Independent Rear Suspension for a 70 Mustang

[funcars]

I have a 1990 C4 track car with an IRS and a 1970 mach I with leaf springs (currently) and a heavily modifed front end. I've taken both cars road racing a lot and the solid rear isn't that bad. I'm also running a black gold torque sensing diff with global west spring bushings and they help a lot. The only time there is really a substantial difference is cornering on really bumpy roads. Otherwise the IRS isn't really a large benefit.

Leaf springs for lateral location still are not good for the track so I'm going to a torque arm with a watts link and a cambered rear. For the street it's probably not worth it. I'd try some simple bolt-on solutions with the solid rear.

Good luck

[wantahertzdonut]

That's good to hear. I know the solid axles can work very well on a track, but some of the setups that I've seen (like the TCP coilover conversion, Global West's Stage 5, etc) just cost a damn fortune. My main interest in a rear suspension modification was started when I saw DVS's IRS conversion kit and then everything went from there.

But as you (funcars) said, for the street some of this stuff isn't really worth it. The more I drive, the more I realize I'm not going to be doing much racing simply because I just enjoy the car in the everyday. I was also thinking that with everything that I will do to the front (tubular control arms, Shelby Drop, bushings, steering, etc) that it would make sense to also do some work in the rear, but spending thousands of dollars on what everyone says are inferior or problem-ridden systems doesn't make much sense.

I really think I'm going to pursue the Watts Link setup if anything. It's simple enough that I can make it myself (big plus!) and it takes care of one of the biggest issues with a leaf spring rear (lateral location). At very least I'll try a Panhard rod for the most simple mod, and see how I like that. I will eventually autocross the car a few times a year so having some work done to the rear will be a help, I hope!

[Maxoctane]

Late model Crown Vics, Marquis' and Town Cars have 8.8s with a watts link. Some even come with disc brakes and traction lok. These cars are all over the salvage yards. Check one out, maybe with your engineering prowess you could fit one under there! Let me know cause I also am working on a 69 Mach One.

[4MuscleMachines]

If you really want to improve the rear end of your car and not go the high-end way, try composite springs from www.flex-a-form.com. They are much lighter than your steel springs and work excellent on street and especially on a track.

Try this link too:

http://forums.stangnet.com/showthrea...posite+springs

[wantahertzdonut]

I'm going to investigate the feasability of carrying over a crown vic watts link into my car. I don't think the entire rear will be compatible because the CV/TC's are 4 link setups, not to mention probably wider. I am not going to carry over an entire 4 link setup and if I did, it would be off a Mustang.

The composite springs are very interesting for a number of reasons. Do you know if anybody using them has to use a sway bar?

[HsvToolFool]

Wantahertzdonut, I apologize for digging up an
old thread and I don't know if you even care
about this subject any more, but I wanted to
comment on installing an IRS on early unibody
cars.

I have a 66 Mustang convertible and I plan to
install a polished Kugel IRS (bling!) as part
of my restomod. I'm doing a lot of research on
this subject (how I found this thread) and even
discovered a few brave souls who've done this
extreme mod to early Mustangs...

www.reenmachine.com

www.stang-aholics.com

Both of these builders appear to have boxed the
rear frame rails around the mounting points and
then welded in brackets for the IRS. In other
words, they mounted the IRS to the existing
stamped frame rails with some minor reinforcing.
I was very gung-ho about this approach until I
began calling local Pro rod-builders to get estimates.

Without exception, the consensus was that old
unibody cars cannot support the focused pressure
points that an IRS demands of a chassis. Once I
considered their arguments, I was forced to agree.

Leaf springs attach to the rear rails at four
points which spreads the weight over a large
area of the rear unibody. A leaf spring also
directs force forward and aft along the frame
rail's length, rather than entirely upward
against the sheet metal.

Most IRS (Jag/Heidts/Kugel, RCC, CWI, Cobra)
have a single crossmember directly above the
differential which carries the car's weight. This
focused weight isn't a concern for body-on-frame
suspensions because the IRS crossmember carries
the load to frame rails made from heavy steel
tubing which is strong enough to carry the load.
The Pros I spoke to believe (and I agree) that sheet
metal frame rails, even with moderate reinforcement,
will eventually fail around these critical mounting points.

Obviously, I've not given up hope. I plan to
remove the stamped frame rails and replace them
with custom mandrel-bent 2x3 (or 2x4) steel tubing
and then add fore and aft crossmembers. Once
this rear clip is welded into the unibody, the
car's weight can be carried by a single IRS
crossmember. The weight will spread through the
entire rear unibody and no stress fractures will
form. I hope.

I've spoken to Art Morrison's tech line and they
can bend the tubing to my design and put together
an entire kit (unwelded) for about $600...

www.artmorrison.com/frames/framekit.cfm

Perhaps it's over-engineered, it's certainly
unreasonable, but it sounds like a fun project
and a very cool ride. Now just give me a year
or two and I'll check back in with a progress
report.

[Stangonline.com]

Ask and you shall receive.
http://www.jktaylor.org/gallery/70-03

[468mike]

I plan on doing the same thing. However I am going to use the complete eng/trans, air ride, steering rack, K frame, etc., from a lincoln Mark VIII.

The reason for doing this is because I am a cheap.
I got a 68 coupe rust free roller body for $500, and the 90K mile lincoln was $500.

I am a painter so the body/paint work is no problem. I all I should need is some tires/wheels, and a interior kit. The total investment should less the 5 grand, including some shelby fiberglass parts for the body.

Mike

[ProTouring442]

I plan on doing the same thing. However I am going to use the complete eng/trans, air ride, steering rack, K frame, etc., from a lincoln Mark VIII.

The reason for doing this is because I am a cheap.
I got a 68 coupe rust free roller body for $500, and the 90K mile lincoln was $500.

I am a painter so the body/paint work is no problem. I all I should need is some tires/wheels, and a interior kit. The total investment should less the 5 grand, including some shelby fiberglass parts for the body.

Mike

I wish I still had my T-bird, I'd take a few measurements here... Seems to me that this approach makes a lot of sense. The Mark VIII is a unibody, take a whole bunch of measurements, cut and weld, and you have a nice hybrid.

Shiny Side Up!
Bill
'72 442 "Inamorata"

[468mike]

Thanks Bill, I think I will get the plasma cutter out and take part of the shock towers from the lincoln and weld it on to the stang, same with rear (shock mounts).

True, the stang will not be G-machine for killer handling but I don't really care that much, I intend to use it for a daily driver. And being the car is coupe it just isn't worth sinking alot of money into.
I will put the money into the camaro after I decide on the suspension/chassis setup.

I am going to visit Matt at AME next week and check out their stuff.

Mike