1979 L-82 Shudder Help!

[Elduderino]

[Michael H.]

Re: 1979 L-82 Shudder Help!

Just a guess but when radial tire belts shift or start to come apart, they create the exact problem that you describe. The problem shows up in the range of speeds that you mention. One thing that may be a clue is if the car seems to "wag" or "wiggle" side to side at slow speeds of about 3 to 5 MPH.

Tire belt issues can "come and go", just as it does on your car.

Balance isn't affected until wheel/tire speeds reach a certain RPM. It may not even show on the type of balancing equipment that spins the assembly.

If, by chance, you know of a set of wheels/tires that you can borrow for a test, it will prove the theory one way or the other.

Driveline vibrations typically become active in the 25 to 35 MPH range so I wouldn't expect to find problems in the drive or propeller shafts.

[Richard Price]

Re: 1979 L-82 Shudder Help!

Thanks for the help! YES it does wiggle side to side at low speed, like its going over gravel!!!

I will find some test tires, and just replace the existing ones if I have to.

Do you think this could be a bad differential?

And does it make since that the shudder goes away when I put the car in neutral?

[Mark Z.]

Re: 1979 L-82 Shudder Help!

Just a thought. Have you checked your fan clutch? I've had these symptoms with a bad fan clutch.

[John H.]

Re: 1979 L-82 Shudder Help!

The fact that accel/decel causes it to occur and it disappears during coast would lead me to check the diff nose bracket bushings where it attaches to the frame; when they deteriorate, it allows the diff nose to shift up and down, and the rear U-joint can rub the top of the tunnel.

[Richard Price]

Re: 1979 L-82 Shudder Help!

Thanks, I did suspect this and checked it. It is fairely new and in very good shape. I also instected the surrounding areas for evidence of shaft or u-joint scraping or touching and it all looks proper.

Thanks for the tip, please keep them coming.

Does anyone suspect the differential?

[Richard Price]

Re: 1979 L-82 Shudder Help!

SOLVED!

It was bad tires. I never would have guessed BECUASE... the shudder went away in neutral?

Thanks for all you help

[Michael H.]

Re: 1979 L-82 Shudder Help!

Thought so. When you accelerate or decelerate, it winds up the sidewall of the tire and causes it to run untrue if the belt or cord is damaged or broken. That's why you have zero vibration at "float", but vibration while accelerating/decelerating. Also why it comes and goes.

Not a very common problem but it does occur from time to time.

[Richard Price]

Re: 1979 L-82 Shudder Help!

Yes, very unusual problem, the tire shop ran the numbers on the Dunlops that came off the car and they were manufactored in 2005. They had less than 1000 miles on them so ... Factory defect?!? I think so...

Thanks again for the knowledge!