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Mustang II Kit Failure

84K views 108 replies 45 participants last post by  grandpaws 57 
#1 ·
Some months back we had a long thread on Mustang II kit failures and I had expressed great confidence on the kits, if properly installed. Well, I had one this evening on my way home and will share it with those that may be interested. The 36 Ford 5WC in my Avatar was completed in 1999 and I have put 26,000 trouble free miles on it (til this evening) It has a Fatman's stage 3 kit in it. The 1/2 inch bolt that fastens the tublar lower control arm failed about 1/2 inch inside the cross member on the front side of the XMember and about 3 inches from the bolt head. the back side of the lower control arm remained attached to the cross member, but the front side of the arm went down and out. The wheel assembly tilted out at the top and this fractured the heavy MOPAR upper ball joint seat. The tire took the beautiful paint job to the shiney bare metal on about 10 inches of the wheel opening bead. I was slowing to make a right turn so was only doing about 15 mph and just touched the brake. I jacked the car tho get some relief for the fender and examine the damage. I pulled the bolt end from the control arm eye and saw that it had basically sheared. The bolt had been about 90% sheared for some time from the rust on it and the last 10% was a shiney new brake. The remaining part of the bolt appears to be frozen in the tube that is welded inside the cross member. Now the scarey part: I had driven the car yesterday about 200 miles thru the twisting mountain roads in Western North Carolina and many of these turns at speeds high enough to have a comfortable drift. Great fun, but could have been disasterous. I'll be having a conversation with the Fatman in the AM and see if there other failures such as this. These bolts are grade 5 and the fracture would be indicative of over torque, but since I installed and assembled the front end, I know it was not over torqued.

Trees
 
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#4 · (Edited)
:D



It will be interesting to hear what.....THE CHUBBY ONE has to say.


I am not bashing anyone or their products..........but it does seem to me that he gets MORE than his fair share of these :surprised :surprised

Maybe he sells more than anyone else??



Glad you are OK..:cool:




.
 
#6 ·
I'm very glad no one was hurt.

You're failure is somewhat different than those seen previously but still seems to reinforce the argument that eliminating strut rods may not be the ideal solution to making the Mustang II suspension "look" better.

Keep us informed.

Centerline
http://www.hotrodsandhemis.com
 
#7 ·
seriously, this is the one company I wouldnt buy a kit from, yes I know lots of folks who run The BIGG GUY's stuff, BUT out of all the companies that make M2 kits he's the one I have heard all the complaints about & NEVER anyone else. The odd thing the complaints are, everyone who complained had a different problem w/his kits. SOOOOOOOOOO if it's up to me & I'm using a M2 kit, you know who I WONT buy it from..........joe
 
#8 ·
Why a grade 5 bolt? I know they perform better under certain conditions like tensile loading but honestly why grade 5 for a critical shear bolt like a suspension bolt?

Somethings not right there, are you sure? Does the bolt head has three, five or six ticks on it?

Which one here does it look like?
 
#9 ·
That is why I have been adamant about only using stock MII X-members and hardware in my installations and advising everyone who asks to do the same. These aftermarket guys are probably not engineers and I am 100% sure they don't do fatigue testing to check the long life implications of their designs. I recall one guy posting on a thread similar to this last year that he tested a new suspension he was planning on selling "all weekend, over potholes and rail road tracks" and didn't have any failures so he was confident in selling it to the public.

I know for a fact that Heidt's 'economy' X-member has a serious flaw in design that will invariably fail with enough fatigue cycles. There have been a couple of pictures of the failure posted on this board in the recent past. I am not familiar with Fat Man's design but it sounds from your description that it has some serious long-life design flaws too.

If you have one of these after market X-member, be very diligent in doing your monthly inspection looking for cracks, bends, and evidently, failing bolts.
 
#11 ·
To check the bolts, you only option is to take them out and look at them. The lower A-arm bolts on strut rod eliminator units like Trees' are the most critical and should be checked at least semi-annually. The rest of them are relatively lightly loaded. If you have strut-rods, all the rest of the bolts are probably not over stressed.

The rest of the system needs to be checked for corrosion and cracks. The former is pretty straight forward.

If you have strut rods, the strut rod mounting point on the frame is the critical point. I don't know how many rods I have seen at rod runs that have these mounts cracked and usually not even hanging on the frame. If it is welded to the frame, check that weld. Preferably the bracket is welded and gusseted to a 1/4" or 3/8" plate or 1/4"x4"x4" angle iron and bolted to the frame. Check the body of the X-member around the lower A-arm bolts for cracks also.

Front ends with strut-rod eliminators are living on borrowed time, IMHO. All of the aftermarket X-members I have seen are not robust enough to withstand fatigue stress so will eventually crack. This is totally different from tensile stress. Tensile strength is the resistsnce to being pulled apart by a single load application. Fatigue strength is much more subtle and a lot lower value than tensile strength. In fatigue stress failure, a part is stressed to a level far below ultimate tensile stress thousands or millions of times (could be vibration or just normal service - pot holes, joints in the highway, etc.). Even though none of the individual loads can possibly fail the part by itself, the accumulation of the loads initiates a crack at a stress riser (sharp inside corner, hole, nick in the metal, etc.). Heidt's economy X-member is the worst example I have see. It has right-angle joints in the plates that make up the body of the unit that are in the highest stressed place they could be. Check very carefully around the entire bottom bolt hole area for the first sign of cracks or bending.

Th rest of the system should be ok, just check for problems.
 
#13 ·
horvath said:
Okay -- well, my Mustang II kit was totally welded onto the frame, and my mechanic said the job was done very well ... the geometry is all correct, level, etc.

Does that eliminate some of the concern of what we're discussing?

Alan
54 Chevy Pickup
Nope. The weaknesses aren't a fuction of how well the thing was installed. They are inherent in the unit itself.
 
#14 ·
Thanks, man.

There's a really cool (reputable) hotrod guy about a half-hour from me that I've been meaning to visit. I talked to him on the phone recently and he's very familiar with the Fatman's IFS, so I'm gonna take my truck to him and have him check everything out in detail as you've outlined.

Then, I'll rest easier and drive more comfortably, too!

Alan
54 Chevy Pickup
 
#15 ·
Ok, I have an up date since I have removed all the parts on the failed side. Tomorrow, I strip the other side. First, my dealings with Fat Mans Fabrications. I have been to their facility and will say they are a firsct class operation. They do have a design function and use prototypes and extensive testing. They also do structural analysis and Fatman himself is an engineer with lots of metalurgical background. I explained the problem to a technician, who looked up my record with the company and knew every thing I had purchased and when I purchased it. He proceded to tell me they had problems with some of these bolts in the past and my most recent kit had special 5/8 inch bolts built to made to their specifications so they could maintain quality control. They were going to send me all new bolts (5/8") , bushings, and ball joints, no charge, and that Fatman himself wanted to talk with me as soon as he could break away from some customers. He called me at the shop about an hour later and wanted all the details. He said this was the same type failure as 5 others and they had done metalurgical testing on them and determined they had received a bad batch of bolts that had not been properly heat treated. The part of the bolt close to the threaded end was softer than grade 5 and near the head and the fracture, it was closer to grade 8, which was indicative of flexing (working) hardness. Neither he not the technician tried to BS me and readily acknowledged a discovered weakness and had taken corrective action. He also offered to pickup the tow bill (did not have one) and will pay for the alingment when I provide him with the bill. After talking with him, I discovered the Carrera shock shaft is bent next to the eye and I'm sure there will be a new one here by the time I am ready for it. He did say this was the 6th 1/2 " bolt failure out of approximately 40,000 they have put in service, so their track record is really good. There is one thing I did not do on assembly that I should have done, and you can bet will be done in the future. I did not put any lubrication on the bolt because I did not consider it to be a wear item. This bolt is rusted in (the hole (Fatmans welds a thick wall tube inside the crossmember for the bolt to pass thru). The next ones will be installed with a good coating of Never Seize. For Chuck, the bolt had 3 hashs, signifying grade 5. I, nor Fatman, think grade 8 is the answer because while stronger in tensil strength, they are weaker in shear, which is what became lacking when the bolt work hardened. Going back to some of the other responses. I still think Fatmans is producing the strongest aftermarket units. His cross members are over kill, his thick walled tublar products are indestructable and the MOPAR ball joints are so much better than the flimsey OEM Mustang II. The bolt failure, for what ever reason, can occur on any other kit. Willys 36 is right in that the strut rod geometry of the origional equipment can not be beat ever by strut rod eliminators. Fatman did offer a solution to the cracking of the frame where the strut rod bracket is welded on and that is weld a 1/4 inch plate to the frame and then weld on a 2nd 1/4 " plate to provide the proper thickness for the strut rod bushings etc. This was to reduce the heat required to weld a 1/2" plate to the much thinner frame rail. Thanks for all the information sharing, guys.

Trees
 
#16 ·
Trees, Thanks for the great update and glad your alright. I drove some of those hills and know the turns are tight and the hills are steep.
Another check on the bolts with fatigue is the working bolt. With the fatugue the bolt can loosen due to minature vibrations and sometimes start the hole to elongate. If the bolts have been worked for a long time, a measure check on the hole is needed and the hole may need sized to the next size bolt.
 
#18 ·
Excellent news, great info.

I called Fatman when I first got my truck and was trying to eliminate a shimmy problem ... being such a greenhorn, I was asking obviously uneducated questions and those guys were so gracious and understanding with me, it was surprising! They very patiently listened carefully to be sure of understanding what I was after and answered me with great clarity. Not only a good IFS, but a great bunch of people, too.

Alan
54 Chevy Pickup
 
#19 ·
Great news Trees. Like I said B4, I am not familiar with Fat Mans X-member but it sounds like he has his ducks in a row. I even like his approach to the strut rod mounting - recognizes the weakness and proposes a proper solution. Can't say I am as high on Heidt's stuff from all the info I have gathered to date. IF I ever went with an after market unit, that is the depth of investigation I would go with the manufacturer B4 I laid down a single red cent. Nest time you talk with him you might suggest he put together a technical sales brochure detailing all of the engineering and testing credentials you described.
 
#20 ·
The part of the bolt close to the threaded end was softer than grade 5 and near the head and the fracture, it was closer to grade 8, which was indicative of flexing (working) hardness.
the bolt had 3 hashs, signifying grade 5. I, nor Fatman, think grade 8 is the answer because while stronger in tensil strength, they are weaker in shear, which is what became lacking when the bolt work hardened.
Ummm...thats a bunch of HOOOEEY!. Grade eight bolts outperform grade fives in every regard except for the Charpy impact test. If he was truly looking for exceptional performance in the Charpy test he would have used a forged structural bolt like a A-320 bolt which also outperforms the grade 5 in every regard. From his lack of concern and failure to take action in proactively searching out all those with the poor quality grade 5 fasteners he seems like more of a lawyer than an engineer. Five complete structural failures in 40 000 for a critical suspension component would mean a massive recall to a manufacturer like one of the big three. I think his product was never tested to failure if you ask me and he is terrified of that coming out in a court room. Funny how they always offer to bend over backwards to pay for the minor inexpensive inconveniences when you could have been killed by their faulty product.

Sounds like he is more concerned with a lawsuit than solving the problem and preventing deaths.:skeptic:

What else is new?:rolleyes:

I would be interested in an online interview with the "Fatman" to discuss this matter if he is interested? Invite him over?;)
 
#21 · (Edited)
Once again 4 Jaw Chuck is correct. The link below will run you through a comparison of Grade 5 versus Grade 8 as related to shear.

Grade 5 vesus Grade 8

Since it would be nearly impossible to fatigue this fastener in 26,000 miles under normal circumstances (unless you spent all your time off road), I would look to installation technique, proper design of bolt size versus grade and/or manufacturing flaw in the original bolt. What's most interesting is that you stated it had failed through 90% of the cross section sometime earlier based upon rust in the shear area.

Another comment that troubles me was "the fracture would be indicative of over torque". This is a common misconception. Fatigue failures are more commonly accelerated by under torque.

The most telling info in the "fix" was not a properly heat treated Grade 5 bolt direct replacement, but was a properly heat treated Grade 5 bolt 1/8" larger in diameter.

I don't know the circumstances of this failure and therefore won't comment, but the misinformation on different grade bolts in shear does a disservice to the rodding community. Everything else being equal, I'll bet my life on a Grade 8 bolt over a Grade 5 bolt any day.

:)
 
#23 ·
Chuck, 32 Vicky, Willys, good info. Willys, Fatmans cross member is made from 3"X4"X1/4" tubing and has the thick wall tube welded in as per your attachment and the end is welded up also. My lower arms fit on the outside of the cross member and does not have the extenders Adding the gussets/end braces for the bolts look like a good additional safety measure. Having a grade 5 bolt failure that was not properly heat treated is not the same as having a true grade 5 failure. Unfortunately, we are in the age of being victims of substandard products from overseas where quality control is non existant. Remember airliners jet engine attachment bolt problems? Our aircraft industry has horror stories about repairs being made overseas with substandard parts!!! When a bolt such as this fails 3/4" inside the hole away from the shear stress point, you have to wonder why other than bolt too small, too much torque, not enough torque, grade 5 vs grade 8. The threaded end of the bolt bent about 10 degrees and I used a 3 ft long cheater to bend it back straight and it did not fail. I still am trying to get the remaining bolt out of the hole and so far it has not budged!! I have tried turning it to break it loose, I have made a tool using a 1/2 inch grade 8 bolt to try and press it out after letting it soak two nights with high quality penetrating oil. I would like to drill it out, but we are talking 3 1/2" of free hand drilling and as good as my partner is doing machine work, we have not used that last resort. Anybody got any ideals? If I could get the car on a roll back without damaging it, I would make the 2 1/2 hour trip to Fatmans and let his guys have some of the hair of the dog's back!!

Trees
 
#24 ·
everone, lets meet at Trees'

We'll get you loaded, and even make the trip with you.
wonder what a shop would think if 35+ people showed up to raise cain over sumptin'?

I can't see what your lookin' at, but i don't guess theres any way to get a hammer on it, or would driving it out cause as much damage or more than you have allready?tth.
 
#25 ·
Well, when I have a stubborn bolt I always resort to heat. If you can get it red hot, it will loosen right up. I'm with 4jaw on the grade 5/grade 8 issue. Grade 8 is better in every way, tension, shear, torsion, etc. Factory hardware are all forgings or grade 8 equivalent bolts. In fact the bolts may even be forgings. I still would look for a way to pick up the bending stress on that lower A-arm with something like a strut rod like the added bracket on the one I reference above. Just too much going on down there to be without that extra insurance for my liking.
 
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