: 2002 cadillac struts replaced, now car shakes at higher speeds



benneyoboy
07-17-11, 06:59 PM
Hello everyone, this is my first post and I am desperate!
I drive a 02 sts w/109k miles. I live in MI and I am in college. I got an internship in Houston, so I drove down to Houston. When I arrived here I was told I needed new front struts by the local mechanic. I don't have much $, so I bought used original struts on ebay. They said that they would work, but now that I have them installed, the car says service suspension SYS and max speed of 90. (I think this is bec. I need to have electronic f9 struts, and the person I talked with from ebay said I didn't need the f9, and I stupidly believed him bec I gave him my VIN #). The car drives great after the new struts, but when I go over 65 or so the car slightly shakes. The mechanic says that it is either an alignment problem(they couldn't align bec of the rust i guess) or the tires need to be balanced. So, I take it to discount tire and they say the alignment is irrelevant, but I should try to balance the tires. I balance the tires and nothing changed. The tires are about 6 months old and this shaking problem I did not have until the new struts were installed. Does anyone have any clues/advice/ anything. I need to get home to Michigan in a few weeks and I do not feel comfortable driving on the freeway with the all vibration.

Submariner409
07-18-11, 09:33 AM
Several things - Look at the car's build date on the driver's door sticker - the tire rating sticker. If the date is after 01/02 the car takes VERY different struts from the earlier versions.

Highway vibration after suspension work is usually due to wheel runout and/or tire balance. Wheel runout is caused by dirt or rust chips between the hub and rotor or between the rotor and wheel. Those 4 mounting surfaces must be absolutely clean and smooth, with the lug nuts (remove the decorative caps first) torqued to 100 ft/lb in a crisscross star pattern. If all is squeaky clean and torqued properly, then you might invest in a Hunter Road Force balance job. NOT cheap. Otherwise, suspension arm bushings, upper strut mounts/bearings, sway bar bushings, tie rod ends.

The service suspension and speed limited messages are due to the original suspension control circuits not being either connected properly or because of the improper struts. The suspension control system MUST "see" the proper wiring resistances and control feedback. Do some snooping in Discussions, item Specific: Cadillac Tech Tips (near here) to find suspension message workarounds.