Spring Replacement

oldsmobile
silhouette

#1

I need to put new rear springs into my '00 Silhouette (133K, new rear shocks went in at about 115K). They are coil springs and I have air leveling suspension.



Part 1: I can get either constant or variable rate springs but I don’t know the difference in how they will ride. I want what everyone wants - good handling, a nice soft but firm ride with minimal body pitch & roll along with good load carrying when I load it up. (It spends most of its time unloaded and I don’t want it to ride like a pickup truck, but I also don’t want to worry about it when I load it up for a trip).



Right now the original springs, IMHO, give too much body sway & roll but I bought the van used (at about 100K) so I don’t know how much of that is in the OEM design and how much is just old springs. I also can’t figure out for certain whether the OEM are constant or variable - eyeballing them on the van they look like constant rate springs. I do know I don’t want to feel like the whole van is leaning over whenever I corner.



Part II: My Haynes makes no mention of the need for a spring compressor - you just jack it all up, disconnect the lower shock mounts & track bar, and lower the rear suspension until all of the load is off off the spring. Is it this straightforward or am I smarter to use something like a compressor?



Thanks.


#2

You can determine if the spring rating is constant or variable by looking at the coils on the spring. If the coils aren’t equally spaced it’s a variable type spring.

To remove the springs, raise the rear of the vehicle as far as possible and then support the vehicle by the frame so the rear axle hangs. Place a floor jack under the rear axle and support the axle. Remove the bottom shock bolts. Slowly lower the rear axle until the rear springs are out of compression. Remove the springs. Reverse for reinstallation.

Of course, check for brake hoses, cables or anything else that might be stretched while lowering the rear axle.

Tester


#3

Some vehicles can be done without a spring compressor. If you jack it up until the wheels are off the ground and then disconnect the shock, you will get a surprise. You can disconnect the shocks and trackbar first, then jack it up or jack it up and put on jackstands, then jack up the suspension right under the spring to be replaced, undo the shock and trackbar, then let the jack down slowly.


#4

Never having worked on a Silhouette, I can’t comment on the need for a spring compressor (I’d want to have some on hand). But I can explain the difference between constant and variable rate springs. And add some other thoughts.

Constant rate springs will become firm in a linear manner in direct relationship to their compression. As you compress them, they become harder at a consistant rate. Visuall, the coils will be all the same diameter and spacing from end to end.

Variable rate springs will have a “softer” rate at the beginning, but them stiffen up as they’re compressed. Typically the provide a more comfortable ride. Visually, the spacing and/or the coil diameter will very as the windings get toward one end. It’s that variation that creates the variable rate.

Springs really don’t wear out in ten years. in 30 or 40 years they can sag, but yours should still be good unless they have broken coils. For body roll, you might want to look into aftermarket antisway bars. They’ll do more to control body roll than new springs.


#5

If you jack it up until the wheels are off the ground and then disconnect the shock, you will get a surprise
Right - I get the part about supporting the rear axle while in the process.

Thanks to you & Tester - that matches the basic thing in my manual and by looking at it, it seemed right to me.


#6

Thanks mtnbike - I will actually have the van into my alignment/tire shop Friday (this all started in part b/c I’m going to get new tires). Right now I know that the driver’s side sits lower than the passenger’s side - not by a lot, but I’ve also got what appears to inner edge wear on the rear tires and have had some out of the ordinary jouncing over certain kinds of bumps recently. I plan to have them inspect it all, check the alignment and advise, but my preliminary guesses say that I might be happy to have new springs back there.
Additional anti-sway equipment aside for a moment (I may look into that), springs will play some in body roll. Would there me a difference between constant & variable? Getting the difference as you described it I can see it going either way. Or are either of these designs superior to the other for normal everyday family-type use?