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Safety question: Is it safe to pull TA bolt with the car sitting on its suspension?
I'm about to change the toe in/out on my rear wheels. Because I don't have the slotted shims I will have to pull the trailing arm bolt (where the trailing arm sits in the frame pocket) to relocate a shim from the inside of the TA to the outside of the TA. As of this moment, the weight of the car IS sitting on its suspension and the car is on my 4 post lift where I intend to perform my car's alignment. I've never pulled the TA bolt before with the weight of the car sitting on its suspension and I have a healthy fear of / respect for the strength and danger of the rear leaf spring and I want to make absolutely sure it's safe for me to pull the trailing arm bolt. My plan is to leave the car sitting on its suspension while I pull the TA bolt and relocate a shim from the inside of the TA to the outside of the TA. With the weight of the car sitting on its suspension, is it safe to pull the TA bolt? In other words, is the TA going to violently / dangerously move when I pull the TA bolt?
Thanks in advance for helping me with this question. Obviously, before I begin my project I'll wait for some responses.
Current picture of my car today with the weight of the car sitting on its suspension and the car is on my 4 post lift.
most newer shims are slotted and just require the bolt to be loosened to remove them. Personally I would never remove the Trailing arm bolt with weight on the suspension or with the spring attached for that matter. That's just my opinion though, someone else may disagree.
Look at where the spring is pulling down on the back of the trailing arm, and the pivot point of the wheel spindle, and take a guess what the front of the trailing arm is trying to do if the bolt is pulled out. For a hint, remember your teeter totter experiences back in grade school when one of the kids on the board suddenly hopped off.
Hi, glad you asked. A big NO. We have a '68 and the suspensions are very similar. Only safe way to do it is to remove the spring and other needed suspension parts. There are youtube vids that will help you do that. Make sure you use the right support, etc. as you do.
Our '68 also didn't have the slotted shims - those came in '69. Even though our car is an L71 and I'm keeping almost everything stock, I drilled the frame and installed slotted shims and a long cotter pin like '69 and up. My alignment guy almost threw me a party. It's one of the craziest designs I've seen. But we love these vettes.
If you do, please set up a tripod and video the whole thing. It might just end up on a OSHA video. I have flashbacks to those Shaking hands with danger safety videos from the 80's............
I don’t think there is anyway to accurately predict which way the pivot end of the trailing arm will react if the bolt were to be pulled out under load, and some of those reactions could be hazardous at best, maybe even deadly. Not a chance I’m willing to take but it’s your choice. At a minimum what are the chances that you would be able to get it lined back enough to get the bolt back in? If not, you’d then be faced with unloading the spring with the pivot end unrestrained.
Never occurred to think about this but seems to be a good point in favor of slotted shims.
You could probably remove the bolt safely by strapping the half shaft of back end of trailing arm forward to the frame cross member but with the spring tension just banging the bolt out and getting the end of the trailing arm lined up in place to get the bolt back in would probably be a nightmare.
To answer my own question I went to the 63 shop manual. It states loosen the pivot bolt and add or remove slotted shims. So where did the non-slotted shims come into the picture?
To answer my own question I went to the 63 shop manual. It states loosen the pivot bolt and add or remove slotted shims. So where did the non-slotted shims come into the picture?
I have read everyone's responses above and appreciate everyone's input. Thank you. I don't want anyone to think/perceive that I'm arguing because after all, I asked the question because I am concerned about MY safety, but no where in the 1967 Corvette Chassis Service Manual is there anything mentioned about detaching the leaf spring when performing the toe-in alignment. Here is the entire toe-in alignment paragraph:
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"Wheel toe-in is adjusted by inserting shims of varying thickness inside the frame side member on both sides of the torque arm pivot bushing (figure 10). To adjust toe-in, remove torque arm pivot bolt; then position torque arm to obtain specified toe in. Shim the gap toward vehicle center line between torque arm bushing and frame side inner wall. Shim the outboard gap as necessary to obtain solid stack up between torque arm bushing and inner wall of frame side member. After correct shim stack has been selected, install pivot bolt and hardened washers making sure that all shims are retained. Torque nut to specification and install cotter pin. If specified torque does not permit cotter pin insertion, tighten nut to next flat."
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In 1967, the original trailing arm shims were not slotted. Slotted shims came into the picture in 68 or 69 I believe (I'm not a C3 expert). So, if EVERY rear wheel alignment performed on a 67 Corvette involved the original shims with holes (not slots) how did the dealerships perform the toe-in alignment if they didn't detach the leaf spring???
Last edited by CADbrian; 03-25-2024 at 05:48 PM.
Reason: added spacing
Never occurred to think about this but seems to be a good point in favor of slotted shims.
You could probably remove the bolt safely by strapping the half shaft of back end of trailing arm forward to the frame cross member but with the spring tension just banging the bolt out and getting the end of the trailing arm lined up in place to get the bolt back in would probably be a nightmare.
Yah, I'd be lying if I said I prefer the PITA original style shims over the ease / convenience of the slotted shims but for now, I'm keeping this part of my car as OG as possible and sticking with the original style shims. Below are some pix of the shims I have (some repro stainless steel and some old and originals).
I thought about securing the front part of the trailing arm to the runway of my lift to keep the front of the TA from shooting up but I don't think the TA is going to go far if it moves at all. Here's why... The front part of the TA is surrounded on all 4 sides by approximately 4-5 inches of the frame pocket. See pix below.
SS repro shims (orig style)
SS repro shims (orig style)
Old and original shims
The TA fits into the pocket of the frame ~ 4-5 inches
The TA fits into the pocket of the frame ~ 4-5 inches
I believe the TA will twist in the pocket with the spring still attached...when that happens it will be impossible to get the shims in, along with the bolt put in..
I believe the TA will twist in the pocket with the spring still attached...when that happens it will be impossible to get the shims in, along with the bolt put in..
I believe the method to change the 2 holes shims during alignment was to get the car on the rack, see what changes needed to be made, unload the spring, remove the bolt, change the shims, install the bolt, snug it, load the spring, roll the car settle the suspension, torque the bolt, recheck the alignment. Wonder why arms and rods were bent all the time and the slotted shims came out in later 69.
1. Look at the following thread. The ratio of the trailing arm length to tire radius times the required toe change is the shim change. Then the thread goes on to describe how we did it. https://www.corvetteforum.com/forums...-distance.html
3. ALL suspension bushings MUST torqued with the vehicle at normal ride height. Assuming your're not on an alignment rack the best way to change the rear trailing arm shims is to have the car on a drive on lift. Use a pole jack to lift the spring slightly off the bottom of the spring link. That unloads the trailing arm so you can remove the nut/bolt to reshim. The last shim should be a slight interference fit and require light tapping with a hammer to drive home.
Duke
03-25-2024, 01:28 PM
Safety question: Is it safe to pull TA bolt with the car sitting on its suspension?
