your ride HERE to be a part JUNE's Ride of the Month Challenge!
  • May's Ride of the Month contest ended with a tie! Go to this thread to vote on the winner! VOTE HERE

1 - 18 of 18 Posts

·
Registered
1971 302 C4 auto convertible, Grabber Blue/white/white
Joined
·
164 Posts
Discussion Starter · #1 ·
Hello all, I am looking to possibly purchase this 1972 convertible. It has the classic rear end sagging look to it. I read in the forum here that many people replace the rear leaf springs with a revised set. Is that generally the fix for this sort of Sagging rear end? And will the front end settle back down when I get the backend to lift up a little?

793365
 

·
Registered
Joined
·
21,426 Posts
From the factory, there would have been many different springs available depending on the options in the car. When you order from the aftermarket, you're getting a one size fits all made by different companies in different countries so it's a crap shoot unless you order from Eaton springs who use the correct spring steel made in the USA from Ford blueprints.

A common problem in the front is that people tighten the lower control arm bolts with the wheels hanging. The rubber bushings don't like to twist so where ever they're tighten, that's where they like to stay. They add artificial spring rate.
 

·
Registered
1971 302 C4 auto convertible, Grabber Blue/white/white
Joined
·
164 Posts
Discussion Starter · #3 ·
From the factory, there would have been many different springs available depending on the options in the car. When you order from the aftermarket, you're getting a one size fits all made by different companies in different countries so it's a crap shoot unless you order from Eaton springs who use the correct spring steel made in the USA from Ford blueprints.

A common problem in the front is that people tighten the lower control arm bolts with the wheels hanging. The rubber bushings don't like to twist so where ever they're tighten, that's where they like to stay. They add artificial spring rate.
Tom, thanks!
The seller is a sweet elderly woman who has a trusted mechanic, he told her the front end needs a refresh…tie rods, shocks, etc…I suspect all sorts of bushings and bearings need attention so it will get a full review if I purchase….she reports the tires are wearing on the insides, so there is work to be done….I am not a fan of whitewalls so upgraded rims and tires would be on the project list too…I found the site and worked through the configuration tool…looks like about $500 for leafs and install kit….certainly doable….
 

·
Registered
Joined
·
21,426 Posts
Tom, thanks!
The seller is a sweet elderly woman who has a trusted mechanic, he told her the front end needs a refresh…tie rods, shocks, etc…I suspect all sorts of bushings and bearings need attention so it will get a full review if I purchase….she reports the tires are wearing on the insides, so there is work to be done….I am not a fan of whitewalls so upgraded rims and tires would be on the project list too…I found the site and worked through the configuration tool…looks like about $500 for leafs and install kit….certainly doable….

The stock alignment specs, well they just plain suck. A big problem is the location of the upper arm, it's too high. The cure is to lower it 1 inch. What this does is limits the unwanted positive camber gain. It pushes the top of the tire out into the fender, not what you want. By lowering it, substantially reduces this. This will greatly improve handling while reducing tire wear. The good news it doesn't cost anything other then a drill bit. Add some caster and you'll have a fun car.
 

·
Registered
1971 302 C4 auto convertible, Grabber Blue/white/white
Joined
·
164 Posts
Discussion Starter · #6 ·
Good luck with the car, keep us updated!
Thanks, I have been tossing prospects and ideas and questions around and you guys are great…I am selling my 2015 GT to get into a classic for retirement…a cruiser instead of a high performance almost track car…so eventually I will be here with a real car, not an idea!
 

·
Registered
Joined
·
2,488 Posts
You could lower the front... drop a big-block in it :)
Keep us posted.
 
  • Like
Reactions: RIBS and rpm

·
Registered
1971 302 C4 auto convertible, Grabber Blue/white/white
Joined
·
164 Posts
Discussion Starter · #9 ·
We have a Build Forum for projects like this. Start a thread, I'd like to follow.
I will when I have a car. LOL. This one is a days drive away, an I have to work for a living! 😀
 

·
Registered
67 Fastback T5 331 TCI Frt End, Canted 4 link rear susp
Joined
·
713 Posts
That stance with the rear lower than the front is so common, seems unlikely all of them resulted from tightened lower control arms while in the air...
 

·
Registered
Joined
·
2,216 Posts
I agree that the front seems a bit high. Is it possible that the trusted mechanic replaced the springs years ago and the lady forgot? It's a common misconception that classic Mustangs were higher in the rear than the front. The earlier the car, the more likely the rear was low. Search Google for old Mustang magazine ads and you will see this without question. In 1965 only the Shelby sat level. The 71- 73 cars seem to have a near-level stance. Maybe just a tad higher in the front, if at all.

There is a large number of coil and leaf springs available today. Few of them will give your car the right stance. So you will probably need to add coil and leaf springs to the list. Please get advice on the forum before purchasing any spings.

 

·
Registered
1971 302 C4 auto convertible, Grabber Blue/white/white
Joined
·
164 Posts
Discussion Starter · #13 ·
The stock alignment specs, well they just plain suck. A big problem is the location of the upper arm, it's too high. The cure is to lower it 1 inch. What this does is limits the unwanted positive camber gain. It pushes the top of the tire out into the fender, not what you want. By lowering it, substantially reduces this. This will greatly improve handling while reducing tire wear. The good news it doesn't cost anything other then a drill bit. Add some caster and you'll have a fun car.
Tom, I am new to the classic Mustang, can you explain the drill a hole drops the front end process?
 

·
Registered
Joined
·
10,484 Posts
Tom, I am new to the classic Mustang, can you explain the drill a hole drops the front end process?
Tom is talking about what is called the Arning Drop, or Shelby Drop, that is done to the 65-70 cars. The upper control arm mounting holes are redrilled 1" lower, which improves the suspension geometry. It will also lower the front a small amount.

However, the 71-73 cars had their suspension geometry revised and the Arning/Shelby drop is not needed, nor can it be done without cutting up the internal bracing of the shocktower. A new set of factory style leafs will bring the rear end back up where it belongs, and will lower the front a small amount. NPD sells application specific leaf springs, in both the "economy" style, and the Eaton exact replacement type.

FWIW, the most important thing you should be looking for is rust. Convertibles have an inner rocker panel that provides support to replace the lack of a roof, and it is critical for it to be solid. Replacing these inner rockers is an expensive and time consuming job.
 

·
Registered
Joined
·
21,426 Posts
Tom, I am new to the classic Mustang, can you explain the drill a hole drops the front end process?

Sure, you're drilling new holes. Start off with a 1/8" then go up to something like 1/4" or 5/16" then to the final size 17/32". Some guys use 1/2" as it's common, the 17/32" is not as common about $15. The 17/32" is really preferable. Here are a couple images, one shows the relationship of the control arms before and after. You can see in the image on the right as the suspension compresses, the upper arm will swing towards the engine pulling the top of the tire in. This is what happens to the outer tire in a turn. This allows the tires to bite into the road instead of being easily dragged due to loss of grip. Also there is what's called the roll center, a imaginary point where the car wants to rotate on. The Arning modified raises this point a little bit making the car more inherently stable. Kind of like spreading your legs with someone pushing you sideways instead of having your feet together.





794006


794007
 

·
Registered
Joined
·
3,338 Posts
OK I thought that the 71-73 mustangs didn't need the Shelby drop as it uses the Torino platform and a different suspension.
 

·
Registered
Joined
·
10,425 Posts
Good question. I think guys have done it but maybe not needed as much if at all. @GT289 will know
We did hang the original Negative Roll tubular upper arms on a couple of 71-73 cars. (MNR-73) Those are dropped via
template and cover the 67-73 cars.
The same "rules" apply to all those cars, although I have never done an actual ARNING drop on a 71-73. The only platform
I'm aware of that is a real PITA to move upper arms on is the Maverick, the shock towers neck-down..... they're a real treat.

ex-Global West GM
1991-1995
 
1 - 18 of 18 Posts
Top