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While disassembly a new-to-me 1973 GTV I found what looks like polyurethane t-bar thrust washer position fitting on either side of the bushes. Not one each side, but two on each side. They are severely deformed.

The image below (not my car) has arrows point to the where the washers were located on my car

I haven't seen this before except in this one image I found on BAT. I also couldn't find this part in the parts' manual illustration and none of the three parts distributors I contacted said they sell such a washer for this purpose.

Is there any reason for these washers to be where they were? Is it something done for track cars?

Related questions: how tight are the nuts to be tightened on the bolt that passes through the trailing arm and the bush? (So the arm deflects and touches the steel sleeve in the bush?) What if anything rotates or moves on this end of the trailing arm?

1647695


1647696
 

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Discussion Starter #3
Thanks for the reply. So there is a benefit to having them there?
And I should reinstall them?
 

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Some poly bushings use poly washers in that location.
 
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Some poly bushings use poly washers in that location.
I'd guess that's because the poly isn't bonded to the center sleeve or the trailing arm, and could thus allow the arm to slide back and forth? With a standard bonded rubber bushing that can't happen, and that washer wouldn't seem to do much at all (though I guess it would limit trailing arm twist somewhat).

From my '91 manual the nut attaching the trailing arm to the rear axle is 79.7-98.1 ft-lb and the sway bar nut to the axle is 23.6-25.1 ft-lb. Trailing arm to body is 59-72.3 ft-lb. All should be tightened with the car's weight on the axle.
 

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Discussion Starter #6
Thank you Tom for torque specs and others for the possible reasons they are on this car.
 

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if your bushings are OEM style rubber, those thrust washers do not go there.
if your trailing arm bushings are poly - those thrust washers do go there, and they usually do get pretty messed up on install.
the oem bushings are pressed into the mount tube and are locked in place by friction (a lot of friction) so they do not move side to side. the mount brackets have a short tubular center section that catches the bush bolt tube (on both sides) and clamps the whole assembly in place.
the poly pieces are pressed into the mount tube as well, but not a super duper friction fit like the oem steel bush jacket. soooo, the arms can slip side to side...or vice versa. the bush kits include poly thrust washers which are slipped over the short tubular centers on the brackets, taking up all the space between the bracket and the trailing arm bush... thus eliminating any room for side to side movement, locking everything in place.... thrust washers. is a snug fit as it should be, and when installing the trailing arms in place, there is lots of drag on the thrust washers.... causing them to get ugly. once all done, is all snug like bug in rug and never have to think about it again. trailing arm should tighten up nicely onto the mounting bolts.
there are thrust washers (bigger OD & thicker) for the trunnion arm/body joint. check the trunnion arm to see if IT has thrust washers. the vast majority of these cars are missing them. most owners do not even know something is missing. not sure how... if they are missing, makes for some scary handling. put them back in and the car becomes linear and direct... w no rear end self steering.

nuts securing the forward end of trailing arm 73>83 lb ft. nuts securing trailing arm to axle tube, 83>94 lb ft. they are big *** bolts. w oem style bush, tighten w car on ground. poly parts still best, but not critical, will self adjust.

What if anything rotates or moves on this end of the trailing arm? the simple answer is that none of these parts are supposed to move relative tot he car. is not an articulated joint like a ball joint or tie rod end.
w OEM style components, nothing moves or rotates at all here. the rubber inside the bush will stretch/compress/twist but it is bonded to the bolt tube and outer shell, so no motion relative to the car. the poly part will rotate inside the arm, but slightly. the supplied install grease takes care of that.
 

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A problem I see and have experienced is that the OEM type bushes isolate the trailing arms from the mounting points, as I see it having the washer type bushes installed is that any vibration and noise are then transferred to the body, usually not an issue at lower speeds in my case less than 70 mph, above 70, I had all kinds of noise, (not pleasant). Noise went away after replacing the trailing arm bushes with the OEM type. There are many threads linked to this issue, perhaps not all poly bushes exhibit this, Alfaparticle has stated he has no issues with his, but there are many that have complained of the unwanted noise. Just my two cents.
 

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if your bushings are OEM style rubber, those thrust washers do not go there.
if your trailing arm bushings are poly - those thrust washers do go there, and they usually do get pretty messed up on install.
the oem bushings are pressed into the mount tube and are locked in place by friction (a lot of friction) so they do not move side to side. the mount brackets have a short tubular center section that catches the bush bolt tube (on both sides) and clamps the whole assembly in place.
the poly pieces are pressed into the mount tube as well, but not a super duper friction fit like the oem steel bush jacket. soooo, the arms can slip side to side...or vice versa. the bush kits include poly thrust washers which are slipped over the short tubular centers on the brackets, taking up all the space between the bracket and the trailing arm bush... thus eliminating any room for side to side movement, locking everything in place.... thrust washers. is a snug fit as it should be, and when installing the trailing arms in place, there is lots of drag on the thrust washers.... causing them to get ugly. once all done, is all snug like bug in rug and never have to think about it again. trailing arm should tighten up nicely onto the mounting bolts.
there are thrust washers (bigger OD & thicker) for the trunnion arm/body joint. check the trunnion arm to see if IT has thrust washers. the vast majority of these cars are missing them. most owners do not even know something is missing. not sure how... if they are missing, makes for some scary handling. put them back in and the car becomes linear and direct... w no rear end self steering.

nuts securing the forward end of trailing arm 73>83 lb ft. nuts securing trailing arm to axle tube, 83>94 lb ft. they are big *** bolts. w oem style bush, tighten w car on ground. poly parts still best, but not critical, will self adjust.

What if anything rotates or moves on this end of the trailing arm? the simple answer is that none of these parts are supposed to move relative tot he car. is not an articulated joint like a ball joint or tie rod end.
w OEM style components, nothing moves or rotates at all here. the rubber inside the bush will stretch/compress/twist but it is bonded to the bolt tube and outer shell, so no motion relative to the car. the poly part will rotate inside the arm, but slightly. the supplied install grease takes care of that.
i found that not letting the rear axle rotate as to the body will lift a inside tire, leading to snap oversteer...on my 84, i have instaled spercial bearing on a set of extra trailing arms.. this will allow the rear axle to stay on the road longer as it would let the rear axle rotate to the road as compaired to the bodyshell
 

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The 105 C-shaped trailing arms are designed to twist when the car leans into a corner. They effectively offer some degree of roll resistance. Increasing the bushing stiffness will also increase this contribution to roll resistance. Indeed, pushing a car with a soft suspension and a rear sway bar into a corner will lift the inside wheel.

The Giulietta trailing arms were tubular thus much stiffer. With the car leaning into a corner, the tube won't twist much; only the bushings can accommodate the roll movement of. the body relative to the axle. In extreme cases, the brackets will twist. Giulietta trailing arms brackets on the axle have been known to distort and fail, especially when racing. This can be lethal. Stiffer bushings should be absolutely avoided on a Giulietta that doesn't have a race suspension.
 

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In my experience, for all except the hardest core street performance desires, and track cars, a quality OE rubber bushing for the trailing arms, performs better than the Poly bushings. Most complaints about the OE rubber, is because they are old, and worn out. These bushings must be indexed to proper ride height before the through bolts are tightened. Failure to properly index the bushings, is one reason that they perform badly, and wear prematurely.
 
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one thing you should consider, the poly trailing arm bushings (well, the ones i sell - performatek.com) are of roughly same hardness of the rubber ones. generally, they are a few points firmer, but not some exponential jump in firmness. there behavior is much like the rubber pieces they replace. they are easier to install and last a lot longer than the rubber pieces. just aayin'.
 
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