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I have read through several threads but, have not found an answer.
I am working on fininshing a resotration project on a '68, This is one of those somebody else started, passed away and left to someone who is totally car clueless and just know that they have a Vette and want it all put back together so, they brought it to the shop. This is going to be a full on restification but, we are not redoing the chassis except what needs to be fixed. It has all new bushings, shocks, tie rods and ends up front. New steering ram etc etc.
It is a 427 - 4 Speed. Body is off and off to the fiberglass repair shop.
The chassis is assembled with engine and trans. I notices a few things not looking quite right so, I went through all the nuts and bolts to see what was tight/loose wrong or, right.
I get to the rear trailing arm pivot bolts and see the castelated nut several threads below the hole for the cotter pin. Looks like whoever put this thing together left out the trailing arm shims completely and that is where I am at.. So, what is a good baseline as far as number/thickness of shims to use for initial assembly? It is going to be a while before it is to the point of running/driving and getting an alignment but, I need an idea of where to start. Should I just put an equal amount of shims inboard and outboard on both sides?
The bushings are new BTW. I plan on using the later style stainless, slotted shims to make life easier for everybody.
Rookie suggestion: For now...place an equal amount of shims on each side of each trailing arm just to keep things snug. Then install cotter pins to keep nuts from falling off.
Also make sure stainless shims are secure so they do not “work their way out “ of the pockets.
I have read through several threads but, have not found an answer.
I am working on fininshing a resotration project on a '68, This is one of those somebody else started, passed away and left to someone who is totally car clueless and just know that they have a Vette and want it all put back together so, they brought it to the shop. This is going to be a full on restification but, we are not redoing the chassis except what needs to be fixed. It has all new bushings, shocks, tie rods and ends up front. New steering ram etc etc.
It is a 427 - 4 Speed. Body is off and off to the fiberglass repair shop.
The chassis is assembled with engine and trans. I notices a few things not looking quite right so, I went through all the nuts and bolts to see what was tight/loose wrong or, right.
I get to the rear trailing arm pivot bolts and see the castelated nut several threads below the hole for the cotter pin. Looks like whoever put this thing together left out the trailing arm shims completely and that is where I am at.. So, what is a good baseline as far as number/thickness of shims to use for initial assembly? It is going to be a while before it is to the point of running/driving and getting an alignment but, I need an idea of where to start. Should I just put an equal amount of shims inboard and outboard on both sides?
The bushings are new BTW. I plan on using the later style stainless, slotted shims to make life easier for everybody.
yes just put in an equal amount now. Slotted shims with the long stainless cotter pin (if your frame has the holes for it, you could drill them like i did)
This is a not a problem , but a step taken during restoration. Good luck!
Those trailing arm bushings do not look they were correctly installed. There should be an inner shell that the rubber bushing fits into. Are they poly bushings? If so, get rid of them and install the correct rubber bushings. The bolt and castle nut should come close as to allow a carter pin to be installed. Correct it while the body is off the frame. As mentioned above, start with installing the same amount of shims on either side of the bushing until you get to an alignment shop. Lastly, consider using stainless steel shims. Jerry
There are several things to check if these were installed correctly.
The inner metal bushing sleeves should be touching at the center of the trailing arm. Like this photo
The metal sleeve should have no gap on the outside against the trailing arm. If this is not the case the installation was incorrect. The trailing arm has to be supported on the inside while the bushings are being installed. So that the arms side walls are not bent inward. Also the bushing openings must be clean and smooth with no rust to make the install correct.
The next issue is the mount bolt it appears ether it is the incorrect length bolt or the frame has been bent at the mount It should appear as in these photos.
The original bolt part number is 458984 you can find originals on ebay like this.
Well funny you should ask about aligning it. I plan on doing my front & rear alignment while the body is off. Especially the rear since it so much easier to get at.
I have not done it yet or written it up, but I will.
This should give you a good idea:
I will be removing the springs for this job and duplicating the factory ride height of the spindles and trailing arms so the alignment is correct.
In the rear I may use a metal turnbuckle system to replace the shocks.
May try something similar in the front with all-thread and washers.
GM publishes the factory d and z-heights in the AIM.
I do my own alignments using mostly the dual 4 foot 1" aluminum I-beam method. And two tape measures across the car, and an angle tool for camber. A smartphone app works well for this these days..
The rear shims are such a pain, and an alignment shop would charge so much, (if you could even find one to do it correctly), I'll just do it myself.
Thanks for the replies. Here is another pic of the bushings. Looks like touching the middle and no gaps.
Not sure what is up with the bolt. It looks like the correct one but, even after I installed a washer under the head, it is too long to properly align the castelation om the nut with the hole-hole further out than the nut. I fint it hard to belive that bolt could crush the frame and I do not know what the measurement should be. If anyone has a number, it would be helpful.
I also noticed the spring bushinb bolts seem way too long. They use lock nuts so, I can cut off the excess,
Just did this job on my 68, the second trailing arm job for me.
Good advice and agree with all above. My 2 cents:
1. drill the holes for the long cotter pins and slotted trailing shims like 70+ setup. I can promise you drilling the holes with the body off is mucho better that drilling the holes with the body on. That way an alignment person can align the rear toe without having to take the trailing arms out (or bending parts, ugh)
2. I would be careful doing too much body work with the body off the frame. Better to do body work with the body on the frame, me thinks.
3. I am certain all frames are different, but lacking any more info, I would start with 0.250 (.0245 thick shim) on the inside and pack the outside with shims to fill the void. I think this will get you close. The pivot bolt tightens to 50 ft lbs at ride height, so I lowered to ground, installed wooden spacers to set and hold the ride height, then jacked up again and removed wheels to torque to 50 ft lbs. On my 72 I tightened the pivot bolt without packing the outside and decided you can bend the frame pocket before you get to 50 ft lbs.
4. The inner bushing sleeve needs to be filed flush with the big outer bushing washer to get good contact with the ta shims.
5. I suggest checking the bearing clearance while you are at this point too.
Leigh, please keep us posted on how your alignment goes and how you do it, I would very much like to know how to do as well.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Originally Posted by chuckwp
Yes, I know that. I am just trying to determine how to put it together for inital assembly.
I was pointing that out to leigh1322.
If you do have poly bushings in the t/a then leave them there. I have poly in mine and they haven't been an issue as long as they have lots of lube on them.
Just did this job on my 68, the second trailing arm job for me.
Good advice and agree with all above. My 2 cents:
1. drill the holes for the long cotter pins and slotted trailing shims like 70+ setup. I can promise you drilling the holes with the body off is mucho better that drilling the holes with the body on. That way an alignment person can align the rear toe without having to take the trailing arms out (or bending parts, ugh)
2. I would be careful doing too much body work with the body off the frame. Better to do body work with the body on the frame, me thinks.
3. I am certain all frames are different, but lacking any more info, I would start with 0.250 (.0245 thick shim) on the inside and pack the outside with shims to fill the void. I think this will get you close. The pivot bolt tightens to 50 ft lbs at ride height, so I lowered to ground, installed wooden spacers to set and hold the ride height, then jacked up again and removed wheels to torque to 50 ft lbs. On my 72 I tightened the pivot bolt without packing the outside and decided you can bend the frame pocket before you get to 50 ft lbs.
4. The inner bushing sleeve needs to be filed flush with the big outer bushing washer to get good contact with the ta shims.
5. I suggest checking the bearing clearance while you are at this point too.
Leigh, please keep us posted on how your alignment goes and how you do it, I would very much like to know how to do as well.
Hope this might help.
Thanks.
I have every intention of upgrading to the later style shims. Whoever did the first design should be raised from the dead and severly beaten.Having to do that much dissasssembly to align the real end is nuts!
Our shop is not doing the body work. It has been sent out.. However, our fabricators have braced the body and it is welded to a cart for transport.
I do not see an issue with the bushing sleeves interfering with the shims. I don't want to take the whole thing apart if I don't have to.
There are no plans to check the bearing clearance or, go into the engine at this point. It had been overhauled. I intend to use a pre-oil tool to be sure it has pressure before we start it.
How we are going to do the alignment is send it to a place that has an alignment rack/machine.
I have never messed Corvette IRS such is the reason for my quesstions.
All the replys have been very helpful. Thanks to all!
I was pointing that out to leigh1322.
If you do have poly bushings in the t/a then leave them there. I have poly in mine and they haven't been an issue as long as they have lots of lube on them.
You can't do a wheel alignment without the full weight of the vehicle on the wheels. You will need to load the chassis if the body is off, somehow.
Actually, not true. You can’t do an alignment without the suspension at ride height. You can accomplish this by removing the springs and shocks and bracing the suspension at ride height regardless of the body or engine for that matter being installed.
Again just my 2 cents but since rebuilding the trailing arm bearings are only slightly more fun than the OEM trailing arm shims/alignment (LOL's), and you want to keep your friend rolling down the highway, I would check the rear wheel bearing clearance with a dial indicator. When you rebuild them, the OEM setting is .001 to .008. If they are on the high end and still feel reasonably smooth, probably ok IMO. Lots of how to's on the internet for trailing arm bearings.
And agree, the designers who were around back in 63 when this design came out are likely not around today to do maintenance, ha, ha! If they were they would tell us to go buy a C8!.
My guess is you will eventually take it to an alignment shop and get it on a good machine? In that case you really don't need shims as they will probably have to change them to get it aligned. Now if you have to drive a significant distance do a through shade tree alignment before taking it in and have it machine aligned.
Make sure you get this style shim in stainless steel:
Oh I am positive you can do an alignment with a frame only. You will have to remove the springs though,
And the a-arms and trailing arms have to be at ride height. That's the tough part.
When the complete car is all back together I will check it again.
But I really do not think there is enough bending in a loaded vs unloaded frame to affect the alignment much.
I will measure it and see.
I would guess it would need a little touch-up after final assembly, in case the ride height is not spot-on.
I am curious to see how close I can get it.
Last edited by leigh1322; Mar 19, 2021 at 07:54 PM.
Oh I am positive you can do an alignment with a frame only.
There's a 30-year old restoration book (can't recall the title) on a '65 396 car in which they did the full alignment before the body drop. To obtain an accurate alignment, they chain-winched the frame downward to mimic the full curb weight of the car.
Last edited by barkingrats; Mar 20, 2021 at 10:56 PM.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
How do you compensate for the compression of the rubber bushings which may not even be on the car doing a frame off alignment? Imo, I don't see any advantage in doing 2 wheel alignments when only one is needed i.e. fully loaded and prepared suspension. Also, is that factory ride height? What if you now have smaller or larger diameter tires? Aftermarket springs? I guess you can get a ball park alignment but I don't see how an accurate 4-wheel alignment can be had.
Rear Trailing Arm Shims
