Trailing Arm Bushings

[Joe L.]

Re: Trailing Arm Bushings

I bought these at a swap meet for $.50 ea, the rubber looks normal and there is surface rust on the bushing housing. Are they OK to use, the box is probably from the 1970's.

Timothy------


I think they'll be fine. However, I'd clean off the rust with a wire wheel, especially on that part of the bushing that is an interference fit in the trailing arm.

[Timothy B.]

Re: Trailing Arm Bushings

Thanks Joe,

I was going to dust them off a little with a glass beader but your idea may be better.

[Thomas F.]

Re: Trailing Arm Bushings

Do the newer vehicles use urethane bushings or rubber?

[Thomas F.]

Re: Trailing Arm Bushings

Here is my trailing arm story. I decided to have a 4 wheel alignment on my 69 Vette. To make alignment easier for the alignment shop I decided to use the slotted stainless steel shims. At this time I did not realize the slotted shims required a big cotter pin thru the holes in the opposite end. My 69 trailing arm did not have holes for this cotter pin. The alignment shop used the slotted shims I provided, but they did not realize a cotter pin was necessary to keep them from coming out. So....one day on the interstate my car got really difficult to control and I had to drive back home very slowly where I realized I had lost some shims. After doing my homework I drilled a hold in my trailing arms and replaced the missing shims and cotter pins. This is when I decided to rebuild my trailing arms and use urethane bushings. All was well until the passenger side trailing arm bushing crumbled like a cracker after several years. Why it broke apart I will never know. Maybe I did not install it correctly although I was very careful to do it right or maybe it was just junk to start with. I hope the other one holds up. Thanks to all who participated in this thread. Just make sure if you have slotted shims you have the cotter pin to keep them from falling out.

[Joe L.]

Re: Trailing Arm Bushings

Do the newer vehicles use urethane bushings or rubber?

Thomas------


As far as I know, rubber is used exclusively even in modern day cars.

[Joe L.]

Re: Trailing Arm Bushings

Here is my trailing arm story. I decided to have a 4 wheel alignment on my 69 Vette. To make alignment easier for the alignment shop I decided to use the slotted stainless steel shims. At this time I did not realize the slotted shims required a big cotter pin thru the holes in the opposite end. My 69 trailing arm did not have holes for this cotter pin. The alignment shop used the slotted shims I provided, but they did not realize a cotter pin was necessary to keep them from coming out. So....one day on the interstate my car got really difficult to control and I had to drive back home very slowly where I realized I had lost some shims. After doing my homework I drilled a hold in my trailing arms and replaced the missing shims and cotter pins. This is when I decided to rebuild my trailing arms and use urethane bushings. All was well until the passenger side trailing arm bushing crumbled like a cracker after several years. Why it broke apart I will never know. Maybe I did not install it correctly although I was very careful to do it right or maybe it was just junk to start with. I hope the other one holds up. Thanks to all who participated in this thread. Just make sure if you have slotted shims you have the cotter pin to keep them from falling out.

Thomas------


I don't know why you had to drill a hole in the trailing arms in order to install the shims or retaining cotter pins. The only holes required are those in the frame and you say your car had those.

I can tell you this. I drove my 1969 for way over 100,000 miles with slotted shims, not tucked down into the frame pocket, and without retaining cotter pins. I NEVER lost a shim. If the slotted nut is properly tightened to specified torque and the nut's cotter pin properly installed, there won't be a problem.

[Duke W.]

Re: Trailing Arm Bushings

All was well until the passenger side trailing arm bushing crumbled like a cracker after several years. Why it broke apart I will never know.

Failure was inevitable in a relatively short time. See post #5 for the reason.

Duke

[Duke W.]

Re: Trailing Arm Bushings

Thomas------




I can tell you this. I drove my 1969 for way over 100,000 miles with slotted shims, not tucked down into the frame pocket, and without retaining cotter pins. I NEVER lost a shim. If the slotted nut is properly tightened to specified torque and the nut's cotter pin properly installed, there won't be a problem.

Also, it's IMPORTANT that there is a very slight interference like the thickness of one 1/32" shim. The last installed shim, a thick one, should required slight tapping with a small hammer to install. and the bolt should be torqued at normal ride height.

My SWC has slotted shims and no castle nut/cotter pin like other '63s, and I never had a problem with loosing shims. The later designs with captured shims or slotted shims retained with the big cotter pin through the frame is a more "fail safe" design, but if the shims are properly installed and the bolt torqued properly as described above, lost shims should never happen.

Duke

[Leif A.]

Re: Trailing Arm Bushings

Also, it's IMPORTANT that there is a very slight interference like the thickness of one 1/32" shim. The last installed shim, a thick one, should required slight tapping with a small hammer to install. and the bolt should be torqued at normal ride height.

My SWC has slotted shims and no castle nut/cotter pin like other '63s, and I never had a problem with loosing shims. The later designs with captured shims or slotted shims retained with the big cotter pin through the frame is a more "fail safe" design, but if the shims are properly installed and the bolt torqued properly as described above, lost shims should never happen.

Duke

Educational question Duke. Exactly how does one torque the bolt when the car is at ride height? I understand that this is the procedure but how do you get to the nut with a torque wrench with the wheel and tire in the way?

[Joe L.]

Re: Trailing Arm Bushings

Also, it's IMPORTANT that there is a very slight interference like the thickness of one 1/32" shim. The last installed shim, a thick one, should required slight tapping with a small hammer to install. and the bolt should be torqued at normal ride height.


Duke

Duke------


Yes, absolutely essential.

[Larry M.]

Re: Trailing Arm Bushings

Educational question Duke. Exactly how does one torque the bolt when the car is at ride height? I understand that this is the procedure but how do you get to the nut with a torque wrench with the wheel and tire in the way?

Leif:

It's called "gut feel" Agree getting a torque wrench in there would be difficult at best. But most of us know what 40-50 ft-lbs feels like, plus you have to also go far enough to line up the cotter key. So most (or all) of us just "wing it" as best we can.

Larry

[Thomas F.]

Re: Trailing Arm Bushings

Thanks Joe for your reply. Sorry I was not exactly clear in my post. I did not drill any holes in my trailing arms. I drilled the holes on each side of my trailing arm pocket thru the frame. There were no holes there since my car is a 69 and the slotted shims were not being used at that time. I am glad you have not had any problems with your shims. It must have been a concern with GM in later years when they went to slotted shims or there would be no cotter pins installed or there would be no holes in the shims for the cotter pin to go through. Another concern I have is the torque required on the trailing arm bolt. Do you think this bolt actually compresses the frame against the shims? Is the frame that weak? I know the cotter pin in the bolt is important to keep the nut from coming off and the torque is probably important to keep the bolt from turning. I would guess your shims were installed tighter than mine. Mine which were tucked down inside the frame did come out and gave me a scare. Anyway I feel a lot safer with the cotter pin installed through the shims. I'm not sure when the slotted shims came into use. I believe in 70 or 71. Maybe the AIMS of these years would be helpful. Thanks again Joe for calling this to my attention. I appreciate all your posts you have help me many times.

[Leif A.]

Re: Trailing Arm Bushings

Leif:

It's called "gut feel" Agree getting a torque wrench in there would be difficult at best. But most of us know what 40-50 ft-lbs feels like, plus you have to also go far enough to line up the cotter key. So most (or all) of us just "wing it" as best we can.

Larry

That's what I've always done Larry. Twisting wrenches (even though just for a hobby) for 50 years you kind of get a good "feel" for what's right. I was just curious if someone had actually figured out a way to get a torque wrench in there. Thanks for your kind response.

[Joe L.]

Re: Trailing Arm Bushings

Thanks Joe for your reply. Sorry I was not exactly clear in my post. I did not drill any holes in my trailing arms. I drilled the holes on each side of my trailing arm pocket thru the frame. There were no holes there since my car is a 69 and the slotted shims were not being used at that time. I am glad you have not had any problems with your shims. It must have been a concern with GM in later years when they went to slotted shims or there would be no cotter pins installed or there would be no holes in the shims for the cotter pin to go through. Another concern I have is the torque required on the trailing arm bolt. Do you think this bolt actually compresses the frame against the shims? Is the frame that weak? I know the cotter pin in the bolt is important to keep the nut from coming off and the torque is probably important to keep the bolt from turning. I would guess your shims were installed tighter than mine. Mine which were tucked down inside the frame did come out and gave me a scare. Anyway I feel a lot safer with the cotter pin installed through the shims. I'm not sure when the slotted shims came into use. I believe in 70 or 71. Maybe the AIMS of these years would be helpful. Thanks again Joe for calling this to my attention. I appreciate all your posts you have help me many times.

Thomas-------


My 1969 had the holes in the frame for the cotter pins. Late 1969 had the holes; early 1969 did not. My car had a mixture of slotted and non-slotted shims but no cotter pins were ever originally installed. The generally recognized initial use of the slotted shims was 1970.

[Duke W.]

Re: Trailing Arm Bushings

On a four post drive-on lift use the Corvette's scissors jack to just contact the frame rail ahead of the rear axle, which is the normal jack point for changing a flat. Then use a "pole jack" to raise the spring just enough to remove the load and manually raise the trailing arm enough to remove the tire. Filling the tire to high pressure helps. Then you can remove the nut/bolt, change the shim pack as required and reinstall the bolt and torque to spec.

Duke