71 Mustang front shocks are destroying top bushings

[Hemikiller]

Although it doesn't look it, the tape is lined up with the top end of the stud.

The KYB Gas Adjust measures 37.5cm from the end of stem to bottom of the mounting plate (and 40 cm to the end of the mounting studs, but the studs don't really add anything to the effective length of the shock.) So, it would appear the KYB's are at least as long or a little longer than your Motorcraft shocks, which looks to be 36.6cm to the bottom of the mounting plate. You can also see that the length of travel is about 3.75" or 9.5cm.

I guess that rules out the shocks as the cause of the problem, leaving the bushings, the springs or some anomaly in my frame/suspension. I am going to try the poly bushings first, till I get the car on the road for a few hundred miles. If that doesn't work, I will look for a different set of springs. Thanks again for all of the kind input from everybody. -Andy

Measure from the lower face of the bottom plate and top face of the stop where the lower washer sits on the shaft. That's the measurement that will matter, as the studs and overall shaft length can vary from mfr to mfr.

FWIW, destroying the bushing is pretty common if the car has the suspension hanging, or sitting without an engine in it for extended periods of time. It's completely outside of the intended function of the bushings. Sometimes the even fail just from normal driving....

 

[71BossPrototype]

Good points. I checked my shock tower caps and the holes are round, and not worn looking (but it sure is a large hole !).

You are correct about measuring to the ridge on the shaft, and I should have caught that. Also, it is true about leaving the car sit without the weight of the motor, and I have had that experience too. I had others report about the bushings getting eaten by normal driving too. They also reported that using the poly bushings cured their problem. I am also debating cutting some of the spring at a much later date, after it has been on the road a while. Thanks ! -Andy

 

[71BossPrototype]

I don't think the extended length of a different shock is going to make the condition worse by bottoming out on the frame rail. The front strut bar and stabilizer link will help support the suspension and if it did touch , it's not going to hurt it. Unless you are jumping a creek and your suspension is unloaded but then you might have a bigger problem than being concerned if your control arm is touching your frame rail when you land it.

The extended length range on just those links that I posted are between 12.2", 12.625" and 13.9" They are specifically made for the "73" in those examples. I have not tried comparing the other model years but I found it interesting that there was a wide range in the length. I'm not sure why there are such differences. I've never come across that before and thought if you needed shocks for your car they were all the same in length.

Unloaded suspension before I overhauled and detailed it. Note: the control arm is touching the frame rail.

Loaded suspension after overhauled. I don't have a picture of unloaded suspension after the overhaul but I can say it's not much different than in this picture. The shock travel is shorter.

After taking Hemikiller's advice, I revisited the tape measure and found the KYB's and the Motorcraft both have exactly the same length of 30.5cm from the bushing stop to the mounting plate. I also took a close look at Terlingua_RS' photos and I agree, the old shock has the longer travel that would eliminate the problem once the upper control arm rests on the frame rail edge. That's how my 70 Mach1 is designed too. The shocks listed don't vary that much in length, but I will take some measurements to see how close to the frame rail it comes with the current shock. Thanks. -Andy

 

[mjlan]

This is an odd problem for sure. This is what my 72 looks like, pretty sure it's all original save for the shocks...

 

[Jeff73Mach1]

I fail to what difference engine in or out makes when the problem occurs when the car is jacked up. Supported on a jack the suspension is under no load with or without the engine.

I wonder if the control arm should be hitting the frame rail, but is not as a result of a difference in design from the stock arm.

If it were mine I might put in a bump stop just to eliminate this.

 

[71BossPrototype]

Mjlan- thanks for the photos. I see there is only a short amount of the shaft showing above the cap. Question- If you put the washers and bushings on the shaft, and pull the shaft up to the normal installed position ( so the bushing-stop is up against the bottom washer, and the top bushing is snugged up) will the bushings still allow the control arm to rest on the frame rail ? That's how mine get messed up, and the arm never reaches a rest on the rail.

Jeff71Mach1- I agree that a snubber or stop could be fabricated to catch the falling control arm before the stress reaches the point of damaging the bushings. But I was hoping there was a simpler solution, like finding a shock with a longer travel. It just doesn't seem like a modification should be necessary to allow one to jack up the car without damaging the shock bushings. And you are certainly correct that weight of vehicle is not relevant to this problem. Also, the arm design seems the same as the original. -Thanks for the replies.

 

[mjlan]

Assembling the washer and bushings doesn't noticeably change the arm or spring length.

That's why your situation is tripping me out.

There shouldn't be a way that the shock would be too short. Have your upper arm mounts in the shock tower been lowered?

 

[71BossPrototype]

Assembling the washer and bushings doesn't noticeably change the arm or spring length.

That's why your situation is tripping me out.

There shouldn't be a way that the shock would be too short. Have your upper arm mounts in the shock tower been lowered?

No mods have been made to the car. The reason I mentioned installing your hardware is that your shock shaft doesn't really look long enough to get the bushing, washer, nut and locknut on the threads that are showing in your photo, (unless there is more travel left in the shaft) without raising up the arm a little. I'll see if I can post a photo of mine. Thanks. -Andy

 

[72HCODE]

I think I have a large washer that sits on top of the bushing and keeps it from pulling out when the car is jacked up

 

[Hemikiller]

My solution, knowing that the bushing could fail when having that much force placed upon them for extended periods, would be to either A) replace the bushings with urethane or B) remove the upper nut and bushing hardware before jacking.

Another option would be to fabricate the upper arm braces that Ford shows in the shop manual, to be used when servicing the ball joints. They would stop the arm from dropping below a certain point and won't place any stress on the shocks or bushings.

 

[71BossPrototype]

Okay, it's been a while since I posted about this problem. Since then, I got the car on the road and it seemed to handle well, steering had a good feel to it, car was stable when braking, and just looked like it was a little high in the front end. Figured it would relax after a while. So, I'm under the car looking things over when I noticed the tires were practically rubbing the end of the Upper-Arms at the ball joints. Turns out, the P.O. who purchased a complete front suspension kit from some place back in around 2002 was sent the 4-rivet ball joint arms. I wasn't smart enough to know the difference, so I used the stuff. Well, I ordered new 3 rivet arms, but then I really had to battle these springs. I remembered how tough it was when I took them off and re-installed them a couple of years ago. I ordered a new set of Eaton springs from NPD and they just arrived. Ya think this was causing the bushing eating problems (the new ones are on the left):

By the way, I purchased the spring removal tool on ebay from the guy in Sturgeon Bay, WI. It cost 85.00, and is well worth it. Takes all the drama and danger out of removing the springs, even the giant ones that I had on there, and they were under tremendous pressure when compressed to remove! Real killers ! I'll let you know how things work out after I put the new ones on.

 

[Stanglover]

Read the post "Top Shock Bushing" (below in previous posts)

I have KYB Gas-Adjust shocks and have absolutely ZERO problem with bushing breaking up. One thing I can tell you from my own experience working on my car is that the springs are critical. The so-called correct aftermarket things that vendors are trying to sell as "correct" are far from it. Those taller, but smaller diameter wire springs will not work the same as the original spec height / wire diam. In my case, I re-used my original springs as they were in as new condition. If you need springs, buy Eaton Detroit Springs. NPD sell them. They (Eaton) will spec the EXACT spring for your car and weight. You can go the their website and look up what you need or just call them directly.

If your steel bushing caps are cutting the rubber, then surely the caps are too small in diameter. If they are larger than the compressed bushing, then they can't cut into rubber. If they are the correct ones, then maybe the bushing are being installed incorrectly which allows them to move in the top plate hole.

Anyway, hope that helps some good luck sorting it out,

Geoff.

 

[71BossPrototype]

Hi Geoff. The smaller springs depicted on the left are the Eaton springs from NPD. You can see the obvious difference in sizes. By the way, it wasn't the steel bushing cap that was cutting the rubber bushing, it was actually pulling the bushing through the hole in the top of the shock tower cap, like a cookie cutter ! I'll let you know how it goes with these Eaton springs after I get them installed. Thanks for the input.

 

[Stanglover]

Hi Geoff. The smaller springs depicted on the left are the Eaton springs from NPD. You can see the obvious difference in sizes. By the way, it wasn't the steel bushing cap that was cutting the rubber bushing, it was actually pulling the bushing through the hole in the top of the shock tower cap, like a cookie cutter ! I'll let you know how it goes with these Eaton springs after I get them installed. Thanks for the input.

I see!! That's weird that the bushings are pulling through the mount plate hole. Not seen that one personally. Could it be that the way too tall springs were putting so much load on the shocks? I know when I tried to install the tall shocks that were supplied with a Scott Drake front end "kit" I bought, there was so much difference that it was hard to get the shock bolted up. Besides the ride height was way off. That's when I talked to a tech at Eaton and found that my original springs were still okay. Ride height back were it was and no shock issues other than I described in the previously post mentioned.

I hope that your issue will be solved once you put the correct springs back in. Talking of, did you check the listings yourself for the correct Eaton spring? sometimes the sales guy at NPD may just give you what's in stock. There are several springs similar.

All the best,

Geoff.

 

[71BossPrototype]

Talking of, did you check the listings yourself for the correct Eaton spring? sometimes the sales guy at NPD may just give you what's in stock. There are several springs similar.

Good point. I will check on that. Thanks! Let you know when I get back on it. -Andy

 

[Stanglover]

Talking of, did you check the listings yourself for the correct Eaton spring? sometimes the sales guy at NPD may just give you what's in stock. There are several springs similar.

Good point. I will check on that. Thanks! Let you know when I get back on it. -Andy

Andy, yes definitely worth checking for the correct springs. Chance are you have the right ones, but..........!

This is what pees me off with the aftermarket suppliers. They are all trying to sell stuff as fitting 67 -73.. yeah right!! I say sell the right parts for each year or not at all.

I have spent 8 years now sorting through all the wrong parts to find the right parts for my 71 Mach 1.

Anyway Andy, hope you get it sorted and back on the road where it belongs soon.

Geoff.

 

[Kevin J]

Considering the configuration of the suspension I don't understand why everyone is not having the same problem. My shock bushings are also compressed to the point of destruction. When I look at the design of the suspension though, there is a travel limiting bumper that contacts the upper control arm if/when the suspension is compressed dramatically, but unlike GM products, there doesn't appear to be any bumper (perhaps between the upper control arm and the frame) to limit the maximum extension of the suspension. That being the case, the only limit to the extended or uncompressed travel would be the shock absorber. My car rides and handles fine, until I put it on a lift - then the suspension hangs and the upper shock bushings often crush and tear off.

Still working on a solution but I too have KYB's so I'm inclined to try a shock with the factory extended length.

 

[Don C]

Have you verified that the hole in the shock mount is the correct size, and not too big? Measure what the diameter of yours is and post it, so someone can check against theirs.

 

[72HCODE]

" there doesn't appear to be any bumper (perhaps between the upper control arm and the frame) to limit the maximum extension of the suspension"

there is. it is part of the shock tower covers.

but it limits upward travel only.

for people with the shock bushings pulling through they either have springs way too long or heavy or wrong front shocks with the throw too short.

most cars are totally missing the shock tower covers. they rust out and mechanics usually tossed them out. they help re-enforce the front shock towers add bracing and they hold the rubber bumper which hits the top suspension arm to prevent bottoming out.

don at ohio has them

Item #M425L

http://ohiomustang.com/store/order_page.asp?itemid=1107

Item #M425R

http://ohiomustang.com/store/order_page.asp?itemid=326

the bumper

http://ohiomustang.com/store/order_page.asp?itemid=1003

 

[piper62j]

I ran into the same problem with the front shock upper bushings.. The aftermarket rubber bushings are made of an inferior compound compared to the oem.  Also, the aftermarket dimensions are not equal to oem in most cases and are smaller.. The steel washers are also smaller in diameter..

I ended up pulling some older oem bushings out of my junk box and have had no further problems.. The KYB and comparable bushings appear to be beefier and will probably work fine..

Wish China manufacturers could read our blue prints correctly..