Well, this build (1970 Cutlass) is fighting me at every step. Trying to install the rear end, using UMI tubular control arms (https://www.summitracing.com/parts/UPI-ABR813-B) and just can't get things lined up. I can install the upper and lower control arms without the springs and things line up fine. Can't get the springs in with the upper control arms bolted in, and can't line up the upper control arms when the springs are in place - just can't get enough spring compression for things to sit in the right positions I think.

What's the trick to installing the rear suspension with the body off?

 

Usually the rear springs don’t need too much compression to fit in a loose rear.
(Ha! I said loose rear)
1. Can you mount the control arms and use a spring compressor?
2. Or if you mount the upper control anrms, place the spring in and use a Jack under the pumpkin, will the weight of the frame compress the spring enough to connect the lower control arms?
Invite some fat friends over to sit on the frame?

I didn’t have much trouble doing mine a few months ago.

 

Hehehe...that's right up there with "Look under there..."

I was originally thinking I couldn't, but in retrospect I probably can. I'll give that a shot tonight.

I'm the fat friend :-D I tried sitting on the back of the frame but every time I leaned forward that removed most of the weight. Getting some friends over will be the next thing if nothing else is doing the job.

Body on or off the frame?

 

I installed the same kit in my car.
Installed the shocks on the upper mount only.
Then I bolted all the arms to the rear end and sat it on a floor jack.
I had a helper jack the rear up and I bolted the arms into place starting with lowers, then the uppers leaving the bolts snug.
Then I slipped the coil springs in clocked them into position and installed the shocks on the lower mounts. They should slip right in place.
Then installed sway bar leaving the bolts just snug.

Then I jacked the car up and placed 2 identical jack stands under the rear end and supported the full weight of the car on the axle tubes.
Then I torqued everything up.

 

This sounds like you had the body on the frame...my body's on a rotisserie so the lack of weight on the frame is contributing to my challenge! But you were able to get the springs into place with all four control arms bolted in place? I must be doing something wrong because I'm not getting enough clearance for that.

I don't think my spring compressor's arms are long enough to work on the wider rear coil springs either.

 

Success! I wound up holding the axle housing down with one foot while heaving the spring coils upwards to get them seated on their perches.

Of course, once all the bolts were in and the springs in place I realized that I needed to put some lube on the diff ear bushings, that I wanted to put the extra shims on those bushings (UMI provides an extra side shim for use in some but not all applications and hard cornering. They don't specify which applications, but state that it won't affect anything if they're missing), and that one of the lower control arms was on backward...which I was already aware of but kept overlooking while fighting the springs.

I used a couple small cargo straps to hold the spring load in place which allowed me to remove the necessary bolts (one control arm at a time!) to do the necessary tasks. I found that the aforementioned shim, which is basically a large polyurethane ring, wouldn't fit on the left side ear as the centre casting isn't symmetrical...so I have one on the right, none on the left and not gonna lose any sleep over it!

Nothing is tightened up yet...I'll hand snug them all tomorrow and wait until the body is back on before final torquing.

 

Good work!
Glad ya got it done.

 

x2