FBOMB90

I have a 1990 T/A that I have upgraded almost all of the suspension on. UMI wonder bar, crossmember, rear solid lower control arms, relocator brackets, solid panhard bar and strut tower brace. KYB shocks, eibach sportline lowering springs. Since I've installed these parts I've noticed a driveline vibe from 60 MPH and up, getting worse the faster I go. I've heard from a lot of people that lowering the car and consequently changing the pinion angle will cause this vibration. I've also heard that I should have purchased an adjustable panhard bar not a solid one. I don't drive the car much but love to DRIVE it when I can! This vibration makes the car undriveable @ high speeds. Is it true that I can fix this issue with an adjustable torque arm and panhard bar? I really don't want to waste my money if I don't have to. Just as an added note, I have replaced the U-joints recently so I know they are good.

JamesC

iTrader: (5)

Did you swap in a poly mount with the cross member? If so, that may well be the problem.

JamsC

FBOMB90

Yes I did, but how would that cause a vibration @ high speeds? Too tall? Or too stiff?

JamesC

iTrader: (5)

Some members have experienced issues with the poly mount. Check the info in the following link before spend any large dollars:

https://www.thirdgen.org/forums/tran...ison-pics.html

JamesC

scholtmj

iTrader: (3)

An adjustable PH bar and TA are a must with a lowered car.

FBOMB90

I've only put about 100 miles on the car this year but really want this issue fixed! It's off the road for the winter and I will try the trans mount adjustment in the spring. Thank you for the advise. I know the vehicle has to be aligned since I've lowered it, that too will be done in the spring. I hope to have an adjustable panhard bar and torque arm by then as well so I can make all of the proper adjustment while I have it on the alignment rack. I really love this car and accept that it will forever be a tough relationship to endure!

BMR Tech

Lowing your car will always alter driveline angle, that's how it works. It's usually marginal, but your car could have been close before and pushing it down has generated a vibration. So, more than likely, your pinion angle is off now that you've dropped the rearend higher. A solution to this is to install an adjustable torque arm. This will allow you to properly correct that problem. However, the first thing I would check is your torque arm bushing up front. Make sure that is in ship-shape. Because if that bushing fails and the torque arm is allowed to wander, it can throw off the driveline angles.

As for your panhard bar, yes. You should have purchased an adjustable panhard so you can shorten it and bring the rearend back to square underneath the car.

- Kevin

BlackenedBird

iTrader: (5)

Yes on the APHB but not so on the adjustable torque arm. I've had many lowered 3rd gens & not once have I ever had an adjustable torque arm. The only time I have ever encountered vibes was with the poly tranny mount. Put one in & got vibes. Took it back out & vibes gone. They are taller than the rubber mounts which causes the vibes.

FBOMB90

I'm new to this forum and I can already tell that the people I've talked to and the posts that I've read will continue to be useful. I'm a master tech in three different car brands and still struggle with some things from time to time. I don't care who you are and what you work on, no one knows everything! It's nice to know that I have somewhere to turn for GOOD info on my car. There is a lot of bad info out there and a lot of people who have no clue what they are talking about and just want to say something, whether it be useful or not. I appreciate everyone's input and it will all be considered.
Thanks again,
Pete

rarebmx

iTrader: (6)

I lowered ours and have the smae issue -

READ THIS - - https://www.thirdgen.org/forums/susp...nsion-how.html

nosajwols

iTrader: (1)

I am leaning towards pinion angle as well. Lowering the car can throw this off but I also noticed you have a new cross member (If I am reading that right). It is also possible that it also changed the height/angle of the transmission?

TTOP350

iTrader: (8)

Another thing to think about is your U joints.
If they have some miles, You may have changed the "working angle" of them just enuff and they could be a bit out of their normal worn in area.
Its fairly rare but can happen.

GTA1990

iTrader: (1)

not to ask you guinea pig, but great if you could post up if the adjustable torque arm solved your vibration problem.

I've got a similar problem after lowering my car - about 90mph+. Getting the car in shape this year for a summer trip down to the south of france and maybe the nurbergring on the way back up.

From what I've read I'll prob end up ordering one anyway but great to hear your feedback

SlickTrackGod

One greatly overlook problem to drivetrain vibrations is the engine harmonic balancer going bad. The inertia rings often slip and cause a load vibration.

When you lowered the car, you were also adding more soild suspension link bushings (ie- urethane mounts as opposed to rubber mounts. This driveline vibration can not be esily detected with just rubber mounts (ie-tranny mounts, LCA mounts, torquearm mounts) but once you change over to urethane or rodends the drivetrain vibration can and will be more pronounced.

Vibrations are either wheel imbalance, u-joints, bent axles, or bad harmonic balancer.

The TQarm angle will render a auditible vibration (the waa-waa's) but will not readily transmit a severve vibration just because the angle is off.

My guess is you have a bad harmonic balancer.

Dean

ps- I just wasted one on my truck and am replacing it as we speak. When I get hard on it (heavy load) uphill it will start to shake even the roll cage. It just developed and this truck has nothing changed recently suspension wise other than new high dollar tires that where very percisely balanced. Trust me it is amazing what a engine harmonic balancer will casue in regards to drivetrain vibration.

rarebmx

iTrader: (6)

My vibration started the first time I drove the car. To test your theory, at 60 miles per hour or faster I can put the car in neutral & I bet I feel vibration still. It is 100% for sure out of the rear of the car & I bet the original poster will say the same.
I was thinking of having all the wheels balanced again, then replace the tranny mount which I think is broken, then if the vibration continues adjustable panhard. A driveshaft being out of balance can also cause vibration.

SlickTrackGod

You bet you can? Or you can? Um k

Pretty simple to test this. Go uphill grade at 70 hard under throttle, and then go back downhill on grade at 70 in neutral. Don't bet, try it

SlickTrackGod

yes, this IS in fact a possibility. People will overlook new items since they are newish. However, as yous tated, they get a little waer pattern and then get changed they can easily make problems that are overlooked.

rarebmx

iTrader: (6)

Well I tested the speed at 60, pit car in neutral, same issue.vi happen to be driving at this very minute. My u-joints spindle based off rpm too, variation in gears don't Change anything either. It is overall mph. I think mine is from wheel balancing. I only went down maybe 1 3/4", springs & brushing only but I know for sure my tranny mount is bad, so I have a small list to do before I buy "extra" items to figure it out.