Having a hard time determing vibration cause

[fastsvo]

I am experiencing a good solid vibration at freeway speeds (more like 75-80mph) and I almost want to call it a shudder because I can feel it in the steering and under neath my seat.

The car is a '91 with only 58k on the clock.

I searched around the forums and took down these notes:

a) No vibration while car is in neutral and speeds >= 80 ---> engine/trans mounts/ harmonic dampener

b) VIBRATION while is in neutral and speeds >=80 ---> driveshaft, gears, rims

c) Rear bearings in the carrier of the differential

d) Tail shaft bushing in T-5 Trans


Now, I was taking a look at my driveshaft and noticed while the pinion flange has a faint yellow mark aligned with the purple dot on the DS, there is also some white paint on the rear u-joint.

Does it look like the driveshaft is installed correctly?

As for my differential, I do have an Auburn unit and it makes some minor noises when backing out of a parking spot for example...isn't this normal for an Auburn?

Thanks in advance!

-Eric

http://i69.photobucket.com/albums/i45/fastsvo/IMG_1544-1.jpg
http://i69.photobucket.com/albums/i45/fastsvo/IMG_1545.jpg

[Krwy]

Usually those vibrations are from the DS. Loosen it up and rotate it then see how it feels.

[fastsvo]

I reclocked the DS and the drive line vibration went away, but the car is still plagued with heavy vibration from the front end @ highway speeds. I feel a lot of vibration coming through the steering column and dash. A long time ago I had the wheels balanced, but the car has not been driven much (800 miles).

Could it be a motor mount?

The front end has new struts, spring isolators, MM alloy rack bushings, MM steering shaft, but still has the original tie rods and ball joints.

Thanks,
Eric

[vtecftw]

a while ago, my car had a lot of vibration and it turned out to be the motor mounts. make sure to get a good view of them. i _thought_ mine looked fine from the bottom, but after i pulled them off i found out the rubber was falling apart. could always use it as an excuse to get prothane or energy mounts, if you don't have them already.

[fastsvo]

I am little hesitant on the poly mounts due to the vibrations. Do you have those aftermarket mounts as well?

-Eric

[91gtstang]

i had that before and it was my tie rod bushings

[fastsvo]

Tie Rod bushings? Are you referring to the tie rod end links?

[Martini]

vibration at high speeds usually indicates steering/suspension/alignment problems. i think before you start changing motor mounts inspect your tie rods for any unsuall play. they should rotate but shouldn't have any play either in or out on the joint it self. it could be that simple.

[91gtstang]

Tie Rod bushings? Are you referring to the tie rod end links?
all i know is i had a chrysler that was doing the same thing and the mechanic said the bushing was broke and he replaced it and it didnt shake no more

[ka0tyk]

I am little hesitant on the poly mounts due to the vibrations. Do you have those aftermarket mounts as well?

-Eric

dont be a pvssy. i have the solid MM mounts in my car and its not even bad. prolly the same as poly.

and if you're experiencing shaking of the steering wheel its time for new tie rods. inners are like $20 and outers are like $15. aaand of course anytime u mess with those its time for alignment. weee.

[Blind]

Swap the wheels/tires for a spare set, I'm betting it's the tires are out of round or some kind of imbalance.

my blazer had a wicked shake at highway speeds felt through the seat and steering wheel when I bought it, rotating the tires moving the fronts to the rear solved 90% of it, buying new tires cured it. The tires also killed a balljoint and idler/pitman arm in the steering though, but the p/o had been driving it that way for close to a year before I bought it. When I replaced the tires the vibration was gone but the steering felt loose and had a large dead spot when on center.

[fastsvo]

Swap the wheels/tires for a spare set, I'm betting it's the tires are out of round or some kind of imbalance.



hmmm...I don't have an extra set of 4 lug wheels/tires....if the car was only a 5 lug!

-Eric

[Martini]

what you could do is jack up the car.

put your hands on the tire at 3 and 9, and lighly press back and forth, if you're getting movement then it's your tie rods.

put your hands on the tire at 12-6, and lightly press back and forth, if you're getting any movement then it's your wheel bearing.

---------- Post added 07-31-2009 at 02:33 PM ----------

oh yeah forgot to add, you have any tire wear patterns?

[ka0tyk]

do you have gears? just curious as to why the paperweight is still on the rear end...

[fastsvo]

do you have gears? just curious as to why the paperweight is still on the rear end...

???

[vtecftw]

i think he means that heavy dog bone damper on the rear end. i just took mine off and didn't notice a difference. although i'm running dumped spintechs so it's hard to tell =/

[ka0tyk]

???

the 10 pound weight bolted to the rear end was referred to as a "vibration dampener" by the factory. otherwise known as "extra weight" or a "door keeper opener" :afro:

[Martini]

the 10 pound weight bolted to the rear end was referred to as a "vibration dampener" by the factory. otherwise known as "extra weight" or a "door keeper opener" :afro:

is that the official term?