TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > Suspension, Steering, Brakes & Wheels
  New Posts New Posts RSS Feed - 1968 AMX Front Trunnion Elimination
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

1968 AMX Front Trunnion Elimination

 Post Reply Post Reply Page  <1234 6>
Author
Message
amx39068 View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Feb/21/2008
Location: Arizona
Status: Offline
Points: 11576
Post Options Post Options   Thanks (0) Thanks(0)   Quote amx39068 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 9:56am
Sorry John but I strongly disagree with your assessment. As you know, many of us within our club only use urethane and NONE of us have any of the issue you are describing nor have we worn out parts from using urethane bushings despite driving our cars all the time. On the other hand, improper installation of any part, including rubber AND urethane bushings, will cause the type of issues you describe.

I have seen many AMC suspension parts worn out due to the rubber bushings breaking down and resulting in metal to metal contact which coincidentally is the prime reason why trunnions wear out and cannot be rebuilt. Contrarily and despite using urethane now for nearly 20 years, I have NEVER seen an AMC suspension part worn out from a urethane bushing. I have also seen many rubber bushing housings tacked to control arms so that is not an issue that should be associated with urethane.

There are two schools of thought within the AMC hobby, one being that we MUST leave the cars the way AMC built them because they were designed that way and the other being that 40-50 years worth of technical advancements are available and we should use those advances to make our cars better. I think it is clear which side the two of us are on.

And I always get a kick out of those who insist that things don't work properly despite clear and indisputable examples to the contrary. I use urethane because I both believe and have first hand experience on multiple cars that they ride and handle far better than the rubber bushings. Admittedly I have a personal preference for the ride that the tighter urethane bushings produce over the softer rubber bushings but properly installed urethane bushings are an excellent and inexpensive way to upgrade the ride (my opinion of what a performance car should ride like - others do not agree) and handling of our cars.
Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
Back to Top
husker View Drop Down
AMC Apprentice
AMC Apprentice


Joined: Sep/20/2012
Location: Mooresville, NC
Status: Offline
Points: 33
Post Options Post Options   Thanks (0) Thanks(0)   Quote husker Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 10:22am
What urethane kit do you suggest?  I was looking at the Prothane kit. 
 
Do you have a part number for the thrust bearing?
 
Thanks
Back to Top
uncljohn View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/03/2013
Location: Peoria AZ
Status: Offline
Points: 5394
Post Options Post Options   Thanks (0) Thanks(0)   Quote uncljohn Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 11:17am
Preference or not is beside the point and whether you disagree or not is not a concern to me. The fact remains the lower control arm is a weak point due the way it is designed and works and urethane aggravates the failure mode.  And ride preference does not change the inherent weakness of the design.
That said, what you do is your decision. Not mine and I really don't care. Simply because my first hand experience which is also extensive is to the contrary. Which as far as I am concerned is both clear and indisputable.
Generally metal to metal contact is a function of neglect when it comes to maintenance as applied to proper care.  This could be easily seen when prowling wrecking yards looking at worn out front suspension for core parts.  These are cars that quickly became beater status once the new wore off to where repairing them became a financial burden that exceeded the cost of buying a replacement.  I have yet to see one that was not badly worn but that is a whole nother story.
So the nice thing about your disagreeing with my easement I on the other hand, disagree with yours.

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
Back to Top
Wrambler View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/02/2007
Location: West Virginia
Status: Offline
Points: 4197
Post Options Post Options   Thanks (0) Thanks(0)   Quote Wrambler Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 11:40am
Originally posted by uncljohn uncljohn wrote:


SNIP
That said, what you do is your decision.
Not mine and I really don't care.
SNIP.



You are correct it is our decision.
I have run Poly on my car in WV on crappy roads for years. No problems at all. Yes I do know how to check for the problems you mention, installed and lubed correctly they simply are not to be found on my car.

The length of your posts implies you really do care.



Edited by Wrambler - Jan/10/2013 at 11:40am
Wrambler
69 AMC Rambler
4.0L, 5 speed
2015 Grand Cherokee Limited
2019 Chrysler 300
Back to Top
amx39068 View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Feb/21/2008
Location: Arizona
Status: Offline
Points: 11576
Post Options Post Options   Thanks (0) Thanks(0)   Quote amx39068 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 4:19pm
We only use Prothane. If you order them from the internet be sure to specify black unless you really want bright red (if you do I will give you a great deal on a set of reds ones :-). When removing the old bushings be sure to put a spacer in between the two sections of the control arms when you press them out or you wll crush the end of the arm where the bushigns go through. Also, be mindful that you need to reuse the outer shell of the old bushing as the prothane bushings only come with the inner sleve due to the urethane bushing not containing the outer shell. Also be sure to use plenty of the bushing grease on any surface that contacts another surfare particularly the inner sleeve surace inside the bushing.

I don't have the bearing part number with me but they are 1" ID thrust bearings. When you speak with a bearing supplier be sure to tell him its a thrust bearing otherwise you might end up with a skate board bearing!    
Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
Back to Top
69 ambassador 390 View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Nov/22/2009
Location: Peoria, AZ
Status: Offline
Points: 3539
Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 9:17pm
I just pulled a number of stock rubber "INSERTS" out of the stock shells both today and in the very recent past.  This includes some NOS bushings that had never been on a car.  I did this to install poly inserts in the original shells.  The thing is, not one single rubber insert was "Vulcanised" to the shell.  They all push out very easily with the correct size washer and a bolt.  They are not vulcanised to the shell as was said.  They are very tight and don't move in the shell though.  All the shells came out shiney clean with no rubber left at all.  Secondly,  I had poly bushings in my Ambo for well over 200,000 miles and never had a crack or broken part that could be attributed to the poly.  I did have a strut rod fail at the spot where the threads ended on the shaft after hitting a huge pot hole in sub zero temps.  I can't blame that on ploy though.  More like 150,000 miles on a 30 year old car.  The trunnion suspension was always completely trouble free if adjusted correctly and kept lubricated.  I know the big car is different but basically the same idea.  The advent of ball joints was not brought about by the design being better but because it used fewer and cheaper parts.   Although I preffer the softer ride of rubber on a cruiser I can truthfully say that my big car handled a lot better with the poly.  There was more than enough adjustability in the stock suspension to make up for the radial tires and, at least on the later big cars, you can put cam bolts on both the upper and the lower arms.  The early cars had the cam bolts on both uppers and the later ones on the lowers.  By switching to all six cam bolts, the adjustability is nearl infinate.  It's a simple mod.  A final note is that if installed correctly, most poly lower strut rod sets are of a ball and socket style and they can articulate quite a bit while still controlling fore and aft movement of the control arm.  The tacking that was mentioned is a very common fix for arms that have had more than one set of bushing shells installed during their lifetime.  It is always done on the non-lipped wall of the control arm that often gets a little oversised.  I do it as a matter of course just for insurance.  Did two today that had nothing to do with poly bushings.  They were virgin AMC rubber all the way.  I usually use PST polyGraphite bushings myself because they are resistant to squeaks due to the impregnated graphite in the compound.  The ProThane are nice also.  There are legitimate reasons for both styles bushings depending on user prefference but not because of scare tactics involving part failures.  Those are most often installer error or incorrect tool usage.  Use what you want and don't be afraid of either choice due to fatigue falure issues.  You are more likely to hurt the arms pushing in and out stock rubber style bushings than to leave the shells in place and use poly inserts.
Steve Brown

Algonac, Mi.

69 Ambassador sst 390

84 Grand Wagoneer

69 Cougar XR7

65 Fairlaine 500XL

79 F-350 Super Camper Special



Back to Top
uncljohn View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/03/2013
Location: Peoria AZ
Status: Offline
Points: 5394
Post Options Post Options   Thanks (0) Thanks(0)   Quote uncljohn Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 11:28pm
Ive never seen Cam Bolts on any of the 70 + suspensions I have either rebuilt or torn down for parts. If they are there they don't show up in the TSM's either. And I have built a number of them and salvaged parts on more.
Other than Trunions work when they are built correctly personally I don't like them. But that is a preference not a judgement on their functionality other than, there is no Anti-nose dive geometry on a Trunion equipped car. There is on one with ball joints.
And my concern is the operation of the lower control arm. The way it moves to support the suspension motion is in a compound arc and the lower control arm is designed to flex when doing so. And when the front suspension is adjusted for positive caster which favors the use of Radial tires the flex is aggravated.
Proper function expects the lower control arm to flex along with the bushing which does so because it is rubber.
In rebuilding them and obtaining cores I would estimate that about of third of them were damaged beyond being re-usable. I still have a stack of upper control arms but I am down to welding up lower ones and re-finishing them. And yes I care that it is understood how that suspension actually works.
But what one does with it is frankly not a concern of mine.
I like that (I forgot the name of the suspension piece referenced) it is worth the 4 grand it costs for what you get. A whole new front cross member, tubular triangulated control arms, modern disc brakes and rotors. Rack and pinion steering! I guess from what I read Power is Coming. Flaming River already has it so it can not be too far behind. It yanks an AMC car out of the dark ages and into the modern world in front suspension technology. But if you are going to spend 4 grand on suspension the odds are you are spending a whole lot more on the car. It ain't gonna be a beater and certainly not a restoration.  There are few AMC cars worth spending that amount of money on as an investment for restoration that can absorb a major non stock front end and still have people ready to spend deep pocket money on them.
Then again looking at the rest of  car.  A stiffly sprung car to utilize the benefits of being stiffly sprung needs a solid body to bolt things to and AMC is not that.
My Spirit with a 100 inch wheel base and an Arizona car thus no rust has more body flex than my Chrysler van does, a 2007 which also handles better.
An AMC car is a toy and fun to own. I have built more than a few and enjoyed everyone of them. Most of them are not worth squat financially but on the open road they draw attention, and will run well.
And re-engined run even better.
My Hornet Sportabout is one of those things. I'll end up spending close to 2 grand when the upholstery is done. But it will be righteous when completed.
 Some of them are actually collectable. But things like rubber bushings? I have yet to see one that was not vulcanized to the shell, but they are old and don't take much effort to press them apart. I had two Old Stock strut rod bushing sets purchased through Kanter. I installed them on my Hornet sitting on jack stand. Both sets failed completely in 3 weeks. I bought new moog pieces. Why did they fail? New Old Stock means just exactly that 45 year old rubber dies.
The lower control arm is a throw back design and is problem prone. Treating it with care will keep further problems from happening. Installing urethane  is asking for failure. That is a design factoid. The question is not one of if, it is one of when.
Keep in mind, many of these things went many miles with minimum maintenance. That was what they were built to do for the most part. And they did it.
 As far as stiffness.
I am tired of things that ride like trucks unless they are one.
But that is a preference.'
I will walk away from one that rides that way at this point in my life.





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
Back to Top
69 ambassador 390 View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Nov/22/2009
Location: Peoria, AZ
Status: Offline
Points: 3539
Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2013 at 11:50pm
 We are talking a 1968 here.  That is stated in the original post.  I beleive Control Freek has a front tubular arm set up that bolts to the stock locations and is very reasonable.  That set up could be installed on the 68 for a low cost and leave the option for adding coil overs later.  The complete rack and pinnion front with coil overs does not have to be installed.  I now have the full Control freek coil over set up both front and rear but that is not all that they offer.  The stock lower arms are not designed to flex during travel but instead to follow a common sweeping motion folliowng the arc between the strut rod attaching point at the rear and the  lower bushing at the cross member.  You assertion that the arm should flex that much while supported by the triangulated strut rod doesn't jibe with all that I've learned or been tought in all my years working on suspensions.  Do you have any accepted industry litteriture to support that?  Never heard that claim before.  Fords used that same lower arm with triangulated strut for many years into the 1990s also.  Where did your info come from?

Edited by 69 ambassador 390 - Jan/10/2013 at 11:58pm
Steve Brown

Algonac, Mi.

69 Ambassador sst 390

84 Grand Wagoneer

69 Cougar XR7

65 Fairlaine 500XL

79 F-350 Super Camper Special



Back to Top
uncljohn View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/03/2013
Location: Peoria AZ
Status: Offline
Points: 5394
Post Options Post Options   Thanks (0) Thanks(0)   Quote uncljohn Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2013 at 6:27am
30 years of rebuilding these things and wondering why they are so badly tore up and working with people who fabricate front suspensions and modifying the Ford suspension so that it works with out going through the monkey motion action at the lower control arm.  Talking with people who seriously road race the cars and listening to the problems they  have had getting these suspensions to actually work competitively or competitively enough to function in today's world anyway.
Most of the after market solutions to the Pinto/Ford/Mustang II inherent problems is to come up with a tubular lower control arm.
And 68 or not, the problem is inherent in the lower control arm strut rod geometry as it controls the location of the lower control arm, it's pivot point and the stresses applied at it as caster is adjusted.
If control freak has bits and pieces that work, it is a function of using them if you wish to obtain a modern variation. The custom car culture uses any number of suspension variations all based on some kind of a cradle or another that bolts or welds onto the frame or becomes the frame. But each and every one of them have to be custom built to actually fit. Which apparently what the control freak does when looking at them to make them work with an AMC. The prices I see are pretty much in line with the industry at large. The question is whether some one wants to spend the price on one hand and once done, whether the end result, a modification is marketable to the next owner at that price.
And I guess in part that depends on what the next owner thinks they are buying. A valuable restification or a street rod.
For the most part, where I see the next owner paying value dollars is on a street rod if they are going to spend the money.
Most street rods change hands; routinely for far more than the same car restored does on the whole.
If the 68 has adjustable upper control arms it has no bearing on the geometry of the lower one. It's geometry for the most part is controlled by the positioning of the strut rod. The 70 and up caster is controlled specifically with the strut rod. An inexpensive application using the Ford derived pieces in suspension modifications requires re-bending of the strut rod to get the plane of motion in line with the pivot point and then making new strut rod mounts to support the thing.
While not commonly done, a good fabricator can fabricate the mounts and weld them into location and have them work.
Again, the AMC front end, designed before the universal use of radial tires was designed to work with in it's application, that of a family car rather than something with performance potential and was in it's day state of art, worked and performed it's job. The shift to ball joints was years after the industry had done so, before radial tires were popularly used and allowed the manufacturing of anti-dive braking geometry which required the steering knuckle to move in a manner the trunnious would not allow. So that was a plus.
Bias Ply tires have a whole different set of dynamics that take place where the rubber meets the road. To the extent today that in certain applications they have become a niche market product.

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
Back to Top
amx39068 View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Feb/21/2008
Location: Arizona
Status: Offline
Points: 11576
Post Options Post Options   Thanks (0) Thanks(0)   Quote amx39068 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2013 at 7:31am
This discussion has come full circle. The very reason many of us use urethane is because all passenger tires other than retro manufacturered tires are radials. Rubber mounts were an important element of the car's ride and handling with bias ply tires whereas radial tires by nature of their design and more shock abosorbing nature along with gas vs oil based shocks change the entire ride and handling characteristics of a car. Interestingly, one could legitimately argue that putting radial tires on a car with rubber bushings over compensates for the very issues that have been discussed here and therein lies the rub: What is actually the best combination for ride, handling and safety? There are no back to back tests or engineering analysis of the two combinations so everything posted arguing both sides is mere speculation

One thing is for certain however and that is NONE of my cars ride like a truck and in fact ride AND handle like a modern car while still providing a supple ride that is not harsh yet much firmer than the stock rubber bushings in combination with radial tires. Suggesting otherwise is merely the result of someone not having ridden in a car with urethane bushings that is set up properly and with good gas shocks. Many, many AMCs are set up with a hodgepodge of suspension parts. On the other hand, we have researched, tested and validated the setups we use and have a list of proponents who are not only satisfied with the setup but no longer consider using anything else. Like anything in life, it all boils down to personal preference but suggesting that there are dire consequences of going one way or the other is simply not true. We are talking about 40 year old cars here. Things break and just yesterday we had to weld up an upper bushing socket that was cracked with (you guessed it) original style rubber bushings. It happens.

Edited by amx39068 - Jan/11/2013 at 7:32am
Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
Back to Top
 Post Reply Post Reply Page  <1234 6>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.234 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or