I just saw a post on FB where a guy installed a rear sway bar on his '70 Cutlass. He mentioned that he torqued it down with the weight of the car on the rear.

When I installed mine, I seem to remember torquing it down while it was still on jack stands. Does it make a difference?

 

Probably not on the sway bar as long as the rear is level.

 

I prefer it to be torqued with the weight on the wheels on level ground.

 

I ASSume the jack stands were on the frame. That would not be my preference. IMO any suspension final tightening should be done with vehicle’s weight on the suspension. For sway bars, as previously mentioned, it probably is no big deal but I would still have weight of car on suspension.

​​​​​​….

 

What matters is that the two lower control arms are parallel. It doesn't matter if they are hanging down or if the suspension is loaded, so long as there's no twisting of the axle relative to the frame. Torquing the suspension bolts with the weight on the wheels only applies to those bolts that trap the rubber suspension bushings in the "unloaded" position. This means the four front LCA bolts, the four nuts on the front UCA cross shafts, and the eight rear suspension bolts. The other ones that matter are the four bolts that hold the FRONT sway bar bushings to the frame. Nothing else will matter.

 

"Eight rear suspension bolts"...are you referring to the control arm bolts...more specifically, the ones that bolt the LACs to the rear axle housing?

 

There are eight bushings, one at each end of each rear control arm. Each bushing has a bolt. That's eight rear suspension bushing bolts that need to be torqued with the rear suspension at ride height.

 

Gotcha...and what happens if you torque them with the rear suspension unloaded?

 

The car may sit higher and the bushings may get damaged.

 

^^^This

The bushing is a rubber torsion spring. When you torque the bolt, it clamps the center sleeve in one position relative to the outer shell. As the suspension articulates, the outer shell moves with the suspension arm, which causes the rubber in the bushing to distort. By design, the rubber is supposed to distort relatively equally in either direction with the bolt torqued at normal ride height. If you torque the bolts at full suspension droop, the distortion is always in one direction and about twice as much angular movement as designed. This overstresses the rubber and leads to early failure.

 

Makes sense...I wish I could remember if I had the cat up or on the ground when I tightened everything up...

 

If you are uncertain, you should probably start over with the proper technique.

 

Yeah Norm, that's what I've been thinking, but it's been a while since I installed the sway bar. Wouldn't it seem that if there were any issues, I'd notice them by now? Plus, if I had done it wrong and tightened them up with the car lifted, then the rear ride height would be different when I set it down, correct? I ask this because it's the same as before I installed the sway bar.

 

Ride height same? Perhaps. Depends - I couldn't say unequivocally. If you torqued them in the air on jack stands, when you lower the car and put the weight of the car on the bolts/bushings, you're placing significant stress on the hardware (bolts/bushings). Bolts/Bushings will then want to rotate when you set the car back on the ground imparting unyielding stress to both the bushings & associated hardware because essentially you locked (torqued) them in place with no weight on them. Make sense?

I mean, honestly, Joe said it spot-on, mine is just a different manner of stating the same.

 

So here's a video demonstrating the "basic" idea. Obviously, this is a front-end control arm. But basically the same principle applies. See what happens at the 2'20' time period in this video. Actually, watch the entire preload idea in the video noting this is front end control arms.

 

I re-read your last statement and noted you are talking specifically with regards to the sway bar? This makes no difference regarding the rear sway bar, as Joe previously noted. It does make a difference on the front sway bar, as noted previously.

Whether you torqued the rear sway bar with or without vehicle weight on ground makes no difference.

 

I watched the video Norm...good stuff. I need to elaborate though. I started this thread about the rear sway bar, then Joe mentioned the rear control arm bolts, and that's where my dilemma is. When I refreshed the bolts that hold the rear LCAs to the rear axle housing, I can't remember if I torqued them down before or after I lowered the car. 🤔
As I mentioned in post #13 above, it's been almost 2 years since I did the work on the bolts, so it would seen that I would have encountered an issue if I didn't preload the bushings, correct?

 

Understand, Dave. I might (should) have instead simply stated "No" it makes no difference, but thought I'd toss up the notion of the torque sequence of bushings as a visual. At any rate, as several members have stated and eluded to, it makes no difference if it's in the air or on the ground when you apply the torque to the REAR sway bar so long as stated below by Joe.

Which is just like Randy & Eric were suggesting - the axle is even (level) or on the ground (assuming the ground is level) when you install the REAR sway bar. If the rear LCAs are not parallel, you'd have a situation I'd call "cattywumpass" (disorderly, awry, askew, or incorrectly).

 

I'll bet there are many instances of some mechanics and DIYs who torque these bolts incorrectly without noticeable effects by the driver of the car. Probably half of them didn't "torque" them to begin with - on the ground or in the air. Add to this the variations in manufacturers of the (hardware) nuts/bolts & bushings - rubber vs. polyurethane, etc. There are pros & cons to both sets of bushings (rubber vs. polyurethane). At this point, if you want to be **** about it, jack the rear end off the ground, use a flashlight and get up close to the bushings - do you see any cracks, wear & tear, etc.? It doesn't take too long to loosen the bolts and re-torque on the ground.

 

Good info in this thread. Now I need to go back, loosen my front anti-roll bar at the frame, and re-torque while sitting on the wheels.

 

We're here to help.

 

No cracks or otherwise, and I loosened and re torqued them yesterday, this time making sure I did it correctly 👍 😀

 

Nice job, Dave. 😉😁