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Upper trailing arm mount problem...

1971Chevelle

1971Chevelle

Veteran Member
Senior Member
I have noticed lately that the rear differential feels like it is moving around on acceleration. Well, my suspicions were correct. The hole where the upper trailing arms mounts on the driver side
is elongate. My dad neglected the trailing arms bushings for years on this car, so when I got it, I had to get things replaced. I never noticed that hole being elongated when I had parts out, so
it may have just been slightly worn, and now it has gotten worse. I don't think there is an easy fix for this. Here are pictures of the driver and passenger side.


DSC03859.jpeg

DSC03862.jpeg
 
Fairly straightforward repair. Just note where the origial hole was and either close the worn area with weld and redrill the 1/2 inch hole....or....weld a plate over the top of it. I'd do the first option if I was worried about originality. The bars you have installed don't have the give of a factory rubber bushing or even a large diameter urethane bushing, hence the wear. The pivot points change during normal driving, that's the inherent problems you have with more restrictive movement. Unless you're on the track, I'd go back to oem bars with the urethane bushings. Even if you beef up all pivot points, you're still asking for stress issues by normal street use.
 
But you'd need at least 2 if not all 4, that'd be spendy....and you've got to address the 2 eared diff bushings.
 
cheveslakr said:
Fairly straightforward repair. Just note where the origial hole was and either close the worn area with weld and redrill the 1/2 inch hole....or....weld a plate over the top of it. I'd do the first option if I was worried about originality. The bars you have installed don't have the give of a factory rubber bushing or even a large diameter urethane bushing, hence the wear. The pivot points change during normal driving, that's the inherent problems you have with more restrictive movement. Unless you're on the track, I'd go back to oem bars with the urethane bushings. Even if you beef up all pivot points, you're still asking for stress issues by normal street use.
Click to expand...

^^^^^ Yep, what Jerry said. Pain in the ass to take apart, but welding it closed and re-drilling is the cheapest route (and the route I'd take).
 
My uppers are adjustable, with the heim joint on the body end. I have Roto-Joints on the differential housing. If I replace them, I will just
have to order some that use rubber on the body end (I will still use adjustable trailing arms).
 
Well, the problem was getting worse, so I took it to a guy today to have him do some welding. He said that both sides had elongated holes (driver and passenger), so he welded in a washer on the outer and inner of both sides (where the bolts/nuts make contact. Apparently the bolts that I had didn't have enough thread, so when I tightened them up, the bolts were actually still loose. And, my heim joints are shot.

So, I was going to just replace the heim joints with Roto-Joints, but since I don't know the thread pitch & direction, I would have to drop them both down to find out. I think I am just going to purchase upper trailing arms from UMI. There is a $30 price difference between poly and Roto-Joints. Which one should I go with? My lowers have Roto-Joints on both ends, and my differential housing has Roto-Joints. For only $30 more, I am leaning towards the Roto-Joints, as I think they will outlast the poly.
 
1971Chevelle said:
I decided to go with the Roto-Joint upper trailing arms. I placed the order late Thursday evening through Summit, and they arrived today.
View attachment 11688

View attachment 11689
Click to expand...
You just HAD to show me those…😀 do those come with any type of bushings? Or need anything where the opposite side of roto joint bolts? Another thought does roto joints allow too much side to side movement in a 4 link suspension?
 
Shovelrick said:
You just HAD to show me those…😀 do those come with any type of bushings? Or need anything where the opposite side of roto joint bolts? Another thought does roto joints allow too much side to side movement in a 4 link suspension?
Click to expand...
No side to side movement to worry about, the angle of the upper arms keeps the housing centered.
 
Shovelrick said:
You just HAD to show me those…😀 do those come with any type of bushings? Or need anything where the opposite side of roto joint bolts? Another thought does roto joints allow too much side to side movement in a 4 link suspension?
Click to expand...

They only come with the attached Roto-Joint for the frame mount. I already have Roto-Joints in my rear differential housing.
 
I have Energy Susp. in my stock upper and lower CA and lower I put a weld in plate when I had the 12 bolt rebuilt 10ish yrs ago, would those make a noticeable difference? I don’t get any wheel hop and have Lakewood traction bars that came with a rearend I bought so bolted them on
 
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