Vibration

[coupe351w]

The problem, a vibration. I get it above 40 mph and is bad at 90 to 100 mph or more. The vibration seems to be from the front seats back. The things I tried already, had all the tires rebalanced, still had it, had drive shaft rebalanced, still have it, tried different set of rear tires, still have it. What could it be?

Why I think it is not in the front, no shake at all in the steering wheel. I don't think it is in the transmission, the shifter doesn't shake.

Could it be in the rearend? Had it rebuilt about a year ago with new gears and all new stuff. The guy who did it knows what he is doing. I just don't know, and it is driving me nuts.

 

[marks73]

When you say rebalanced drive shaft, I'm assuming the U joints were checked and are correct. Typically a vibration at a higher speed but not felt at lower is U joints.

 

[coupe351w]

Sorry, new spicer u-joints put in when the driveshaft was rebalanced.


Also have a polyurethane trans mount, could this be the cause?

 

[MotoArts]

Possibly, but I wouldn't think so. I have poly trans./stock motor mounts in my '90, works fine.

Check motor mounts also.

Is it just speed dependent or RPM/load dependent ?

 

[coupe351w]

MotoArts, put on new ploy- motor mounts when I put the trans mount on.

 

[marks73]

Afraid it's time to pull punkin.

 

[coupe351w]

Dang, that rearend only has about 500 miles on it. What do you think ring and pinion not set right?

 

[marks73]

Tell you what you can try crazy as it sounds. Raise the rear and support it. Try the old screwdriver to the ear while someone rotates the back wheels and see if you hear anything. I'd check it at the rear of ring and pinion and as close to the wheels as you can get to safely. I use my stethescope from my old EMT days and it has helped on occasion. May be able to narrow it down before you do a lot of work.

 

[droptop73]

Are you running Magnum 500 wheels? if so make absolutely sure they balance the wheels off the lugs NOT off the center. It's hard to find a shop that knows how to do them right.

Check your driveshaft angles, both from the side and the top. If the angles are off it can cause vibrations. Check your pinion angle. Is your yoke into the transmission far enough? It should be about 1/2" from bottoming out at normal ride height.

Polyurethane can transfer more vibration to the chassis amplifying the feel.

I'm not sure on the rear gears, I've had them howl but not cause a vibration. Unless it's a bad bearing I would look elsewhere.

 

[c9zx]

Great ideas from Markmel and Droptop. Both suggestions are spot on. Chuck

 

[coupe351w]

Thanks guys, I just don't know. I just took my dad for a ride, he thinks it is the rearend. Like I said it comes on about 40-45 mph then gets more intense with speed and you really feel it in the seat of your pants. Thing is, it is not constant. What I mean is, it kind of acts like a broken belt in a tire. I thought that might be it, but like I said, I put a different set of tires on the back and it is still there.

 

[MotoArts]

I've had a bad rear in my company truck, an '08 Tundra, since we got it at 77K. Has 110K now. Buzzes hard enough to vibrate the toes at low speeds, but it occurs at any and all speeds. It just gets higher pitched the faster you go, but the vibration is minimal. This one's gonna grenade in spectacular fashion someday.

Several of our Chevy dually box trucks have howlers too.

They don't "vibrate", so to speak, just howl. You can vary the noise with the throttle.

Does your car have a "thump thump" kind of vibration at lower speeds (like a belt)?

Even thought you put new rears on, don't rule out fronts. Maybe try rotating them and see what happens.

 

[c9zx]

I haven't thrown a hail mary in awhile so, bent rim???? Chuck

 

[Tnfastbk]

I would relook at the simple things first. U joints, tire balancing, etc. I'm with Jeff on the rear end. I have heard them make some crazy noises with out vibration issues. If this a fresh project would check all the suspension/drive train bolts for tightness.

 

[coupe351w]

Finally got around to trying this, buddy who painted my car suggested it. I jacked it up, made sure it was safe on jack stands. Took back tires off, made sure rotors we're bolted to the axle good. Got car up to speed and put a flat edge up to the rotor, you know see if the rotor was bent or axle. Nothing they both were fine. While giving the car gas, I noticed a lot of vibration from the tranny and drive shaft tunnel. I'm still thinking the poly trans mount, just ordered new rubberized old style.

I'm going to give that a shot. Keep you posted.

 

[droptop73]

Check the pinion bearings too. You should not have any play there.

 

[coupe351w]

And the Verdict is in........... The Ploy Trans Mount.

Put the new old style in this morning, down the road I went. No Vibration.

Well it cost me over $130 plus my time too find that #%#@. Man am I glad that is gone and over with. Now on to a Nine inch rear end.

Thanks again guys for the help.

 

[c9zx]

I don't want to be a wet rag but, if the vibration was as bad as it sounded, changing to the old style rubber mount didn't make the vibration go away, it just damped it enough to not cause you to notice it. Hopefully I'm wrong. Chuck

 

[marks73]

+1 on C9zx Often times too many people deal withe syptom and not the core problem.