Drivetrain vibration

[J-440]

Around 45-55 I get a nice intermittent vibration. Checked the pinion, tranny, and engine angles and they seem to be correct. I have solid u-joints with no zerk fittings but I am running a front motor plate bolted to brackets and welded directly to the frame. Have not had the car over 55 as I am chasing a GV overdrive bug. This car is noisy and shakes and everything is brand new. Could the rotation of the crank be the source since I have no motor mounts?

[Peter Mc Mahon]

What rpm are you at when it happens? What if you get on the gas? Hold steady? Shift to neutral? Rev it to that rpm in park?

[J-440]

RPM's are around 2200 and it's a steady, intermittent drone. Have not done a test in neutral. Gonna try that today. Thanks

[andrewb70]

It is entirely possible that engine vibrations are going to the frame and causing this.

Andrew

[QA1_Bill]

If the vibration is speed dependent, it is likely something in your driveline or wheel/tire package. If it's RPM dependent, you may be able to feel the vibration when the car is sitting still by just raising the RPM to the point where you've felt the vibration.

Driveline vibrations can be difficult to diagnose, but the first place to start would be to make sure your driveshaft is straight and properly balanced. We actually use different width E-Clips to retain the u-joints which will move the joint side-to side slightly when balancing ours and it does make a big difference. If you installed the joints yourself and haven't had the driveshaft balanced afterwards, that very well may be the source of your vibration.

[J-440]

Would I be able to see the driveshaft vibrate if I tested the car up on jackstands? Or would this be an internal thing and I wouldn't be able to see it?

[QA1_Bill]

No, I highly doubt that you'd be able to see it vibrate if up on jackstands. Your best bet would be to take the driveshaft (complete with U-Joints and slip yoke) to local shop who does driveshaft work and have them check the balance. Before you do that, make sure your pinion angle is correct. It should match the angle of the slip yoke. Tremec has an app for smart phones that can help show you your driveline angles.

[Peter Mc Mahon]

So does it do it at 2200 rpm in park? 3000 in park?
Next, I would drive at the 2200 rpm zone and then shift to neutral and get off the gas, what happens?

[J-440]

Appreciate the help. Gonna play with it this weekend.

[minendrews68]

Does the car have this "drone/vibration" sitting still with the motor running?

[J-440]

No, only at speed.

[Mr Nick]

RPM's are around 2200 and it's a steady, intermittent drone. Have not done a test in neutral. Gonna try that today. Thanks

,

What do you mean by intermittent? Does it come and go consistently as you're going down the road at 2,200 rpm?

I'm dealing with something like that right now, according to the Tremec app, the U-joint angle at the trans was off, but the pinion angle was good. I installed a new trans mount with a space, which lifted the trans about 0.25", that change made an improvement but the pulsing vibration is still there. I'm going to re-check my angles and hopefully one more spacer to lift the tail of the trans a bit more will fix it.

[dhutton]

What kind of trans mount do you have? I would expect some vibration with an engine plate and no motor mounts.

Don

[J-440]

Yes a pulsing would be another word. I revved it to 2500 in neutral and there is no vibration so now I'm assuming it is the driveshaft. The tranny is a stock mount. Downloaded the TREMEC app and am going to do some diagnosing.

[icemanrd19]

If your cruising say 65 mph and bairly touch the gas does it Humm and vibrate then? Bairly touching as in almost resting your foot on the gas

[J-440]

Can't get it over 50 and don't want to push it. It's a very loud pulsing noise and when I let off the gas the noise stops at 40mph. So only in between 40 and 50 mph.

[Peter Mc Mahon]

So what about 2200 rpm in first gear going much slower?

[Mr Nick]

Can't get it over 50 and don't want to push it. It's a very loud pulsing noise and when I let off the gas the noise stops at 40mph. So only in between 40 and 50 mph.

There is a noise along with the vibration?

[dobie6982]

I just had driveline vibrations once I got up to about 60-70. I had the tires balanced and it didn't cure it. I checked my pinion angle and it was one up. I put in some 2 degree shims and removed the isolation pads between the leafs and axle. Almost all the vibration is gone and the car seems to handle better. My pinion is now 3 down. If that did not work for me my next move was having the driveshaft inspected. Do you feel the vibration in the seat of your pants or the steering wheel?

[J-440]

The vibration/pulsing is right behind/below me. I've got a buddy with a lift and a digital angle finder. Shouldn't be too hard now. Going by the angles in Kyle Tucker's pro-touring bible, the engine/tranny should be -3* and the pinion -1.5* for my suspension setup.