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sjaakslinger 
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Joined: Jan/05/2011 Location: The Netherlands Status: Offline Points: 276 |
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 Topic: trunnion questionPosted: Jan/10/2021 at 12:43pm |
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Front suspension question. We replaced all bushings (among other things) on my 65 Marlin and are now installing the upper arm (A-arm). We reinstalled the trunnions by using a handy guide that can be found online. Upon imitating the realistic movement of the trunnion, one trunnion cap rotates along with the trunnion. So it rotates in relation to the control arm. Is this ok? On the other side of the same arm and on the other side of the car, the trunnion caps stay in place in relation to the arm. Tightening the cap with it's weird half thread doesn't help. Thanks. Dennis
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First_Gear
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Joined: Jan/18/2010 Location: Mukilteo WA Status: Offline Points: 644 |
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Posted: Jan/10/2021 at 1:28pm |
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No this is not ok. The caps are supposed to be one with the arms and should NOT turn. It sounds like it is binding.
Read TomJ's write up on the subject: https://www.sr-ix.com/AMC/Suspension-1962-1967-big/index.html. The joint should turn smoothly and not bind. If the caps are loose in the arm all is not lost just tack weld it in place to keep it from turning. I used the green locktite retaining compound when I put mine in to keep them in the arm but it was a very tight fit so I can't imagine them backing out.
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sjaakslinger
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Posted: Jan/10/2021 at 2:29pm |
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Thanks. Yeah, I used TomJ's great description, but he only mentions tightening the caps by hand. That made me wonder if they should stay in place or not.
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tomj
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Posted: Jan/10/2021 at 11:04pm |
Simply a forgotten step -- tighten the trunnion caps into the arms. I could not locate a torque spec, but given the weird likely-self-tapping nature of the thing I wouldn't much go by size (large). 25 ft/lbs? Or "tight as can be without deforming the metal where the flats meet the metal". Dunno how well-calibrated your arm is. You definitely do not want to crank down on it (or any!) fastener "as hard as you can". Lug nuts, big suspension bolts, a few engine internals are all that get big torque, mostly, 60 ft/lbs plus and minus. Those will all be grade 8 and large. Rear axle nuts, 300 ft/lbs, 18" breaker bar, extention on a jack stand, me at 150 lbs standing on the end. For comparison purposes, this is "a lot" of torque and would strip out the caps for sure. Without a torque wrench we're just waving our arms around... lol |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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sjaakslinger
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Joined: Jan/05/2011 Location: The Netherlands Status: Offline Points: 276 |
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Posted: Jan/12/2021 at 1:08pm |
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Thanks. Also for the great description you put online. I put some loctite in, letting it dry first. Really have some hard time getting one trunnion in correctly. One twist and it's too right on one side of the trunnion, one twist back and the distance between the arms is too big.
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tomj
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Posted: Jan/12/2021 at 11:10pm |
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"tight on one side of the trunnion" I don't understand what you mean... if the gap is right to get the spacer in correctly, then hold the arms as-is, and rotate the trunnion itself to center it.
Posting photos would be a big help. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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sjaakslinger
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Joined: Jan/05/2011 Location: The Netherlands Status: Offline Points: 276 |
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Posted: Jan/17/2021 at 7:36am |
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Sorry about that. No pictures at hand right now. I used your step-by-step. One trunnion cap hand-tight first into the arm. Then thread the trunnion in the cap. Then the other arm on the other side of the trunnion till it couldn't go any further on the trunnion. Then came the issue: Either the gap for the spacer was too large, or the gap was just right, but resulting in a trunnion cap coming loose (due to this design with trunnion threading into the cap and the cap threading into the arm). All the time checking if the trunnion could freely move in the caps exactly as it would in the car....
Hopefully this is a little clearer. I could take pictures later this week. For now I've loosened the cap a little in order to have the trunnion turn and put loctite in. I think there's no way it would come off, even without loctite. The thread on the cap and arm is pretty rough, the cap is hard to take off by hand. Even with a tool.
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First_Gear
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Posted: Jan/17/2021 at 11:50am |
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I think maybe I understand your mistake. You are adjusting the gap by loosening the caps? This is not correct. First the trunnion must be completely disassembled. The spring perch unscrews. I used a vice grip to remove it. The nut inside must be removed and the spindle taken off. Then you put the spacer into the arm and tighten to the spec. It should fit in there just right. Not too tight not too loose. If its not correct you take the arm half and unscrew it one rotation NOT loosen the caps. The final step if the trunnion is closer to one arm half than the other simply grab the little trunnion cross and rotate it until it is in the center.
It also occurred to me that you could have the arm halves backwards. The caps screw onto the side with the little lip not the side where it is flush with the arm. |
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tomj
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Posted: Jan/18/2021 at 12:33am |
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What First_Gear says. It sounds like you're getting hung up on being too literal with my poor choice of words.
Put the caps into the arms, and tighten them. I tend to be increment and go slow. I will edit the page this week. Just install the caps, tighten to final torque ("tight" but don't strip), done and done. THe main thrust of the page is this: just screw the center trunnion casting -- with the spring perch, knuckle, everything removed -- into one arm half. "all the way" but it's not anything really specific or critical; occupy most of the threads. (If you are left-handed like me) hold the just-assembled arm-half-plus-trunnion in your right hand, and now screw on the other arm (with it's cap installed). One, two, turns, lay it on the table. Set the spacer in the space where it goes (two holes lined up). There will be a giant gap because two turns isn't enough. Pick it up again, as before. Rotate the left arm one full turn. Put the assembly back on the table. The gap is smaller. Repeat until the spacer *just fits* in the gap. The far end of the arms, that has bushings that goes into the chassis, I think it's 8.25" between the tips, it's on the page. That the final check. If that doesn't work, something is wrong -- bent arms? Wrong spacer? Low quality phone photos would be a huge help. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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sjaakslinger
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Joined: Jan/05/2011 Location: The Netherlands Status: Offline Points: 276 |
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Posted: Jan/18/2021 at 8:58am |
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Thanks guys. Might be limited English language on my behalf. I think i do get the principle though, how the trunnion threads into the caps and the caps into the arms. And how the concept of the trunnion works.
It's just this. With one cap in place in the arm, the trunnion threaded all the way into the cap. Then the other arm threaded onto the trunnion. When I 'reach the point' where the spacer fits just about snug (resulting in the correct 8.25" between the tips), the trunnion can't make the slight back-and-forth movement as it would on the car. Not without slightly loosening one cap, because the slight rotatation of the trunnion makes it's thread reaching it's max within the cap. Don't know if this is understandable language.  Other way around: when taking the trunnion as a reference, having it threaded into the caps just about far enough to still make the movement as if on the car, I have both arms pointing in 180 degrees opposite. I tried everything to get it right. It's either as in my first description in this message (trunnion tight and loosening 1 cap) or as in my last description (trunnion correct in movement, but arms pointing opposite). Tomorrow is car-hobby-day, so pics will follow tomorrow... Oh yeah, arms got blasted and re-painted. Maybe that changed the whole geometry or something.
Edited by sjaakslinger - Jan/18/2021 at 9:00am |
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sjaakslinger wrote: