I've been troubleshooting a heavy vibration in my 01 SSM6 for a little over a year now. I've been deployed and in and out, and didn't take it on the interstate much until the last year when I noticed it.

I've done a lot of reading from previous threads on this issue, and so far nothing checks out.

First, explanation of the vibration; Approximately above 70mph+ the car begins to vibrate internally. I wouldn't call it severe, but it's pretty annoying. It is mostly noticeable on the steering wheel, shifter, and the door panels. It occurs in any gear, not just 5th or 6th and neutral (theoretically ruling out the transmission) It's not intolerable for driving, but I wouldn't want to take it more than an hour away due to the pure annoyance.

What's been done. (Car was lowered)
Wheels/Tires balanced, and re-balanced again to double check.
Adj. LCA's, Adj. Panhard, Subframe connectors, Adj. Torque Arm.

We have the driveline angle set to -2* from the crank pulley to the axle, which is the last advice I read on here somewhere. At this point, the next thought is maybe the driveshaft, but I'm at a loss currently.

Thoughts?

 

FWIW...

I had a vibration that would start at about 50mph and not go away all the way to about 75mph....but was really bad....so I would always slow down. Did it in neutral also...

My fix....new tranny mount. The bushing was shot. We assume it was putting my pinion angle out of limits.

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OP

if this vibe was not there before you did the suspension mods (lowering car and adj control arms) than sounds like your drive line angle is not right

Did you also put in lower rear end gears?

 

Car was lowered before the other mods. Driveline angle was set a week ago and still has the vibration. I haven't touched the gears. I was planning to do a full axle swap at some point down the road.

 

No other ideas?

 

Rear axle. Pinion bearing gone?

 

Is there a good way to test that theory?

 

Can you explain how you did this? Did you measure trans angle and then pinion angle to find your working angle?

 

Have you watched this video

 

Took it to the shop and let the mechanic do it. lol

We used a digital accuMASTER digital angle finder and level.

Also, I have watched the video. That (and reading here) is how I figured out that my pinion angle was off in the first place.

 

I have a vibration that I been chasing too. Just like you I have balanced, rebalanced, switched rims, switched tires. Tried different driveshafts, new u-joints.

Everything helped a little. Biggest difference was when I chucked the poly trans mount and went back rubber. I feel my vibration in my seat.

Another huge difference was with UMI adjustable torque arm. When I had the rear fluid changed I had metal shavings on the magnet.

FYI suspension is all rebuilt.

I talked to Sam Strano and he suggested pinion bearing.

I have a new/used rear with 30k miles going in mine and going to set the pinion angle.

I am not sure how critical pinion angle is, but if you consider for the moment that the car has a trunk and rear seats that if loaded could add approximately 3-400 pounds easily and change the pinion angle.

I think the pinion angle has to be way off for it to be the issue in my case, perhaps in yours as well.

All my efforts have pushed the vibration up in MPH. It is slight at around 90mph. I believe it tends to go away at around 110mph. Logic would indicate that since the rear is under load that the pinion doesn't have as much play???

But I don't claim to be an expert. I just play one on the inter webs.

 

I've read adjustable torque arms are not worth the hassle they can cause. If you have a stock rorque arm you might want to switch back to it

 

The problem was slightly worse under the stock torque arm, and it had the pinion angle out of tolerance.

 

so have you checked your driveshaft if it's balanced?

 

Long shot but what carrier are you using? I installed a new Auburn once and it was way out of balance, shook the rear badly.

 

You've got me on what a carrier is.


I haven't been able to check the driveshaft itself yet.

 

I had my mechanic (drive) spin the wheels while on a lift. The driveshaft and my rear axles were both wacked out. It is getting fixed now.

 

Maybe at some point the DS got hit and now has some runout. With rear end of car raised and suspension loaded you can watch DS rotate or use some form of feeler for runout

U joints could also be going out

with suspension mods and lowering the DL geometry is off and sometimes adjusting it to "stock" specs may not resolve vibrations caused by errant DL angles. Maybe try -1

when the shop did adjust DL angle...what was it before they made it -2?

 

Factory ds angle is 0. After I put on my mid mount torque arm I got noise/ vibration until I put angle back to 0. Now I just get a little noise above 60 but no vibration

 

Unsure the first time. Second time it was +4 something.