Driveline vibration

[mdeal619]

1985 c20 constant vibration especially in the cab. New tire, ujoints, center bearing.
350 turbo 400 and 4.10 9 1/2” differential. Any help or ideas how to narrow this down by myself first. The vibration starts right after take off and only gets worse on the highway.
Mike

 

[Originalthor]

Check to see if you possibly lost a weight on your driveshaft. Rare but I had it happen to me. But usually don't start feeling it until getting up in speed.

 

[fast 99]

What speed does it start? Usually a low speed vibration is driveline or engine related. Wheel speed vibrations are usually at higher speeds unless it has a broken tire belt or wheel falling off.


edit, would help to know what speed and if any work was done preceding. You say right after take off. That to me indicates less than 10 mph.

 

[Rickf]

Get the rear wheels off the ground and run it, if the vibration is still there, remove the wheels & run it. If the shakes go away, it's the tires or wheels. Remove the driveshaft, if the vibration goes away there's your problem. Start from the rear disconnecting components to isolate the vibration.

 

[PeteJr]

Pinion angle ?

 

[peats]

My '72 k5 came with 3 different size bolt/nut combinations on the torque converter. Easy to check

 

[SirRobyn0]

If you have the semi-float axle you might have a belt axle. I'm actually running around on a slightly bent LR axle, feels surprisingly similar to a U-joint, but in my case more mild.

All you have to do is jack up the rear end and run it. Carefully look at the lip of the drum for movement. Then of course you can pull it out and check it with a straight edge.

I've also heard of the bearing or sleeve for the output on the transmission getting worn causing vibration.

 

[wlwarnke]

Obviously the vibration is vehicle speed related. What frequency is it? Driveshaft speed? Wheel speed? (Driveshaft is 3.73 times faster than axle/wheel for example).

For reference, drive shaft is usually a faster hum while wheel is a slower shake.

Sort of like a lifter tapping is 1/2 engine rpm.

 

[R Carnella]

Definitely put it on stands and check the axles like mentioned if it's a Semi float. My driver's side axle was bent.

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[SirRobyn0]

Definitely put it on stands and check the axles like mentioned if it's a Semi float. My driver's side axle was bent.

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I'm still running around on my slightly bent LR, hey do you happen to remember what brand of axle your replacement is?

 

[R Carnella]

Yeah i bought it from Summitt racing.

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[SirRobyn0]

@R Carnella Thanks for that info. Those axles are a better price than I can get locally.