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At 70 mph and faster, I'm getting a strong vibration. It's so bad the sun visors shake. Doesn't happen at lower speeds or at idle. Car has these wheels on it now:
245/45/17 Michelin Pilots on Race Star 15x10 set at 32 psi
275/50/15 MT e.t. streets on Race Star 17x9.5 set at 25 psi
I'm getting ready to install more stuff both OEM and aftermarket on this car. Some for performance reasons, some because it makes sense to replace while I'm in there, and some because I simply want an aftermarket suspension component that is red instead of black. So here's what all I'm replacing:
Inner and outer tie rod and boots (MOOG EV260, ES3238RL, 913101R)
Front hub assemblies (Timken 513090)
Both knuckles (has some rust, they are coming out for red powder coat)
Front sway bar - remove
Rear sway bar - red aftermarket
K-member upper lower a-arms - red aftermarket
Motor mounts - prothane
Rear adj control arms - red aftermarket (replacing non adj)
Tunnel mount Torque arm and cross member/loop - red aftermarket
Installing SE 1 7/8 long tubes and their matching Y pipe with 33272 clamps , c7 front brake setup (pads, rotors, calipers), fresh spark plugs, and a ATI 10% balancer with an ARP bolt.
The rest of the suspension that won't be getting replaced that's already on the car:
Viking double adj coil over kit, front and rear
Moog Front Upper Strut Mount Kit and strut mount assembly
Adjustable Red Spohn Panhard bar
Red BMR Weld in SubFrame Connectors
Car has an S60 rear and a PST 3.5 balanced driveshaft. Well, at least I was told by PST that it was balanced and they are top notch but I'll recheck it. I'm hoping that after I install the new parts, I will have inadvertently stopped the vibration at speeds above 70 mph. All lugs torqued to same spec. I'll start digging further and make sure every last bolt is torqued down to spec along with checking:
Wheel balance
Check for warped wheels
Road force balancing, make sure the reading is "20" or less
Alignment
Transmission mount ACDELCO 22174970
Recheck driveshaft balance and u-joints
Recheck pinion angle. S60 it is best to set pinion at 0 degrees. I'll use UMI method to do this.
Transmission tailshaft bushing 6260048. Not sure on part number for Rockland bushing for 4l60e?
If it's the flexplate / converter then the vibration would be there in neutral as well as in gear, I would think. In neutral at same RPM as 70mph and higher, no shake. I'm going to try putting it in neutral and coasting down from 80mph to see if it still happens.
Looking at these parts diagrams, I'm hard pressed to find something that IS NOT getting replaced or has not been replaced with either aftermarket or a new OEM part. While all this is getting torn apart, am I missing anything that I should do?
Last edited by 5.7stroker; 08-18-2017 at 09:41 PM.
I did. The first thing I did when I had this issue is search for vibrations at high speeds. I'm replacing almost everything in the suspension for other reasons, so I'm sure the issue will resolve itself. Problem is I won't know what caused it as I'll be replacing many things at once.
I have a friend who got tires road force balanced a few times over the years (part of the install service included when you go to Tire Rack), and he has always needed to have a local shop do a standard spin balance afterward because it always vibrated at high speed. This was Just one guys experience though; food for thought.
08-13-2017, 12:45 AM
Vibration on highway? 
