My 40GT Rear Suspension (Lower Wishbone, Inner Bushing)
With the wishbone (lower rear control arm) installed in my 400gt, you can see the old inner bushing is squished to one side. There is nothing that absolutely keeps it centered -- it's a press fit than can shift over time. If pulled consistently, it will squish and the wishbone will end up uncentered. In my case, the inner wishbone pulled back over time because of a broken trailing arm modification, squishing the bushing to the rear, which contributed to excessive toe-in. It was this toe-in which initially raised the red flag, causing me to inspect the suspension in detail.
The trailing arm (technically: leading link, but I doubt anybody calls it that when you go to order parts) had a screw adjuster added 20 years ago that finally failed (welds cracked and adjuster bent). This effectively lengthened the arm as it bent in. Apparently, the rear wheels are normally pulled in to more toe-in as the car is driven. This link holds them back "out" into the correct toe-in position. (At least that is the condition with my "damaged" suspension.)
In the above photo I have added a brace/adjuster so that I can adjust the length of the arm to return it to the correct length. Once that is determined I will weld the old piece back in to have a solid arm. The red lines here represent my measurement points.
The upper bushings seem to be ok for now, the wishbone is centered on the bushings.
It appears the factory did not intend for rear toe to be adjustable. I've heard this from several sources, including Burtoni.. If there is any adjustment to be had, a small amount could be had here at the trailing arm "washers." The delrin rings, though of different width, don't have the strength to hold the arm in position. In addition, the bushing itself would have to be pressed in one direction or another. The fact that the Miura and Islero S have different arrangements suggests to me that the 400gt arrangement was an early attempt which was improved upon down the road. ie: Having no obvious and clear adjustment is a pain in the butt!
Once out of the car the bushing problem is even more obvious. On the left you can see the bushing is shoved over to one side. On the right you can see that it was also squished in towards the frame. The shiny surfaces are caused by the wishbone rubbing against its bracket. Oy!
Another photo on the left of the old bushing offset, and on the right the bushing has been pressed out. Here you can see the retaining collar which is still pressed into the arm. It needs to be pressed out as well to make way for the new bushing assembly.
Left photo is the side the collar is pressed in from, right is the opposite end of the same collar..
The replacement bushing assembly (thanks Jack!)
The new installed bushing. $30.95 each from Ultimate in Florida, Genuine Lamborghini Part # 8921702. Cost $20 to have both old bushings pressed out and both new bushings pressed back in. Not bad! Common's Auto in South San Francisco, ask for Glen. Don't tell him it's a lambo. :)
Make sure the collar is pressed into the control arm ("wishbone") all the way, which is about 1/16" down from being flush with the arm, as you can see by the picture on the left. The picture on the right shows where the arm was rubbing against the bracket (silver area) -- no more of that!
The control arm pivot hole is tapered (smooth) to accept the rubber bushing and its metal collar in a compressed fit. The lip on the metal collar is pushed down until it seats on a shoulder, as shown above. The collar "lands" are compressed into the tapered hole. There is no adjustment to be had here, the alignment is determined by the location of the metal collar on the rubber bushing (see Jack's photos above) which is done at the factory when they make the bushing.