wcgman

I installed roush lowering springs (eibachs) last weekend and Im starting to get a vibration at higher speeds which wasnt there before. The drop was 1" in the front and 1.5" in the rear.

No need to lecture...at about 80 to 85 is when it really picks up and then fades about 90 and by 95 its gone. Don't ask how I know.

I had no problem before the install. From what I can tell, the vibration is there above 50 as well...it just really picks up at higher speeds. I've put it in neutral and coasted and it's still there. In fact, I've turned the car off and coasted...and it's still there.

It doesnt seem to be a dangerous or heavy vibration...more like a rattle or even closer to a buzzing.

There's not much in the way of clear instructions but I know I installed the front springs on the struts correctly as they have like the bevel or whatever you wanna call it so they have to be aligned in the strut. Then on the rear, its pretty much drop the sway bar and your shocks, then just swap them for the stock. They did not look like they needed to be aligned in a specific way either.

I did not get a front alignment done yet, but the car is not tracking or pulling in any direction at all. It runs straight as an arrow.

I had 4.10 FRP installed for months with no issues. Maybe a month ago, installed axle back muffler deletes which are much louder, but no weird vibration. A week before I installed LCA's and no problems that I could detect then. Then I installed the lowering springs. I didnt detect any problems right after I installed them, but I was just having fun carving some corners. I really started to notice it when driving to work and hitting the open road.

Now...I will admit I havent done the alignment and maybe thats it...But the vibration feels like it's coming from the rear of the car. I say that because I dont feel anything coming through the steering wheel like an unbalanced wheel or something.

As far as wheels, the front tires are new, but the rear needs replaced. I have new wheels and tires on the way...

I guess my big concern is with the work on the gears and then lowering it I've somehow gone a little too far with the angle of the driveshaft going into the rear end...

Thoughts? Anybody had a similar issue?

Or...is it just lowered and now Im feeling road surfaces that the stock springs were cushioning enough my fat **** didnt know was there?

KonaStangPete

Im in no way a expert but from what i've heard anything more than an inch drop and you should get a adjustable UCA to correct pinion angle, adjustable panhard bar to recenter the rear axle, and caster camber plates to correct camber or at the least camber adjustment bolts

been looking into lowering mine as well

red96v6

Is the tightly wound coil facing up and the looser one on the axle in the rear? When I did my Saleens, I placed them in the same orientation as the stock going by the marks in the rubber pad on the axle. Just something to check...

alan0614

I have the Eibach Pros and have no issues with vibration. I am still on stock shocks/struts and LCA's. I recently did a charity track day at VIR and hit 120 on the straights and had no problems till I threw a wheel weight.

I don't know L&M's product, but you may be picking up some NVH from the LCA's. It seems that everything mod adds sounds that weren't there. Changing the PH bar will typically add NVH as well.

bakerjd

Pinion angle needs corrected! I'm willing to bet this is the source of vibration. This can be fixed by either adjustable LCAs or adjustable UCA...I have an adjustable UCA and it was a PITA to install and the location is very hard to get to. LCAs would be much easier to adjust.

BlackShelbyGt500

did you try to re balance the rear tires? same thing happened to me.

wcgman

Lots of good advice. I have a lot to check. I'm wondering if I didnt toss a rear wheel weight.

You know how these things get more confusing the deeper you delve into them...well I sat in the parking lot this morning after the car was warm and got up to 3500-3900 RPM range and could almost duplicate the vibration. Im wondering if I need to retorque those mufflers. One thing about them is there's the little key or nipple on the stock exhaust after it comes over the axle. Well, the mufflers I have didnt have the spot in the right place for that male/female to mate up. Maybe the muffler or hanger or something there is loose.

After that, I'll swap the old springs back in and if the problem is gone, then I'll chalk it up to pinion angle and get some adjustable LCA's, reinstall the Roush springs and try to figure those out. I really don't want to get into the UCA if I dont have to.

Im out of town for about 10 days so I wont be able to hit this before then, but my new wheels and tires should be here by then. I'll put those on and while Im there, torque the mufflers down if they seem loose and check the spring orientation. Failing that test, I'll

UPRSharad

I have the UPR Pro Series springs (made by Eibach to the same spec as Pro Kit) and I didn't adjust the pinion angle. I have no vibration at 130+.

bakerjd

I don't blame you...very involved install to say the least (especially if you upgrade the mount at the same time)! lol

kevinmalec

After installing my Eibach pro-kit lowering springs, I took my car to get an alignment done. I have no vibration issues driving at low or higher speeds. =-)
That maybe all that is needed.
Good luck!