Chuck Gongloff

Several catalogs list replacement shims for 63-69 as the 2 hole style shims, and 70 and up as the slotted shims. With the 2 hole shims, the pivot bolt actually goes through the hole, making them non removable once they're put on. Also, to add and subtract shims, you have to remove the pivot bolt. With the slotted shims, the shims slip over the pivot bolt and are held in place not only by pressure, but by that long 6 inch cotter pin that goes through the frame. My 69 has the holes for the cotter pin in the frame. Does that mean I use slotted shims? Are the catalogs wrong? The new NCRS Judging Manual does not address this issue. Could this be a running change in 69? What style shims do you have? Any thoughts? Chuck

BigBlockVette

My car, built in July of '69 had holes in the shims. It was a real bear to cut apart. It also had the hole for the cotter pin through the frame (not used with hole type shims). When I rebuilt my trailing arms last spring, I replaced with the stainless slotted style from MidAmerica. I do not plan on being judged anyways, just for my own peice of mind. Thats what matters in my book.

Dwayne

TNT

Chuck, your 69 should use the double hole type. They are a little longer than the slotted type. As early as VIN year 1970 ---16629 started using the slotted type of shim. Also both of my mid to early 70 vetts have the hole for the cotter pin but use the double hole shim. Thad :blueangel:

Paul L

Chuck,
Just to put this into perspective, these are the SS slotted shims. I do not have an answer to your question but a pic can put people's discussions into a focus. I do not have pics of the hole/slot versions. Thanks.

Smokehouse69

My July 14 build date roadster came with the hole type shims, but also had the holes for the cotter keys. When I rebuilt my arms this spring I replaced them with the stainless steel hole and slot. I don't plan on having my car judged, and if I ever do, I'll take the deduction for the shims.
Funny thing about it is that the Chevy Chassis Service Manual for 1969 shows the slotted type shims as does the AIM. The AIM shows the slotted type shims, along with a note that the cotter pins were "added" at some time, and the shim part number was changed at some time during production, but no date was shown for the change. The part number for the shims were 3846595-6-7-8 and were changed to 3965192-3-4-5. I would assume that the change if it took place in the 69 production year, took place in the extended production period, of August through December, when 70 models should have been produced.

63Banshee

Well, I’m going with slotted shims. This is one of those rare parts that will not be replaced as it was because of a bogus original design.

Pedro'74

Man, talk about bogus... I can't even imagine how painful it is to align a car with the non-slotted shims! :crazy:

-Pedro

Chuck Gongloff

Seems like the holes for the cotter pins arrived long before they used the slotted shims. I'm going with the slotted ones anyway. I've fooled with the 2 hole shims many times before. As others have said, it's a real PITA when you go to align the car. I might used a mix of several thick 2 holers, and several smaller slotted. Will think about it while my trailing arms are being rebuilt. Curious question...any 68 owners have holes drilled for the cotter pins? My 69 was built in late August of 69 and has the holes. Chuck

GaryS

Chuck, I would think that, using the advice of others who have cars of similar build dates, you should be able to go with the slotted. On the other hand, how much of a deduction is it? My alignment guy wouldn't even consider doing an alignment on my 66 if I had installed the shims with the holes in them.
Gary

Rowdy Rat

Chuck,

My 1969 convertible and early 1970 coupe both had the two hole style shims. As mentioned by several people, they are a pain to work with and if the car is not being shown, the slotted shims with the cotter pin are a much better choice.

You are correct regarding the hole for the cotter pin required for the slotted shims... It was there LONG before the shim switch was ever made. What's even more confusing is that the 1969 AIM even references the use of the slotted shims/cotter pin. I'm with Thad though, in actual practice, I have never seen the second style shims and cotter pins on anything earlier than a late 1970.

By the way, congratulations to both you and Pat on the great times you turned with the '69 at Cecil County (you let her beat you again though! :) )!

Regards,

Robd

I copy threads that have useful information that I may need when I re-assemble my car. The following thread was on the ncrs board a while back. It may give you additional information. I have removed all names in the re-post.
hope it helps

Trailing arm shims - 66 corvette
Date: Tuesday, 5 June 2001, at 7:32 p.m.
I'm debating on whether to use slotted or unslotted shims. The original assembly was unslotted but this will make final alignment in a shop difficult. I don't know what the points deduct is for slotted shims?

Re: Trailing arm shims - 66 corvette
Date: Wednesday, 6 June 2001, at 5:35 a.m.
In Response To: Trailing arm shims - 66 corvette
At the risk of saying something dumb again, switching to slotted shims will also require drilling a hole in your frame to accomodate a large cotter pin.
The presence of the cotter pin will be noticed and probably a small deduct made during judging.
If you are concerned with originality, and being that a rear wheel alignment is an infrequently required task on our semi-retired gently driven things of beauty, why not just leave it original and pay a little extra for the alignment.
I think Joe made the suggestion once about using slotted shims for calculation purposes and then put unslotted in for final butt'y. That made a lot of sense to me.

Re: Trailing arm shims - 66 corvette
Date: Wednesday, 6 June 2001, at 7:44 a.m.
In Response To: Trailing arm shims - 66 corvette
When I assembled the trailing arms on my '66, I went through the same thought process as you. After talking to an alignment specialist familiar with Midyears, I decided to go with the the slotted shims out of convenience. If you try to align the car yourself, you will see how time-consuming it is to remove the support bolt everytime you want to change a shim. There's a lot of discussion in the archives about this topic (search "shims" or "trailing arms" or "rear toe". The JG assigns 6 points to the trailing arm assemblies and spindle supports. A judge will have to tell you what you would get dinged for slotted shims.

Re: Trailing arm shims - 66 corvette
Date: Wednesday, 6 June 2001, at 12:09 p.m.
In Response To: Trailing arm shims - 66 corvette
I wouldn't even CONSIDER using the non-slotted shims REGARDLESS of point deductions. Actually, I think that it's very difficult to tell what type shims are installed, but even if it's discernable and judged I would NEVER, EVER, EVER recommend using the non-slotted shims. These make the rear toe adjustment extremely laborious and most alignment shops will charge by the hour for 63-82 Corvette rear alignment. What's worse is the fact that you are unlikely to get a good alignment. The technician will undoubtedly be inclined to "button things up" when he's got the alignment "good enough" (or maybe not even "good enough").
You do not have to use the retaining cotter pins with the slotted shims. My original owner 69 was originally supplied with a combination of slotted and non-slotted shims. These got changed to ALL SLOTTED at my request at the first alignment at the Chevy Dealer. I've never used cotter pins and I've never, in almost 32 years, had any problems with losing shims.

Re: Trailing arm shims - 66 corvette
Date: Wednesday, 6 June 2001, at 5:10 p.m.
In Response To: Re: Trailing arm shims - 66 corvette
when I replaced the torque arms in my '67 there were non slotted shims installed from the factory. I replaced them with the stainless slotted type and didn't need a hole in the frame for the cotter pin, since I didn't put them in.
If you install the shims and push them down into the frame, and then torque down the front bolts, with the rear wheels at riding height, not sagging on a jackstand, they won't come out.

Date: Thursday, 7 June 2001, at 9:15 a.m.
In Response To: Re: Trailing arm shims - 66 corvette
I could have sworn that there was a fairly recent discussion (either here or on the CRPL) where somebody posted that they had used slotted shims on a car without a cotter pin, and the shims had now rotated out of the frame slot and were ready to fall off completely.
General advice was either to put a cotter pin, or use non-slotted shims.




[Modified by Robd, 8:57 AM 10/26/2001]

Chuck Gongloff

Thanks for the great info, guys. I'm fairly sure I'm going slotted. Once they're installed it's tough if not impossible to tell by looking at the shims themselves. The cotter pin is/would be a dead give-away. I just want to make it easy, as fooling with the "2 holers" is no fun. I've "been there, done that" many times before. Stan....I didn't "let" her beat me...she regularly beats me EVERY time we go to the drags. She turned a 13.75 to my best of 13.82. We used to own two C4 coupes...one L98 and one LT1...not at the same time. When we ran those cars, she always beat me by 1--2 tenths. Chuck

Paul L

Just a second-hand opinion. From a person who advises me on Corvette repairs. He was the local Chev dealer Vette specialist for many years. Use the cotter pin or the slotted shims will come out. And I will in the spring when I get enough nerve to try to get the bolts out.

Chuck Harmon

Using double hole shims WAS and IS a very bad idea. The slotted version is a great improvement as long as you use the cotter pin. Using the double hole version for originality's sake is like replicating the sloppy paint over-spray on the engine. I want my car to be as Bubba Free as possible. I'm not interested in copying original Bubba manufacturer design and assembly mistakes. The air and water in my tires and radiator isn't from St. Louis either!

Chuck

R1234

Chuck, my early build date 68 does not have a hole for the cotter pins. The original shims were the two hole.