# Drivetrain vibration



## deanhickey (Apr 6, 2015)

I need a some suggestion to diagnose a vibration in my drivetrain. On the road at 55mph the entire car starts to vibrate. With the car in neutral at 5k rpm no vibration. with the wheels in the air vibration comes in early and seems stronger. Replaced u-joints last summer and will check the driveshaft for runout with a dial indicator tomorrow. Did not notice the vibration last year. the diff is running open but is a safety track unit with the clutches gone. the tires are Goodyear Wing foot (last made in the 80's). will also inspect transmission mounts. Is there anything I a missing? any suggestions will be appreciated .
Dean


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## O52 (Jan 27, 2019)

40 year old tires are a disaster waiting to happen. Put some modern rubber on there and then recheck. 
Driveline may be out of phase too. Try removing and turning the driveshaft 180* and recheck. 
Driveline pinon angle may need adjusting. 





Drive-line Geometry 101 - Classic Truck Shop


Classic Truck Shop - Featuring Classic Chevrolet Trucks, Dodge Trucks, Ford Trucks, Project Trucks, and Truck Articles.




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Spicer Driveline Operating Angle Calculator


Measure the angles of each component in your drivetrain, then use the Spicer Driveline Operating Angle Calculator to find the operating angle of each u-joint in your drivetrain.




spicerparts.com




Most smart phones with a measurement/angle app can be used to measure pinon angle


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## Lemans guy (Oct 14, 2014)

Wheel balance is the first thing I would be certain of. Out of balance wheels and tires will vibrate at a certain speed. Wheels weights fall off, even if you think you did it recently. The tires wear and get out of balance as well.

Driveshafts also are balanced there are small weights on them. Rarely need anything, but after 50 plus years things get out of whack. Pinion alignment also has to be correct, the shaft to the Pumpkin and the shaft to the trans must be in spec. Too much angle will cause vibration problems.


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## Lemans guy (Oct 14, 2014)

Tremec has an app to measure driveshaft pinion angle with your phone. It is free, just download it.


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## deanhickey (Apr 6, 2015)

I think I have eliminated the tires as a cause. removed them and secured the drums with lugs and still have the vibration so the next step will check the shaft and the U-joints. thanks for the steer on the tarmac app.


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## O52 (Jan 27, 2019)

From the 70 Assembly manual


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## 67ventwindow (Mar 3, 2020)

I have 50 year old tires on a tractor. They are like stone. I cant image being at speed and hitting a pothole. They would desinigrate before one revolution.


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## armyadarkness (Dec 7, 2020)

Are you using the original rear wheel bearings? My car had 70k original miles and they were in pieces.


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## deanhickey (Apr 6, 2015)

Found the issue. it was the rear u-joint. Now to start saving for new rubber. Where are the best deals on tires?


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## armyadarkness (Dec 7, 2020)

Im questioning the integrity of my rear ujoint and its new. You said that yours was new too. Where is it from?


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## Lemans guy (Oct 14, 2014)

Summit will give you a great price on Cooper cobra radial GT, with white letters....


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## O52 (Jan 27, 2019)

Discount/America's Tire stores.
Costco for BF Goodrich


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## nick rice (Nov 10, 2014)

Thinking driveshaft but still can't see you driving around on such old rubber.


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## deanhickey (Apr 6, 2015)

nick rice said:


> Thinking driveshaft but still can't see you driving around on such old rubber.


new rubber ordered.


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