Does this affect lowered cars only? I just bought some BMR springs and I was wanting to install them, but after hearing this I don't know what to do. Any suggestions guys?

 

Wow! I thought I was the only one! I installed Eibach Pro-kit, Mufflex 4" exhaust, Spohn Adj (body mount) torque arm along with LCA's and LCA Brackets, Adj Pan Hard Rod, New rear-end bearings (all) GM 4.10 gears, U-joints, Haven't balanced the driveshaft yet, New Fikse wheels/BFG tires all balanced and Textralia clutch. I made too many changes at once so my diagnosis is a little tougher,but right now I'm suspect of the energy suspension trans mount, I felt a lot of vibration when I installed it and since I went to a body mounted torque arm I'm gonna install the stock one( trans mount) back in, or shave and/or eliminate the spacer on the poly mount! I believe as someone mentioned the Poly mount may throw off the pinion angle so I'll have to recheck the angle and hopefully find something. I'm leaning towards doing the motor mounts also.Although it's all new(10 bolt) the rear end would be my next suspect, Pinion yoke, bearings, gears, etc.. hopefully not but possible ! The exhaust also may be a culprit but not sure!Like I said it's tough because of the many changes at once! I'll keep ya posted just like I hope ya will too! Going past 70 (although I don't often do that) has become a challenge, but I will fix that!

 

Awesome guys lets keep this up!

Oh and if someone has a host for a 38 meg quicktime vid, i have one and we can confirm if its the same vibration...

 

im crossing my fingers that the adj TA and checking over my rearend will fix my problem. I dont think its a problem with just lowered cars though....there has to be something that when you drive these cars hard something wears or fails. Which would point to something like bearings or U joint failure.

However, a lot of people who have lowered the car or swaped their rearend for a 12bolt, diff tranny mount, ect.... seem to have the similar vibration problem which could point to throwing off the rear suspension geometry being the problem. All i know is i hope we can get it fixed.... instead of making me happy when i drive my car it just pisses me off and i know the rest of you feel the same

 

TTT... I want to keep this thread up and going until we figure it out. Lots of good ideas and info so far.

An update on my situation. Last Wed I had a new clutch/fly installed. That took care of some of the vibration. When the installer drove the car after installing it he said that the noise/vibration I'm getting can be expected with the type of suspension and T/A I'm running. I understand and expected that. With poly/rod end combo LCAs, PHR and the Spohn body mount T/A I know I'm going to get more noise, and maybe a little vibration, but it shouldn't be this bad. I'm going to play with pinion angle some more as that seemed to help. I'm also considering rotating my drive shaft 180* as well as checking the balance on it. I'm really dreading the fact that within the next couple months I will be H/C and maybe a small shot. I plan on launching off the spray at a high RPM with slicks...that combined with my M6 would spell death for the stock aluminum DS. I'm going to have to have an aftermarket piece. I'm hoping a high quality like the Denny's Nitrous Ready shaft will be OK. I know it will with the shock/load/power, I hope it's alright in the vibration dept.

 

When I first bought my Trans am it had the wom wom wom ... i got a modified rebuilt aluminum driveshaft.. the guy said he removed the balancer.. but told me it should be fine without it. After getting it installed the vibration was reduced but the wom wom wom still there. I am going to do the torque arm next followed by new gears and bearings. There is so many variables this is really frustrating.

 

If youre doing those soon, lets us know how it goes. Thats pretty much what it is is a wom wom wom

 

My car is not lowered yet. The rear end was new, the clutch is new, the drive shaft is new (and u-joints), the torque arm is new. Changing to the steel drive shaft made the vibration worse even though it was rebuilt and balanced by a very reputable shop. Right now the vibration comes on around 70-75mph and increases with speed at least up to 110mph. At first, it came on at 45-50mph. Things I've done to help are: replace pinion yoke which was out of tolerance (should be less than 0.002 total indicated runout if I remember right), adjust pinion angle (still trying different adjustments), rebuilt steel drive shaft with new joints (balanced), added rubber material under body attach points, straightened torque arm so I didn't have to force it into position.

Regarding pinion angle, it seems like we should be explaining how we do this as there are several different techniques out there. I measured the front of the crank pulley and the back of the trans and they both measured -2 degrees (higher in front than back). My drive shaft measures
-3.5 degrees. I currently have the pinion set to match the trans and balance the front and rear drive shaft u-joint angles (just did this now for a test). That gives me 0 pinion angle relative to the crank axis or -1.5 degrees pinion angle according the the directions from Spohn (DS-P=PA). I'm going to try this and then adjust to -0.5 degree pinion angle according to Spohn and test again. Back later with results.

 

I've driven several F-bodies...some with only a lid and FTRA they all had the wom wom wom to one degree or another. The thing with mine now, is that I don't hear the wom wom wom. Now it's a vibration I feel. Although I'm noticing that as the vibration is getting a bit better as I'm wearing the new parts in. I have to go out of town for a couple weeks on Friday, but I've got some ideas to try when I get back.

 

Ok, back from the dead here we go again......

So now this problem has me completely stumped again. Last time i was on the highway driving around 80mph i noticed the rpms were roughly 2100....so the other day while driving around in town i pulled the shifter down from OD to either D or 2 i fogret, but the point is i got the rpms to sit at rouglhly 2100 again, but i was probably only going 55-60mph. I noticed when i did this that it seemed as though the same vibration was occuring, but to a lesser extent. It wasnt quite as bad as it is when 80mph+ but it was still somewhat there. So here is the problem. I understood that if the problem varied with speed that it was probably related to driveshaft problem or rearend problems......now i think it might have something to do with rpm as well, so i guess that opens the door for a whole new list of possiblities....anyone have any ideas of what could cause vibration thats rpm related.....i know exhaust is one possibility, although i never had a problem with it before...but what else ?

 

wom wom wom without vibrations is a problem with the bearings somewhere in the rear end; might as well replace em' all while you're in there - wheel (axle), pinion, and carrier bearings. I did it and got rid of the noise, but I still have a slight vibration. (yes, I'm lowered)

 

We seriously have the exact same **** goin on!

 

im not having any problems, yet. has anybody checked engine vibration. maybe a slight miss, or worn eng mounts. check all bushings for wear and tear, grease ball joints and front + rear suspension. maybe a brake shoe hanging up. just figured i would give some suggestions. hope it helps

 

Ok, well, heres my story. i got terriable vibration in the highway at aroung 60-80mph, but only betwee 2000 and 3000 rpms, if i mashed the throttle it would go away (or i noticed it less, idk which). well i replaced my front shocks with bilstein hds, n change. i finally got around to getting hte back ones in last night and i also lowered my tire pressure to about 32psi all around. the vibration is gone... i hope at least as ive only driven it on the highway once..check ur tire pressures, i had mine set to 40+ (as the tires say max psi 44.. stupid me. think about it, if ur running tires with high psi, there is so much extra weight spinning at high rpms, lower it and seeif that makes a difference (though it might be the rear shocks...)

 

Ahhhhhhhhhhhhhhhhh!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Ok, I feel better now.

 

Ummm,that's more common then you'd think. A friend of mine bought his wife a PT Cruiser and he runs 44PSI in her tires because.....yep, you guessed it, that's what it says on the sidewall. This guy is an engineer for Chrysler, too!! Some people.

 

Usually vibrations that are rpm related are due to an unbalanced clutch/pressure plate. In any case, it has to be something that was changed on the engine.

 

Yes. It can also be a bad rear u-joint or a pinion angle that needs adjustment.

 

I ran up to 110mph last night with pretty minimal vibration. Last summer it felt like something was going to fall off just doing 60mph. That was after a 9 inch, steel drive shaft and Spohn torque arm installs. Here's what I've done to fix it so far...

Drive shaft professionally rebuild and balanced w/ new u-joints ($400 that didn't help).
Replace pinion yoke with billet unit ($125 that helped a lot).
Adjusted pinion angle from -1to -3 in half degree increments (helped little).
Added adjustable PHR and centered rear ($110 that helped a little).
Pulled torque arm and tweaked it a bit so it would fit perfectly with no bind (had to pry on it before to get it to line up) and added rubber spacers at cross brace mounts (helped a little).
Lowered car by roughly 1.5 inch (cut stock springs) and re-adjusted pinion to 0 degrees (helped a lot). With the car at stock height (my front wheel wells were 28+ inches) and the Ford 9 inch, I had u-joint angles at the edge of acceptability.

The last thing I want to try is to tie down the exhaust system a little better using rubber isolators and see if that helps. I have two bullet mufflers in the I-pipe and have noticed I get some vibration there. Beyond that, I know I have a Michelin Pilot Sport tire that has somewhat of a flat spot (so much for buying "the best") which causes some vibration. I'm about ready to declare victory on the vibration and go racing.

 

EXCELLENT post!