Re: [Amc-list] American trunnion (58-63 type)

[Tom Jennings <tomj@xxxxxxx>]

On Mon, 2007-07-02 at 00:13 +0000, farna@xxxxxxx wrote:

> Tom, I think you give up to easy! 

Nahh, I'll give up only if the part is ruined from more and more extreme
attempts at extraction :-) Tomorrow I go to the machine tool store and
see what the have for HARD bits. Carbide, etc. I'll get advice, if not a
tool. Then I'll order something from MSC.

That doesn't look like a standard thread, it almost looks ACME-ish.

I was able to clamp it well with a hold-down kit on the mill, those cast
flats do just fine.

I don't know how the hell you were able to hacksaw yours, mine is hard
as a rock. Sawblade (Starett brand steel) slips over it like greased
watermelon. Doesn't even make a shiny spot! Same with HS steel drill
bit, I went slow, use lots of oil, then harder to see if I could cut
surface hardening etc. I did use a bit from my cheap chinese crap bit
set. From the store I'll bring home a big gun (carbide etc).

Actually, the last resort would be the "tap disintegrator" approach. For
$150 they'll get the POS outa the damn hole! It's still cheaper than
outright replacement.

(I think the trick is to mill a grease groove into the casting, and not
mess with the bolt thing. But not weaken the thing.)







> I repaired mine years ago. I didn't have much choice, so I got it done. Instead of a drill bit you might try a carbide cutting tool. Or a carbide tipped bit. You know, I'm probing the deep reaches of memory (I repaired my worst 63 upper trunnion about... 20 years ago??), but I seem to recall taking the trunnion to a machine shop to have that bolt drilled out becasuse of the same problem you're having. They used a drill press and carbide bit, I think. It's hard to say from 20 years ago! But I didn't have much luck with a standard drill bit. I do remember using a 9/16 bit, which is just over the size needed to thread a 5/8" hole. That gives the bolt a looer fit, leaving plenty room for grease to move around it and still enough thread to keep it in place (though the arms limit sideways movement anyway). I do know for sure I cut the arms off (cut the pin) with a hack saw. I might have used a blade for each cut (can't remember), but get a real goo
>  d blad
> e. Using a couple $5-6 blades just to make two cuts may sound expensive, but the alternative is a $175 or so replacement. 
> 
> I'm not sure if the camber is the same on the later models, but mounting isn't a problem. The inner bushings are different for arms that use a bolt to mount vs. the early American's mounting rod. You should be able to use the early bushings in late arms. I haven't tried it, but they appear to have the same outer diameter and profile. Should be easy to get those measurements. The mounting rod type have a larger inner diameter because the rod must be larger due to no support on one end wheras the bolt through type are supported on both sides.
> 
> Instead of going newer, try going older. The 50-55 Nash Rambler trunnion should be much cheaper and bolt on as easy (or easier) than a later model. In fact I know that the complete 50-55 front suspension will bolt right on. The steering knuckle of the earlier and later (than 58-63) suspension may have a different size/design pin on top (where it goes through the trunnion). That would be the real sticking point. 
> 
> 
> ----------------
> Date: Sat, 30 Jun 2007 14:41:28 -0700
> From: Tom Jennings <tomj@xxxxxxx>
> 
> Well I'm pretty much screwed. Another half dozen heat/soak cycles and it
> doesn't budge. Plus I drilled a hole in the casting in the middle to get
> Aerokroil in there. Did no good, and I sheared off my welded nut.
> 
> And that's on the one with enough stub that I can get a nut on it. The
> other one's sheared off -- both sides -- flush with the arms.
> 
> As a last resort I tried drilling them on my 1" capacity mill. The
> trunnion bolts are not much less hard than the drill bit; I didn't even
> get .25" in before I cooked the bit cherry red. I may look for some
> special super-hard bit but that seems desperate as a hole down the
> middle of a hard, frozen bolt may not help in this case; it's so long
> and no way to grip it.
> 
> Both trunnions have both arms stuck on there, which makes dealing with
> them difficult. 
> 
> With a good dozen hours in them I think it's safe to say they are
> unusable. With replacement costs over $700 for rebuilt used parts I have
> to find another solution. (I need arms too, so it'll be even more.)
> 
> Any ideas anyone? This kinda puts the car off the road.
> 
> Does a 64-69 upper trunnion system fit, or nearly so? It appears (from
> the parts catalog drawings) to have the right camber and it's probably
> the same upper bearing. But I think the arms fit into the chassis like
> all other 64-up cars, instead of onto that bolt-on pivot bar.
> 
> 
> --
> Frank Swygert
> Publisher, "American Motors Cars" 
> Magazine (AMC)
> For all AMC enthusiasts
> http://farna.home.att.net/AMC.html
> (free download available!)

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