66 Rear alignment shims

[Ed K.]

Re: 66 Rear alignment shims

Whoops - some of that 1/2" play at axle center is dimensional clearance buildup at the bolt going thru the bushing thru the chassis. A few thousandths is needed for each and the axle center is 17" away from the pivot at the bolt.

[Wayne W.]

Re: 66 Rear alignment shims

Don't get hung up on the number of shims or the size. Just use enough of different sizes so the alignment guy can move them around as needed. Fill the opening, no more, no less.

[Joe L.]

Re: 66 Rear alignment shims

The sleeves that must come in contact with each other when properly loaded are the inner sleeves. The gap in the outer sleeves, visible in the pic's above, does change from one setup to the next, depending on the dimension (thickness) of the control arm.

If the inner sleeves are not butted together when installed, the assembly will not be stacked and the pivot bolt in the control arm will not secure the arm properly.

Michael-----


There is no way to positively discern if the inner sleeves are butted together by simply looking at the end of the trailing arms. However, if the outer sleeves are butted together (or VERY close to being butted together), one can infer that the inner sleeves are, too. Obviously, once the outer sleeves are butted together, no further compression of the bushings is possible even if the inner sleeve are not butted together at that point. Before the retainers are installed one could, of course, try to "peer into" or otherwise "probe" the center sleeves to see if they are butted but it would be difficult and I don't know of anyone that does that.

Assuming that a very slight gap existed between the inner sleeves when the outer sleeves were fully installed, I am very confident that gap would be eliminated when the retainer was properly compressed and flared.

[Joe L.]

Re: 66 Rear alignment shims

Thanks, but previously after I put shims in there seems to be a considerable amount of play. About 1/2" in/out at the axle center. I was able to begin hammering an 1/8" shim in but could not get the last inch in. I guess I just fill it with several thin ones? Should I be hammering? It's impossible to hammer the thin shims without bending them. AND most importantly... I greatly appreciate all the help.

Ed------


It is DEFINITELY impossible to hammer in the thin shims. The way to do this is to determine what the last THIN shim required is, then remove one of the thickest shims, insert the thin shim, and tap in the thick shim. If it's required, at all, tapping in one of the shims should only be required of ONE shim on ONE side of the arm. It should not be necessary to "beat" the shim in; just tap it in.

Also, I absolutely do not recommend the use of "2 hole" type shims. Use the SLOTTED shims. Otherwise, the rear end alignment will be a nightmare for the shop. Often, this will translate into a high cost for you since most shops only do 63-82 Corvette rear alignments on a "per hour" basis. The longer it takes them, the more you pay. Using the 2 hole shims virtually guarantees it will take them a long time.

It is virtually impossible for anyone to discern that the slotted shims have been used after they are installed. If they are tucked down into the frame pocket as they should be, they will not fall out even if no cotter pins are used for retention.

Even if the slotted shims resulted in a point deduction, I would still recommend using them.

[Joe L.]

Re: 66 Rear alignment shims

Heart valve challenged leads to new use for wheel shims..and milk crate..paint stirrer, but supports the arm assembly without strain for me. Please see attached photos. I think all looks OK except for rust that's beginning to form. Have to sand it out. But, now what?

Ed-----

I agree with the others. These look just fine to me. However, I also agree with your assessment regarding the corrosion. While I can't see very much of the arm, the little that I can see worries me a bit. Corrosion on these arms can be a problem and a lot of it is often hidden. If it's serious, the best plan is usually to scrap the arm and get a new one. However, I would assume that the shop that rebuilt the arms inspected them prior to rebuilding. At least, I hope they did.

[Michael H.]

Re: 66 Rear alignment shims

Michael-----


, if the outer sleeves are butted together (or VERY close to being butted together), one can infer that the inner sleeves are, too.

I don't think anyone is getting this. Simply pressing the pair of bushings into the control arm until the outer/visible sleeves come in contact with each other (or neally so) is only the first step.
At that point, the inner sleeves are, by design, still at least 1/8" or more apart.

The second step compresses the bushings which moves the inner sleeves toward each other until they actually make contact.

The inner edge of the inner and outer sleeves are NOT at the same dimension to begin with. It's the second press operation that compresses the bushing and forces the inner sleeves to make contact.

It's not possible to LOOK at an assembled bushing/control arm assembly and determine if the inner sleeves are in contact with each other. The only way you know when this occurs is when the force/torque required to compress the assembly suddenly increases.

The drawing that I posted above shows the completed bushing/control arm after the assembly is pressed together until the inner tubes are in contact with each other.

The bushings are to be compressed together until the inner sleeves contact each other BEFORE the inner tube is installed and flaired.

[Ed K.]

Re: 66 Rear alignment shims

My concern arose when not being able to insert the old shims. Since neither chassis, arm or shim changed I would think the bushing assembly thickess becomes the only dimension that could change and might be a way to tell if the bushing is assembled correctly. Mine measures 2.253" (a paper thickness over 2 1/4). I'm not able to insert the last old 1/8th shim. Or, am I missing the point?

[Michael H.]

Re: 66 Rear alignment shims

My concern arose when not being able to insert the old shims. Since neither chassis, arm or shim changed I would think the bushing assembly thickess becomes the only dimension that could change and might be a way to tell if the bushing is assembled correctly. Mine measures 2.253" (a paper thickness over 2 1/4). I'm not able to insert the last old 1/8th shim. Or, am I missing the point?

If the inner sleeve is not properly set with the bushing compressed completely, the overall dimension of the bushing pack will increase.
The drawing below shows the bushings installed in the control arm but before being compressed. The outer sleeves are in contact but the inner sleeves have a gap. When the inner sleeves are compressed and the inner ends contact each other, the tube can then be installed and flaired.
Actual contact of the inner sleeves is critical. If there's a gap after the tube is installed and flaired, the shims will not be secured properly. The frame wall, washer, tube, and inner sleeve must be a solid stack without a gap between the inner sleeves.
I'm sure most of the guys that rebuild these control arms are aware of this important procedure and assemble the bushings properly.

It is possible that the new bushing/washer stack that you installed is actually 1/8" wider than the original but I would want to be sure before I installed the control arms.

[Michael W.]

Re: 66 Rear alignment shims

Well, I sure learned something new. Thanks Cranky!

[Ed K.]

Re: 66 Rear alignment shims

Thanks for your drawing rework. Very very helpful. I think I got it. See my following red font comments. If the inner sleeve is not properly set with the bushing compressed completely, the overall dimension of the bushing pack will increase. The drawing below shows the bushings installed in the control arm but before being compressed. The outer sleeves are in contact but the inner sleeves have a gap. When the inner sleeves are compressed and the inner ends contact each other, the tube can then be installed and flaired. The outer sleeves should show distortion when compressed 1/8th beyond contact. Agreed?
Actual contact of the inner sleeves is critical. If there's a gap after the tube is installed and flaired, the shims will not be secured properly. Because the sleeves can move inwards under forces exerted when driving. Am I correct? The frame wall, washer, tube, and inner sleeve must be a solid stack without a gap between the inner sleeves.
I'm sure most of the guys that rebuild these control arms are aware of this important procedure and assemble the bushings properly.
It is possible that the new bushing/washer stack that you installed is actually 1/8" wider than the original but I would want to be sure before I installed the control arms.

[Michael H.]

Re: 66 Rear alignment shims

The outer sleeves should show distortion when compressed 1/8th beyond contact. Agreed?

Because the sleeves can move inwards under forces exerted when driving. Am I correct?

The outer sleeve doesn't distort. The rubber in the bushing crushes as the assembly is compressed.

Correct on the sleeve moving inwards which unloads the stack. (and the shims) That allows the bushing sleeves to rotate as the control arm goes through it's travel. That's why shims fall out if the bushing isn't installed correctly.

I should have posted both pictures in the same post.

[Joe L.]

Re: 66 Rear alignment shims

I don't think anyone is getting this. Simply pressing the pair of bushings into the control arm until the outer/visible sleeves come in contact with each other (or neally so) is only the first step.
At that point, the inner sleeves are, by design, still at least 1/8" or more apart.

The second step compresses the bushings which moves the inner sleeves toward each other until they actually make contact.

The inner edge of the inner and outer sleeves are NOT at the same dimension to begin with. It's the second press operation that compresses the bushing and forces the inner sleeves to make contact.

It's not possible to LOOK at an assembled bushing/control arm assembly and determine if the inner sleeves are in contact with each other. The only way you know when this occurs is when the force/torque required to compress the assembly suddenly increases.

The drawing that I posted above shows the completed bushing/control arm after the assembly is pressed together until the inner tubes are in contact with each other.

The bushings are to be compressed together until the inner sleeves contact each other BEFORE the inner tube is installed and flaired.

Michael and Ed-----


The bushing installation is a 2 step process; not a 3 step process. The steps are as follows

1) The bushings are pressed into the trailing arm orifices until the flanges of both are seated against the trailing arm. This installation can be done using GM tool J-7055-1, another improvised tool, an arbor/hydraulic press, etc. When the bushings are fully installed, the flanges will be seated on the arms outer surfaces and the inner end of the outer sleeve (i.e. the sleeve with the flange) are in contact (or, nearly in contact). When this is completed, step one of the process is finished;

2) After the above is completed, the chamfered washers and retainer (flared end tube) are installed and the bushings compressed and retainer flared IN ONE OPERATION using tools J-8111-23 and tool J-8880-5.

The above procedure is how GM specifies the bushing installation in the service manuals and is how I and most other folks do it (WITH THE CAVEAT I DESCRIBE BELOW). It is not possible to complete the bushing installation in a THREE step procedure. In other words, it's not possible to install the bushings, compress the bushings in a second step and then install the retainers/chamfered washers in a third, separate step. It is the retainers that maintain the compression on the bushings.

Now for the caveat: using tools J-8111-23 and J-8880-5 or similar aftermarket tools can be difficult. However, it can be done (I've done it successfully). As an alternative to this procedure, though, the bushings can be compressed in a special tool/fixture and the retainer flared in a secondary operation WHILE THE ASSEMBLY REMAINS IN THE TOOL/FIXTURE. This procedure works quite well and makes everything easier. However, most folks don't have this tool/fixture and it was never available from GM/Kent-Moore.

Also, when the outer sleeve (i.e. the sleeve with the flange) of the bushings are in contact, the inner sleeves are 0.085" apart (I measured it with 2 GM bushings butted together). Compression of the bushings as described above takes up this gap and also further compresses the elastomer component of the bushings. As I recall, the compressed thickness of the bushings installed in the trailing arm, measured between the outer surface of the chamfered washers on each side, with GM bushings is 2.06". I'm not sure about that dimension at the moment, though. It's very slightly different for aftermarket bushings not marked "Clevite" (the GM source) since the elastomer durometer is usually different for these bushings.

[Ed K.]

Re: 66 Rear alignment shims

The outer sleeve doesn't distort. The rubber in the bushing crushes as the assembly is compressed.

Wow. Totally missed understanding that the inner and outer are not one piece. I feel dumb. Of course the rubber crushes when continuing to push. It's 2:42 AM here -Eastern time. Fell asleep on the couch earlier. I believe I'm arranging this post correctly. I don't have a scanner at home, so need to do a digital CAD drawing to illustrate, as attached.

So, I should measure the shops sleeve. There should be a 1/16th difference as shown in my drawing before any compression is done. Correct??? [ATTACH]20557 Please disregard "Drawing 1". Don't know how to delete it from attachment. It's correct, except rotated. Use "bushing-sleeve.pdf" drawing. Good night. Have to be in work in AM.

[Timothy B.]

Re: 66 Rear alignment shims

There was a fellow I met in Carlisle that made a tool to flare the bushing after compression. My memory tells me the total (inner and outer) stack of shims being approx 3/4" +- 1/16".

Joe, can you refresh my memory on the lug nut procedure to flare the sleeve you mentioned a long time ago used with a steering wheel puller??

[Wayne W.]

Re: 66 Rear alignment shims

Wow, We are beating this horse to death here. I'm telling you that any bushing compressed as much as this one, and they actually got the sleeve to flare correctly, will be compressed enough in the center to close the gap in the bushing. There is never any guarantee that the same original shims will fit the hole. I wouldn't worry about it period.