C3 strut rod bushing issue

[Thomas H.]

What might cause this to happen?







These are new strut rods and have less then 500 miles on them.

Tom

[Joe L.]

Re: C3 strut rod bushing issue

What might cause this to happen?







These are new strut rods and have less then 500 miles on them.

Tom

Tom-----


Did you install the rods with the caps on either side of the bushings?

[Thomas H.]

Re: C3 strut rod bushing issue

Tom-----


Did you install the rods with the caps on either side of the bushings?

Joe,

Not at the trailing arm end, only on the differential side. The photo shows the trailing arm side. The differential side is fine.

Both the left and right sides are doing it.

Tom

[Joe L.]

Re: C3 strut rod bushing issue

Joe,

Not at the trailing arm end, only on the differential side. The photo shows the trailing arm side. The differential side is fine.

Both the left and right sides are doing it.

Tom

Tom-----


Yes, you've done it correctly then---the caps are used only at the center bracket end of the rods and not at the bearing support fork end.

I've not seen this sort of problem before. However, I can think of 2 possibilities:

1) The bushings may be defective in some way, allowing the elastomer to "escape" from the outer bushing steel shell. You might try replacing these bushings with GM bushings (even though I believe that aftermarket and GM are derived from exactly the same manufacturing source). The GM part number is 3775762;

2) These strut rods are the "reproduction", fabricated type. The original strut rods were a one-piece, forged unit with vulcanized-in-place bushings. This type of strut rod uses bar stock for the rod section and welded-on ends. It MAY be that there is some slight problem with the fabrication that puts the ends in an excessive "bind" on installation.

One other thing: one will often see some displacement of the elastomer even on original strut rods. However, I would not expect to see anything like this much after only 500 miles of service.

[Thomas H.]

Re: C3 strut rod bushing issue

Joe,

I have the original rods that came out of the car. I also have a set of GM bushings (I don't recall the exact PN, but they are in the GM packaging). I suppose I should press the old ones out and put the GM one's in and try the old rods for a bit and see what happens.

What should the orientation of the strut rod bracket be when mounted on the differential? It has a flat side and a "stepped" side. If this was not mounted correctly, would it cause this to happen? Will it even work if it was mounted wrong? I had the car aligned last fall and we had no problems getting it aligned, it took a while, but no problems.

Thanks,
Tom

[Harmon C.]

Re: C3 strut rod bushing issue

Tom
The bracket will only bolt on one way because the holes are closer together on one side.

[Thomas H.]

Re: C3 strut rod bushing issue

Lyle,

I had the washers installed at the bracket end. The trailing arm end has no washers.

I looked last night at the drivers side strut rod, which is still installed in the car, at it also appears to have the rubber being pushed to one side on the trailing arm end only.

I remember (it was over a year ago and my memory isn't what it used to be......) setting the car down so the suspension was loaded before tightening the bolts, but maybe the serrated edges of the bushing were tight enough in the trailing arm so that when I lowered the car, the bushing bound up a bit and then when I tightened the bolts, it secured the bushing in that bound up position forcing it to work its' way around and out to a neutral position over time............?

I don't know. Either way, I'll be putting new bushings back in and paying attention to make sure they are in a neutral position before I tighten anything.

Tom

[Bill M.]

Re: C3 strut rod bushing issue

One possibility is that the original bushings are bonded (glued) to the inner and outer sleeves. This is done to increase the bushings durability. Looks like these weren't. (I'm not sure that the originals were bonded to both sleeves.)

[Joe L.]

Re: C3 strut rod bushing issue

One possibility is that the original bushings are bonded (glued) to the inner and outer sleeves. This is done to increase the bushings durability. Looks like these weren't. (I'm not sure that the originals were bonded to both sleeves.)

Bill-----


The bushings on the original strut rods or GM SERVICE strut rods were vulcanized-in-place. There was no outer steel shell to the bushings as is the case with SERVICE bushings.

[Bill M.]

Re: C3 strut rod bushing issue

Bill-----


The bushings on the original strut rods or GM SERVICE strut rods were vulcanized-in-place. There was no outer steel shell to the bushings as is the case with SERVICE bushings.

Hi Joe:

I've forgotten what my original bushings looked like. I installed GM service bushings in 1978. I don't have the bushing problem that Tom is having. Maybe the GM service bushings are bonded to the outer sleeve?

[Joe L.]

Re: C3 strut rod bushing issue

Hi Joe:

I've forgotten what my original bushings looked like. I installed GM service bushings in 1978. I don't have the bushing problem that Tom is having. Maybe the GM service bushings are bonded to the outer sleeve?

Bill-----


I THINK that the GM SERVICE bushings have the elastomer (rubber) vulcanized-in-place or otherwise bonded to the outer steel shell, just as the original bushings were vulcanized-in-place to the strut rod, itself. However, it's possible there has been some sort of change in the manufacturing process which results in the sort of problem seen here..

[Steve L.]

Re: C3 strut rod bushing issue

Joe,
Do you know if the replacement rods, with the included bushings, sold by Paragon(and others), have the bushings vulcanized in place as the original strut rods? Or do they just press fit the bushings into the struts with the outer steel shell and sell it as a unit.


There doesn't seem to be a lot of difference in price by buying 2 bushings and pressing them in yourself or buying a complete ready to use strut.

Steve L
73 coupe since new

Bill-----


The bushings on the original strut rods or GM SERVICE strut rods were vulcanized-in-place. There was no outer steel shell to the bushings as is the case with SERVICE bushings.

[Joe L.]

Re: C3 strut rod bushing issue

Joe,
Do you know if the replacement rods, with the included bushings, sold by Paragon(and others), have the bushings vulcanized in place as the original strut rods? Or do they just press fit the bushings into the struts with the outer steel shell and sell it as a unit.


There doesn't seem to be a lot of difference in price by buying 2 bushings and pressing them in yourself or buying a complete ready to use strut.

Steve L
73 coupe since new

Steve-----


The 75-79 style rods with "large" ends which are also SERVICE for 63-74 definitely have the bushings vulcanized-in-place. However, the 63-74 reproductions with "small" ends, I'm not sure about. The ones I've seen have the steel-shelled bushings installed. However, there may be others out there now. You'd need to ask the vendor to be sure.

[Sal C.]

Re: C3 strut rod bushing issue

Tom,

I recently purchased a '71 LT1 that had just undergone an extensive body off restoration. I purchased it with about 20 miles on it. When I put it up on a lift I noticed the exact problem you have showed us. Also both sides.
I believe the problem to be a sub-standard reproduction bushing installed during the resto. I replaced all 4 bushings with the GM service units and have not had this problem since, and I have been driving it.
There is alot of good reproduction parts out there, but there is probably a greater amount that is pure junk.

Sal

[Thomas H.]

Re: C3 strut rod bushing issue

Sal,

When I sent one back to the vendor I bought it from, they said that this should not have happened and they would replace both for free. A few days later I received two new strut rods. The new ones also have pressed in bushings so I'll keep an eye on them and see how they hold up.

I made sure that the car was on the ground before I tightened the bolts so the bushings are in a neutral position to start with. (I thought I did this on the previous ones too, but I can't say for sure)

We'll see...............

Regards,
Tom

PS: good luck with the LT1!