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After having new trailing arms installed in my 1966 coupe I was driving over a local bridge with a few potholes here and there and heard the sound of metal hitting the ground after hitting a pothole. The car made a strange crunching sound out of the back trailing arm section when starting from a stopped position along with some fishtailing when driving on the highway after that. Ends up some of the shims fell out??? Is this possible after hitting a pothole or were they installed wrong to begin with?
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Re: Shims fell out?
Gary, It would appear that a combination of two factors led to the shims falling out. One, if the mechanic used shims slotted on one end (originals were "closed" on both ends) and two, the trailing arm pivot bolt where the shims go was not tightened properly or sufficiently to hold the shims in. This is not to say that slotted shims are NG, I have them on my '67 and they've been there for years, just make sure the pivot bolt is tight.
Don -
Re: Shims fell out?
Don, I see the shims listed in many corvette supplier books and most show just open ended shims? Why are the "closed" versions not available? If they were stock.Comment
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Re: Shims fell out?
I have used the slotted shims and they work as advertised, when the pivot bolt is properly tightened. I assume that you used a visual inspection to confirm missing shims?
GaryComment
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Re: Shims fell out?
The inboard and outboard gap must be packed tight with shims with the car AT NORMAL RIDE HEIGHT.
Using shims on either the inboard or outboard side, push the trailing arm against the shim stack and and add or subtract shims as required until the correct toe setting is achieved. Then pack the empty side TIGHT with shims as required. The last shim installed should be the thickest used and tapped in with a small hammer. Thin shims will bend if you try to tap them in.
Then the bushing bolt should be tightened to specified torque - again with the car AT NORMAL RIDE HEIGHT, followed by a final toe check.
If the procedure is conducted as above, the chance of losing shims is slight. I believe that most "lost shim" cases are due to improper installation procedure.
DukeComment
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Re: Shims fell out?
Kinda knew that was the area causing the condition based on noise and movement of car, sent it in to the mechanic for inspection and correction.Comment
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Re: Shims fell out?
Gary,
When you replaced the control arms, were the replacements new GM or rebuilt from another source? If new GM, was the front bushing assembled/installed when they arrived or did someone else install it? If this bushing isn't assembled and installed properly, you will have the exact problem that you describe. The bushings must be assembled and pressed together in the control arm using a special tool, before the flair is formed on the end of the inner tube which locks the assy together.
The slotted shims work well and if assembled/secured properly, will not fall out.
MichaelComment
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Re: Shims fell out?
Gary, the reason for slotted shims v. closed end shims is that it is MUCH easier to install a slotted shim with the trailing arm fully installed. With the closed (1 hole on each end) shims, you have to line up each shim and place the pivot bolt thru the holes. Easier said than done especially with the car at ride height and a fully assembled rear suspension, not to mention an occasional rusty part.I believe that the correct closed shims are still available thru aftermarket suppliers. I know I've seen them. Try Long Island Corvette Supply in NY or Dr. Rebuild in Conn.
DonComment
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Re: Shims fell out?
I am told they were new GM arms repacked by an area shopComment
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Re: Shims fell out?
I think I saw the closed end shims at the Bairs display at Carlsile. I seem to remember they are more expensive than the open. Forty dollars for a kit comes to mind.Comment
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Re: Shims fell out?
My friend lost the shims on his 65 coupe while it was in an enclosed trailer. He tied the car down by the half shafts in the rear. At the end of our ride to Carlisle (400 miles) a couple of shims were on the floor under the left door.Comment
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Re: Shims fell out?
Some alignment shops are under the mistaken impression that tightening the pivot bolt will "crush" the walls of the frame against the slotted shims and bushing sleeve and hold them in place; it won't. As Duke mentioned, the shim pack must be TIGHT, with the last shim DRIVEN into place, then tighten the bolt. The reinforced side walls of the frame don't "crush" very far.Comment
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Re: Shims fell out?
When shimming the trailing arms on my 65 I used enclosed shims on the outside and slotted on the interior, this made the alignment much easier. I then used a plastic tie strap through the holes to insure that they would not fall out. I checked them every time I would put the car on a lift. If I was to have the car judged I would just cut the tie strap.
RayComment
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