Good afternoon Gents,

1999 Z28, 148k, 10k on the tires, new upper and lower control arms, outer tie rods, struts, springs, brakes, etc…

I had an alignment done twice after the suspension work was completed. I was told something was wrong with their table the first time, which is why I brought the car back. The second time, it doesn’t feel any different. It has a slight pull to the right and you have to hold the wheel at 11:30. I was told to replace the inner-tie rods as well, which they’re fine but on the list for the near future.

Anyway, the car drives fine otherwise around town on residential roads, but once it’s on the highway, it has a slight vibration that increases under load/speed. I don’t feel it in the wheel or pedal, but more just underneath my seat like the whole car is vibrating. It’s not a violent vibration by any means, just noticeable and annoying.

There do not appear to be any missing wheel weights, although I still want to get them rebalanced. I appreciate any advice that will point me in the right direction.

Thank you,

 

Has someone checked the driveline to ensure the tailshaft and pinion yoke are with 1° of each other? Driveshaft run out and balance could also be checked.

 

Thanks for the response. I have not had anything checked related to the drive shaft, but there's a shop near work that I will call. Is that a common issue on these cars?

 

It's a very common issue on lowered cars, but can be an issue on f-bodies in general. My curiosity peaked about the thrust angle of your axle now also.

 

Good to know. My car rides at stock height. Unfortunately, I made the mistake of going the Mevotech route and sourced all of the new suspension parts from RockAuto. Regardless of this newly developed vibration, the car rides harder than it did with the worn out 25 year old OEM control arms and bushings. If I could go back to last summer, I would've cleaned up and repainted the old control arms before pressing in new ball joints.

I'm also curious if the rear axle is properly aligned like you had mentioned. I didn't have a chance to mess with it over Easter weekend, but planning to rotate the tires after work today and see if that helps. If not, it might be time to take it to a different alignment shop and see if they can figure it out.

 

A quick update: I rotated the tires from front to back, took the car out on the highway and the vibration is about 90% gone. I can still feel a slight vibration behind my seat at certain speeds.

I did not notice any bulges or deformities on the sides walls or flats when the tires were off the car. There were no missing wheel weights either. Perhaps still a balance issue somehow?

 

That's fortunate, doesn't usually resolve that easily. Most of the vibration complaints show up between 70-80 mph and are a chore to shake out.

 

70-80 was about the speed I would begin to feel it. Still not 100% satisfied, but at least it’s better. I will schedule an appointment at Goodyear and see if they can rebalance the wheels and give it a quick inspection to make sure everything is as it should be.

When looking at the rear of the car, it kind of seems like the rear axle isn’t dead center like you had mentioned. There’s about 1/2” more distance from the top of the rear left tire to the left inner fender lip than the top of the right tire to the right inner fender lip.