Cruising speed small vibration that is not tires: drive-shaft?

[PhoenixGTS]

I notice that my car has a very slight vibration when cruising at a steady 75-80 mph. It is not just at that speed but that is where I first noticed it. I recently changed wheels and tires and there was not change of this little vibration so I know it is not a wheel balance issue. I'm thinking it might be a slight drive-shaft out-of-balance, or perhaps even a half-shaft. Any other ideas? It is not horrible, you just notice a little flutter instead of completely smooth cruising and changing speed does not seem to change it much.

 

[dave6666]

You feel it through the seat? Pedals? Shifter? Steering wheel? Elbows on interior panels?

 

[ViperGTS]

My next thought would be "alignment" if not the wheels ...

 

[bluesrt]

My next thought would be "alignment" if not the wheels ...

alighnment will not cause a vibration

 

[crazyspeed]

Sounds like a "joint" to me. Time to buy a sirometer

 

[JonB]

rotor?
Lost part of stick-on wheel weights?
Inner wheel barrels CLEAN? No track marbles?
Hit any potholes hard?

I had the same thing.....jiggled-wiggled the Valentine One in my window. Annoyed me a lot.

"Road Force Balance" took it out completely, despite a 'normal' balance the month before.

 

[PhoenixGTS]

Exactly the same with two different sets of wheels and tires so I think that eliminates wheel balancing. I would describe it as coming from the rear of the car like it is a drive-shaft of rear end sourced issue. It is no where near severe enough to rattle anything. More of a very slight low speed warble.

 

[DVSGTS]

Might want to check the straps on the u-joints and make sure the bolts are tight. ?????

 

[dave6666]

More of a very slight low speed warble.

Can we just say then IT'S A VIPER?








Seriously though... Do you have poly mounts?

 

[PhoenixGTS]

Seriously though... Do you have poly mounts?

It is so small/low that you could chalk it up to being a Viper/radical car in general, but it coudl still be a problem or coming problem. I have stock engine and transmission mounts to it is not from stiff poly units transmitting the engine vibration.

 

[crazyspeed]

Sounds like a "joint" to me. Time to buy a sirometer

Before spending money and time chasing ghosts, you may want to buy a sirometer at a small engine repair shop and determine if it is a engine vibration...or a wheel/tire ( primary) or driveshaft/halfshaft/ujoint ( secondary harmonics) . Simply use the sirometer to verify frequency and then deterime from the chart according to vehicle speed and engine rpm vs sirometer reading ( frequency).
If any interest, I will try to look up and post more this weekend.

 

[crazyspeed]

Oh, I believe a sirometer costs about $16

 

[bluesrt]

Exactly the same with two different sets of wheels and tires so I think that eliminates wheel balancing. I would describe it as coming from the rear of the car like it is a drive-shaft of rear end sourced issue. It is no where near severe enough to rattle anything. More of a very slight low speed warble.

does it get worse when u slightly accelerate, low speed warble is usually a slipped belt in a tire or a bad c/v axle

 

[Fast Viper Dan]

I notice that my car has a very slight vibration when cruising at a steady 75-80 mph.

Simple, try 85-90?




I would still have a good, high speed wheel balance done.

 

[Bruce]

I had the same problem and thought it was a bent rim. As it turned out the tires had flat spots where the car had been sitting too long. Replaced the tires and everything works great.

 

[PhoenixGTS]

I had the same problem and thought it was a bent rim. As it turned out the tires had flat spots where the car had been sitting too long. Replaced the tires and everything works great.

Bad thing is I drive the car regularly this time of year and the tires are brand new. I'm thinking driveshaft.

 

[white out]

I have the same thing at 80mph.
My thoughts:
bad engine/trans mount
bad u-joint

Nick

 

[2000_Black_RT10]

alighnment will not cause a vibration

If caster is not set up correctly there can be a wobble or vibration, usually happens around 50 to 60 mph.

 

[GTS Bruce]

Agree with Dan. Just drive faster. GTS Bruce

 

[white out]

Are the wheels hub-centric?

Nick

 

[sdaddy]

I had a vibration problem in my GTS after switching wheels and installing drag radials. I would have sworn it was in the front as I could see the left front of the hood vibrating. It about drove me nuts. I had the front wheels rebalanced and that did not help. I had the right front and left front tires dismounted and switched and had them check the runout on the front wheels and that did not help. I bought new front tires and had them mounted so the LF wheel was now the RF and that did not help. I had the dealer check the suspension, hub, rotor and shock. He found nothing. I finally put the old front tires and wheels back on the car and still had the vibration. I put on the old back wheels and tires and it went away. Come to find out, one of the new MT ET Street drag radials I had bought had a heavy spot in the tire. When they tried to rebalace it the tire shop added 10 ounces of weight and could still not get it to balange to their satisfaction. I returned the tire to Summit Racing and they sent me a new one.

I had so real "seat of the pants" or steering wheel feeling with this vibration. It cam on at 65 and got progressively worse the faster I drove. Since the vibration was so visable in the left front hood, I would have sworn it was in the front.

This is the first time I had ever bought a new tire with enough of a heavy spot in it that it would not balance correctly, so I never gave that a thought. Lesson learned,

 

[DrumrBoy]

A driveshaft or u-joint issue would be present under load and invisible under zero load (or nearly invisible). If you're cruising at 70 and feel it, does it go away if you disengage the clutch or coast in neutral?

 

[PhoenixGTS]

A driveshaft or u-joint issue would be present under load and invisible under zero load (or nearly invisible). If you're cruising at 70 and feel it, does it go away if you disengage the clutch or coast in neutral?

Did some more seat-of-the-pants "testing" in light of DrumrBoy's comments. At 80 mph on smooth freeway, when I push the clutch in and coast the car is as smooth at butter. No vibration at all. But when I have the gas on and accelerate/decelerate above and below 80 mph by a few mph I have the small vibration. No power = no vibration. Power on = vibration. I would have thought that pointed toward motor mounts being the issue, but does anyone second DrumrBoy's idea that this indicates a driveshaft issue like I was originally thinking? I found a local shop that will replace my drivehsaft u-joints and rebalance it for $152 and wonder if I should pull the trigger (especially since I hear motor mounts are a PITA to replace). Sure wish I had a lift.

 

[RTTTTed]

Obviously a driveline issue. The driveshaft is easy to do a proper check pull the driveshaft and turn the u-joint cups. A sticky u-joint could cause a slight vibration, if it gets worse as the speed gets higher. Same thing if the driveshaft is dented or lost a weight (unbalanced). Same with rear axles (for the GTS) removed and bend all Ujoints to see if they have any tight spots. Have you checked the transmission fluid? Have you tried different gears to see if the vibration is engine/transmission/rpm related?

If the U-joints are old, it never hurts to remove them and put some grease into them (regular maintenance?). Might need to change transmission and Diff fluid?

Put the car on jackstands and in gear. Have someone turn the rear tire back and forth and see where the slack in the drivetrain is. Repeat with other wheel. If a U-joint has 'dead' needle bearings, you can usually see/feel the slack by a small amount of 'slack' or vibration between the cross and the bearing cups.

Ted

 

[white out]

Do the u-joints take grease or are they non-serviceable?

Nick

 

[white out]

Mine ended up being poorly balanced wheels.

Nick

 

[Jack B]

Do the u-joints take grease or are they non-serviceable?

Nick

If it was a pure out a of balance issue with the drive shaft it would still vibrate whether the throttle was open or not when you were at 80. That does not rule out a bad universal. Like RTTT said, get underneath it and lift the wheels off the ground, that is best done on a lift. You have six universal joints when you include the half-shafts. A bad bearing in a universal joint or in the rear end would be less apparent when you were off the throttle.

As was also stated, these wheels and tires can vibrate even after a balance. Assemblies this large should be road force balanced on a Hunter alignment system. The problem is many shops who have the road-force system do not know how to fully use all its features.

 

[PhoenixGTS]

As was also stated, these wheels and tires can vibrate even after a balance. Assemblies this large should be road force balanced on a Hunter alignment system. The problem is many shops who have the road-force system do not know how to fully use all its features.

Remember: 1) I have two different sets of wheels and tires and it is the same with both which tends to eliminate tire balancing issues; and 2) it is smooth as glass coasting at 80 mph which really eliminates tires balancing issues.

Does the yoke on the rear of the transmission slide in? Or is it bolted to the tranny static since the car has IRS? In other words, do I have the change the tranny fluid if I remove the drive shaft?

 

[Jack B]

Remember: 1) I have two different sets of wheels and tires and it is the same with both which tends to eliminate tire balancing issues; and 2) it is smooth as glass coasting at 80 mph which really eliminates tires balancing issues.

Does the yoke on the rear of the transmission slide in? Or is it bolted to the tranny static since the car has IRS? In other words, do I have the change the tranny fluid if I remove the drive shaft?

It slides into the trans. If you do not remove the trans cross member, the lift is level and it is not over filled it should not leak. I have a cap that plugs into the trans that i use for trans removal. My guess is most transmission shops have them.

 

['Trust']

I would mimic the problem again, note the exact RPM, then replicate that RPM in a lower gear and a lower speed. If it still does it then you can be pretty sure it is engine related and most likely normal (assuming your motor is fine, and they are pretty much bullet proof in stock form). If it doesn't replicate the problem it is more than likely drivetrain related, could be anything, clutch (try depressing the clutch at that speed to see what it does), drive shaft, half shafts, u-joints/straps etc. Try to narrow it down more. It could just be a worn trans mount (my money is on that or DS).