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1968 AMX Front Trunnion Elimination |
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amx39068
Supporter of TheAMCForum Joined: Feb/21/2008 Location: Arizona Status: Offline Points: 11576 |
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Almost forgot to add, the car we welded up the bushing socket on is a 70 AMX that is getting new rubber bushings rather than urethane. The car is being restored for a guy who wants it for his wife to drive to stock shows with him in his killer Packard. We decided that ride comfort will no doubt be a priority over handling so the car is getting rubber bushings all around and original passenger style white latter tires just like AMC did it.
Edited by amx39068 - Jan/11/2013 at 7:49am |
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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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uncljohn
AMC Addicted Joined: Jan/03/2013 Location: Peoria AZ Status: Offline Points: 5394 |
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My contention is and remains, the lower control arm is a weak spot in the Existing AMC front suspension as to it's operation and reliability.
What ever else one does to them is pretty much personal opinion. Mine is, urethane bushings aggravate the inherent weakness of the design. Stiffness is not an attribute, it is a preference. And stifness does not solve design problem. Arguing it is a positive attribute is a lost cause, it is an opinion. And not mine. However in either case AMC designed the lower control arm to flex in order for it to do it's job more or less and my experience in working on them the mechanical failure rate is high as a function of time and miles. Trying to eliminate flexing aggravates binding. I've done my home work and research to verify that. For what ever that is worth. ' This comment excerpted from an article on the Chris Alston designed Pinto or Mustang II suspension in terms of improving on the original design by including a free standing lower control arm to eliminate the strut rod and pivot point, and inherent problem in that suspension which needed to be solved also as it is similar if not identical in operation to the AMC control arm indicates the same piece of information needed to be taken care of. By redesigning the lower control arm into an A-arm design and incorporating a new rear mounting point that rotated on the same axis as the forward pivot, Alston eliminated the inherent binding experienced with stock-type components caused by the two off-axis pivots. I have made my decision how to deal with the situation as I see it. And A stack of damaged lower control arms is a significant factor in making it. The information is there for others to see and use as they see fit. But again using urethane because it makes things stiffer, is not a solution. In fact in certain instances, it is part of the problem. There is apparently currently available only one option to replace the existing AMC suspension with a modern equivalent and with the associated benefits. Admittedly a tad pricey but it is one more than none. And is probably worth every dime spent on it if you want it. And if that works for some people the option is there. It is not a Rambler mentality decision to use or not use it as was narrowly pointed out. It is one of evaluating need vs expense and then making an educated decision. The more knowledge that is available the better the decisions can be. Doing something for cheap rarely gives the best solution. Neither does arbitrary throwing money at things. After all the U.S. did not get billions of dollars in debt by making financially smart decisions. |
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70 390 5spd Donohue
74 Hornet In restoration 76 Hornet, 5.7L Mercury Marine Power 80 Fuel Injected I6 Spirit 74 232 I-6, 4bbl, 270HL Isky Cam |
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tyrodtom
AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6214 |
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A lot of 4 cyl. circle track cars have a similiar design lower strut rod, some behind the lower arm, some ahead. When rules allow it, some replace the sleeve bushing with a heim rod ends. They let the suspension go thru much more range of motion without binding. I talking race track, we're not concerned with road noise being transferred back thru the suspension mounts.
I done this myself to a few cars, and looked at my 66 American's strut rod and think I might try that on it.
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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THE MENACE
AMC Addicted Joined: Nov/04/2008 Location: So. California Status: Offline Points: 4438 |
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Something like this maybe?
This strut rod eliminates 100% of the bind and will not twist the lower control arm (like a stock strut rod does) as the front suspension goes through it's travel. It's also much easier to adjust than a stock strut rod!
Dennis
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Former Owner of:
The Craig Breedlove "AERO AMX" Still Owner: SS/AMX #9 replica (THE BIG MENACE) 70 AMX 416, EFI, Nash 5 speed 70 Javelin 401, 727 (Wife's car) 72 Gremlin Autocross Project. |
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tyrodtom
AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6214 |
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Like that, but i've done it by welding threaded rod to the stock suspension arm and installing the heim joint on that.
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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JonnyB
AMC Apprentice Joined: Nov/26/2012 Location: Indianapolis Status: Offline Points: 51 |
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I've looked into replacing my trunions too, I'm going to use a knuckle from something non-trunion and make an upper arm, I think Howe sells a kit if you would prefer a kit, but I plan to just use tubing, heims, and some plate...
There is NO WAY I would pay that kind of $$$ either, esp. when you can make it yourself... |
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Buzzman72
AMC Addicted Joined: Sep/15/2009 Location: Southern IN Status: Offline Points: 2726 |
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I've often had the "fantasy" of taking a pre-'70 AMC body and swapping in the entire front frame rails and inner fenders of a '70-up body. Such as a Hornet/Gremlin clip on an American, or my favorite, a '70-up Ambo clip on a '67 Marlin. Sure, the upper "troughs" might have to be swapped from the old to the new, in order to be able to bolt up the fenders. And YEAH, having the measuring system from a quality frame rack would probably make the job a ton easier; easiest yet would be to have your own frame shop out back.
But the trials and tribulations of the trunnion front end on the '68 Jav I once owned have me totally sworn off trunnion suspensions for life...unless I can win the lottery and buy the '56 Hornet Special Hollywood Hardtop I have my eye on. THAT one, I'd keep as-is.
Edited by Buzzman72 - Jan/11/2013 at 9:58pm |
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Buzzman72...void where prohibited, your mileage may vary, objects in mirror may be closer than they appear, and alcohol may intensify any side effects.
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19692 |
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You only have to change the spring towers to use the upper arm and spring from a 70+ car in a 68-69. The Hornet/Gremlin spring tower will work in the 68-69 Javelin AMX with a little tweaking. This is a lot of work though, lots of spot welds to drill out. I'd rebuild the upper trunnions (or get rebuilt ones). Costs less in the long run, and can be installed in a day if you have the spring tools. Car will handle great with the urethane trunnions too.
The only thing you gain is the ability to dial in more positive caster by changing. As John says, you can only get 3 degrees in the trunnion suspension before it starts to bind -- he's saying the ball joint suspension does the same, I believe. I have 3 degrees in mine now and it wants to wander a bit, as John also mentioned. This is on a 112" wheelbase Classic wagon though, not a short wheelbase AMX or Gremlin. I'm going to have it set at 0 degrees when I have it aligned next and see if anything changes. I agree with John on the flexing of the lower arm, trunnion or ball joint suspension. It was designed to flex. If the inner bushing on the lower arm is urethane it is more resistant to twist and the arm itself must twist more and the suspension movement is hampered. I don't use urethane strut rod bushings. In my car I can feel a pot hole jar in the floor when I did. Half as much with rubber. I'm not sure the urethane bushing stresses the arm a lot more, because the whole suspension doesn't move as much. The harder urethane will bind more, restricting movement slightly. Modern smooth roads, radial tires, and good gas shocks mean the suspension doesn't HAVE to move as freely as it did in the 60s with rougher roads, harder tires, and stiffer shocks. So as Dan says, it's about full circle and doesn't matter as much. Rubber will ride a bit smoother, and good new rubber will handle just about as good as poly. Poly holds up longer though -- 10 year old rubber won't handle as good as 10 year old poly. Don't use NOS rubber, use new! NOS is still old and may be dry rotted -- won't hold up long. Should be okay for a seldom driven show car, but the NOS strut bushings I tried about 10 years ago disintegrated after a few months of driving. I have rubber suspension bushings with urethane sway bar bushings. For performance I've recommended "half-n-half" strut bushings -- urethane in front, rubber in back. Urethane isn't as soft and flexible as rubber, and the strut bushings restrict up and down movement a bit. The hard bushing in the front prevents caster changes on acceleration, the rubber in back allows a bit more and faster movement. Not so concerned about caster changes backing up! Edited by farna - Jan/12/2013 at 1:42pm |
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Frank Swygert
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husker
AMC Apprentice Joined: Sep/20/2012 Location: Mooresville, NC Status: Offline Points: 33 |
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I am putting together parts to rubuild my trunions and had a question:
AMX39068 states that the thurst bearing i.d. is 1", but looking at:
http://www.skidmore.edu/~pdwyer/amc/trunnion.htm#parts - http://www.skidmore.edu/~pdwyer/amc/trunnion.htm#parts
it states to use a Nice 608v which is a 7/8 i.d. thrust bearing. Just want to make sure before I order the parts.
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0069X
AMC Addicted Joined: Oct/08/2008 Location: Akron, Ohio Status: Offline Points: 1725 |
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I've never had any complaints with my trunion suspension, but all I ever hear is CONTROL FREAK. So just how expensive is it for a 69 AMX?
Edited by 0069X - Jan/22/2013 at 8:45pm |
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