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Discussion Starter · #1 ·
I dropped the trunion on my 73 GTV and failed to note which side had the slightly thicker trunion to body shim. I realize there might not be a definitive answer for this, but if everyone says the thicker one was on x side on their car... i'll have a pretty good guess.

I'm 99% sure the trunion has never been dropped before...

Thanks
 

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As far as I recall, there wasnt any side for the thicker or the thinner one. It depends what exactly needed at the factory. So, maybe were the same or different in thickness. This means that you need to measure the gaps in both sides so to drop the correct one.
 

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Different size shims were used at the factory to center the axil in the body. The only way now to get it right is to install the shims and measure to see if the axil is centered.
If not, switch them.
 

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Discussion Starter · #4 ·
Different size shims were used at the factory to center the axil in the body. The only way now to get it right is to install the shims and measure to see if the axil is centered.
If not, switch them.
Fair nuf.

How is the measurement taken?

I have the diff/axles off the car. Is there a way to do this measurement with the trunion alone or do I need to get the axle on there?
 

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RMM-
Since the position of the trunnion is relatively fixed in relationship to the body/frame by the position of the bolt on the diff pumpkin, and the ends of the axles are fixed in relation to the car by the swing arms, I would be willing to bet that you could swing the trunnion into place, bolt it loosely to the pumpkin, and determine which spacer goes on which side by trying to put them into the slots between the trunnion and the body. One will fit loosely on both sides and one will be too wide for one side.

I'm willing to bet that was how it was done at the factory.... taking Mohammed to the mountain, rather than by measuring the distance to the mountain. I envision Enrico with a big box of spacers of various widths sliding them into the available space as the car comes by on the line rather than having a computer calculate the dimensions and then have the proper size spacer CNC machined specifically for each car.

Just put in one bolt as a "holder" on each side while figuring it out. By the way, I used a long Philips's screw driver to align the holes in the trunion and the body. Holds things in place while you get that first bolt started and that way you have two legs of the triangle locked in.

Hopes this makes sense.....
 

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Discussion Starter · #6 ·
Lokki - Makes sense
Your technique requires a fully reinstalled rear suspension...
which I don't have yet... but am working on!
 

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A good leason in how to take things apart ... ;)

I willing to bet a beer that if you asked 20 owners to look under there 105 series coupes that the thicker shim will be on the same side.

So I had a look again at the chassis schematic that panel beaters were provided. This can be found here: http://www.alfabb.com/bb/forums/picture-room/856-my-1750-gtv-3.html, on page 3. And the dimension for where the trunion bolts is 780mm +1mm -0, or imperial 30.71 inches +0.04 -0. Thus pretty **** accurate, and surely no centering required ... ?

Is the thicker shim less than or equal to 1mm thicker than the other one?
Pete
 

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there were 3 type of shims : 1mm, 2mm and 3mm. Plastic washers (one for each side ) were the same. However, to get exactly for what we are talking , do you mean the "opened" shims which must drop in and then welded on the trunnion or the "triangle" spacers located at the very far of each trunnion's side ? For the the first ones still remains that they were 3 types. If you mean for the triangle spacers there were actually 7 types from 1.5mm till 3mm , by .5 mm step.
 

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Discussion Starter · #9 ·
there were 3 type of shims : 1mm, 2mm and 3mm. Plastic washers (one for each side ) were the same. However, to get exactly for what we are talking , do you mean the "opened" shims which must drop in and then welded on the trunnion or the "triangle" spacers located at the very far of each trunnion's side ? For the the first ones still remains that they were 3 types. If you mean for the triangle spacers there were actually 7 types from 1.5mm till 3mm , by .5 mm step.
I'm talking about the Wankel shaped triangle spacers - and I measured them and they do seem to be in .5mm increments.
 

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I'm talking about the Wankel shaped triangle spacers - and I measured them and they do seem to be in .5mm increments.

wankel spacers? oh that was really a fantastic description! So, yes the increments are .5mm , as mentioned before there were 7 types of them. Seems, the 2.5mm-3.mm were the common originally from the factory
 

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Okay the "wankel" spacers having increments of 0.5mm makes sense.

So r-mm how many of these "wankel" spacers do you have?
Pete
 

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Discussion Starter · #12 ·
Okay the "wankel" spacers having increments of 0.5mm makes sense.

So r-mm how many of these "wankel" spacers do you have?
Pete
Two... one on each side.
 

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r-mm,

Thanks for starting this thread; I never realized that the trunion spacers were different thicknesses. A couple of months ago, I dropped the axle and rear suspension on my Spider. Normally I always keep bolts, nuts washers, spacers, etc., together when I disassemble parts, but this time they all got tossed into the same can when I stripped the trunion for painting. After reading this thread, I went into the garage to check my trunion spacers, and yep, they're different thicknesses. Fortunately I haven't stripped and painted the spacers yet, so maybe I'll be lucky and be able to match them up to patterns on the body and determine which goes on which side, otherwise I'm in the same boat as you. If I hadn't read this thread, I'd have re-installed the reaction trunion with only a 50/50 chance of getting it right.

Best regards
 

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Discussion Starter · #14 ·
Hey Monsai, I'm not shy about asking questions...

I'm going to do some forensic photography in attempt to match the shims. I too haven't painted mine (which is a miracle b/c I'm on a tare with the POR-15) so hopefully I can get it right without test assembling.

r-mm,

Thanks for starting this thread; I never realized that the trunion spacers were different thicknesses. A couple of months ago, I dropped the axle and rear suspension on my Spider. Normally I always keep bolts, nuts washers, spacers, etc., together when I disassemble parts, but this time they all got tossed into the same can when I stripped the trunion for painting. After reading this thread, I went into the garage to check my trunion spacers, and yep, they're different thicknesses. Fortunately I haven't stripped and painted the spacers yet, so maybe I'll be lucky and be able to match them up to patterns on the body and determine which goes on which side, otherwise I'm in the same boat as you. If I hadn't read this thread, I'd have re-installed the reaction trunion with only a 50/50 chance of getting it right.

Best regards
 

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Has anyone experienced the consequences of switching them? You are all assuming that it is serious but I wonder if it really is? Would you even notice it?
 

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Two... one on each side.
So am I correct in assuming that if you put the wrong ones on the wrong side you could move the axle by a massive 2mm (ie. 2 x 0.5mm on both sides) ... and is this really worth loosing sleep over?

I would as Lokki suggested install the trunion and not fully tighten the attachment to the chassis bolts, then install your rear axle and lift it up and see how it fits in the middle. You can then move shims around if need be to make it better.

THEN once the car is on the road again get a 4 wheel wheel-alignment and they will be able to tell you if your rear axle is pushing directly up the centre of your car. If not easy adjustment by moving these shims around.
Pete
 

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Discussion Starter · #17 · (Edited)
Good call. Measured my shims and they're 4.5mm / 3mm. So i guess the total damage could be 1.5mm? It does sound small now that you mention it.

So am I correct in assuming that if you put the wrong ones on the wrong side you could move the axle by a massive 2mm (ie. 2 x 0.5mm on both sides) ... and is this really worth loosing sleep over?
 

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Can I ask a stupid question? What is the point of the 'wankel' spacer? Is it merely to make sure the trunnion is centered as best as possible as well as ensuring the chassis rails are not deformed when the 3 bolts either side are tightened up?

Mine, on replacing, were very tight and took quite a bit of knocking in - which in turn slightly deforms the main rubber bush, which in turn squeezes the replacement polybush shim. (and as it was cut to fit it in place it is now starting to push out!)

Matt
 

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Can I ask a stupid question? What is the point of the 'wankel' spacer? Is it merely to make sure the trunnion is centered as best as possible as well as ensuring the chassis rails are not deformed when the 3 bolts either side are tightened up?

Mine, on replacing, were very tight and took quite a bit of knocking in - which in turn slightly deforms the main rubber bush, which in turn squeezes the replacement polybush shim. (and as it was cut to fit it in place it is now starting to push out!)

Matt
I guess it was for both, centered and make it stronger in there. If it wasnt for centered the trunnion, then why alfa supplied these different? Then also comes the issue for a future or a past accident when repairing wasnt or couldnt be perfect as well.
 

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I recently read on a tech bulletin from alfa about how to take of and have new bushes on the trunnion sides. Well, now I can get why some very wise people here telling if these bushes looking good , leave the things as they are...
 
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