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View Full Version : Mark I Rear Suspension Help



GrooveM
07-21-2024, 09:22 AM
I have a Mark I that has a 1992 GT engine and transmission and a 1999 GT rear end. I noticed last weekend that the drivers side rear seems collapsed and the shock and wheel well both measure about 1” lower than the passenger side. This is definitely a change within the last 3 weeks. As for why this condition has recently manifested, all I can say is that Wisconsin winters are not kind to our roads and this year they seem even worse than in years past. I’ve put on just over 5000 miles in the last 3 years. Before that the rear end had less than 1000 miles on it. My questions are:
1. Is this typically a coil spring issue or the shock or both?
2. How do I determine the correct replacement springs? I have wire diameter, OD, relaxed length and they are pig tail on one end. See pics.
3. What is a good source for standard length springs? Everywhere I look they are selling lowering springs only.
4. Should I use spring dampeners on the bottom for the pigtail and spring silencers for the top? There were silencers on the top side that have disintegrated.
5. Is anyone familiar with the type of springs needed for the spring tubes with a helical ramp like the ones from my pics? Looks like a progressive rate spring with flattened ends opposite the pigtail.
The shocks seem to be easy to identify and find. Just a matter of how much I want to spend.
Any help with spring identification would be greatly appreciated. :)
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A couple of things I just remembered. I have been searching for springs assuming they were from the 1999 rear end with no luck. However, when I put in 1992 Mustang GT the springs I found seem to match pretty close. Almost like the builder did a mix and match between years. No. He did not give me the complete list of parts and receipts. Before you get on me about that please understand that I was just coming off of cancer surgery when I found this car and needless to say, my mind wasn’t 100% at that time. The car has been just what I needed at that time and I still love it.
Spring dims: wire diameter 9/16, OD 5.00”, free lg 12.50” (could be a little collapsed?).

Jeff Kleiner
07-21-2024, 10:36 AM
Those would be Fox body Mustang (1979-1993) springs. This configuration is rarely used on our cars these days however, and when they are they are kind of known to be difficult to hold into adjustment. Unless you're really trying to get by on the bare minimum expenditure I suggest that you consider getting rid of them, the Mustang shocks and the horizontal quad shocks and replacing the whole works with the FFR Koni coilovers along with the correct axle brackets which will mount the bottom in double shear.

Jeff

PG_Cobra
07-21-2024, 12:09 PM
I'm still using this spring configuration on my MK1. I have clamps that lock the spring on the tower so height gets retained. Also using 02 Mustang Bullit 200lb linear springs. The Fox springs are variable rate and are way too soft IMO.

CraigS
07-21-2024, 01:35 PM
PG has some good info. I had Fox springs in my MkI and they were quite soft. 200# in that location would still be soft as 200# or 250# was the standard when coilovers became popular. So 200 in the stock location might work more like 150-175 because of the leverage ratio. I also liked the clamp idea.

GrooveM
07-21-2024, 02:11 PM
I'm still using this spring configuration on my MK1. I have clamps that lock the spring on the tower so height gets retained. Also using 02 Mustang Bullit 200lb linear springs. The Fox springs are variable rate and are way too soft IMO.

Do you by chance have some pics of those clamps and any info/part number for the springs? I will probably go the route Jeff mentioned but until I’m ready this might get me through the rest of this summer.

GrooveM
07-21-2024, 02:15 PM
PG has some good info. I had Fox springs in my MkI and they were quite soft. 200# in that location would still be soft as 200# or 250# was the standard when coilovers became popular. So 200 in the stock location might work more like 150-175 because of the leverage ratio. I also liked the clamp idea.

Jeff,
Thanks for the quick reply and suggestion. That sounds like a direction I would prefer to go. I prefer cool over shocks for easier adjustability. Do you have any info or pics so for me to start looking for the components and what it will take to make the swap?

David Williamson
07-22-2024, 03:08 PM
Contact FFR they have the Koni coil overs and the parts to adapt them, all simple bolt in stuff.
David W