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Discussion in 'Troubleshooting & Diagnosis' started by Glava, Nov 15, 2021.
Could also be a bad belt in the tire.
Wheels and tires are a huge source of vibration. If you know you have a bent one, get it fixed or get rid of it. The worst part is that you can get a bent wheel to balance perfectly on a wheel balancer, but it still shakes the car on the road.
I love my factory steel Z28 trims, but at least one of them had enough of a bend after 40 years that I could not get rid of (another) shake. So, on with a new set of aluminum wheels and Cooper tires, and it is smooth again. I have solid body bushings, poly engine/trans mounts and poly rear spring eye bushings along with heavy springs, so I feel every vibration that the car and the road can come up with. Straight wheels are a necessity.
These gremlins can be hard to track down. I'd get the drive shaft balanced and have them put 2 new U-joints in it. Its a process of elimination. Seeing its a 4 speed manual, a bad drive shaft or transmission output shaft would be felt in the shifter and you mentioned seat of the pants. It could be the rear end pinion bearing, axle bearings, or even carrier bearings. Other things to check are the rear brake drums and or front rotors , its a long shot but you end up with new brakes all around which isnt a bad thing. I dont believe its the engine or it would rpm related. Could it be the second set of tires were bad? I chased a vibration problem for years. I found a bad U-joint ( didnt fix the problem) and finally replaced the quite new BFG radial T/A's because of age. The tire(s) was the problem all along. Had them balanced twice once the vibration started and they balanced out fine. My vibration was around 65 mph and up. Do you know anyone that you could swap out all 4 tires/wheels with for an afternoon?
Mine turned out to be the tires as well. I stumbled on what the issue was one day when i coasted down a hill with the engine off and the trans in neutral. The car had a slight hop to it.
Rotating front to back usually will ID a tire problem. The vibration will change or go away. .
Rotating front to back is a great idea. But do one side at a time. Rotate just 2 tires, ( right side first, front to back) if nothing changes, do the other side. If you could find just one spare tire, you could try that. You car probably has limited slip rear end so the spare has to be very close in size to the other tires. Most tires are balanced at a lower speed, show it usually doesnt show up at a tire shop.
Yes, one rim was out of round or bent -I had it replaced over 30 years ago
My crazy problem is that the tires have been replaced once and rotated at least 10 times over the years and the vibration has always been the same. Both sets of tires were re-balanced many times.
The original tires were on it for 30+ years, with the vibration -only an issue at about 70mph. So when I replaced the tires may 5 years ago, I thought that would get rid of it, but it didn't and I can't imagine that the old tires and new tires had a bad belt, but thanks!
We had a dusting of snow last night, so I'm waiting for dry roads to do some road test verification:
1) I'm going to confirm the vibration at 70mph, then verify if there is anything at 60mph and 80mph -as others have said, vibration problems show up differently at speed depending on the likely source, so maybe that will eliminate something.
2) Then I'm going to put it on jack stands and spin the drive shaft and see if it is straight at the rear, middle and front -also look at and check out the U joints. But, depending on confirmation of the vibration pattern at different speeds, I will probably pull the driveshaft and have it checked for balance.
3) Since the same vibration has occurred with two sets of tires and one replaced rim, I'm going to forget the tires for now, but I'm going to rotate them and inspect the rims for any obvious out of round or dents.