Had this lady with a Dodge Dakota pickup that had a slight vibration.
She told me she thought it was the tires; she had them put on a couple of months ago.
She took the truck back and had the tires balanced again, but it didn't seem to help.
I drove it down the road and noticed it did feel like rough pavement, sorta like little 'ribs' across the road.
I noticed when I gave it more fuel or let off of the accelerator, it would quit vibratingit smoothed out and ran like a Dodge ortta.
I put it on the lift and raised it to where I could turn the tires. No noise. I shook each one back and forth. No looseness in the bearings or tie rods.
I thought it could possibly be a bearing in the differential.
I turned the rear wheels but didn't hear any bearing noise, so I started checking the universal joints in the drive shaft.
No slack that I could feel or see.
I took a large screwdriver and pried against the cross on the rear u-joint--Ah ha! The joint had just a little bit of slack in it.
When I removed it from the drive shaft I removed the cups.
Two of the cups were almost completely void of grease and the shaft on the cross had 'ridges' where the needle bearings had been riding on it...
without grease, it had worn groves in the shaft, causing the slackness
causing the vibration.
When a universal joint gets a little slack, and you have it balanced at, say 55mph, then it will vibrate.
If you let off the accelerator, or push the accelerator, you put the drive line in a bind. When it gets in a bind, it quits vibrating.
After installing a new universal joint and replacing the driveshaft, there was 'no' vibration when I test drove it.
She was so proud of meshe cooked my favorite meal, pork-chops, and invited our children over for supper.
Tommy Sessions has been in auto repair since 1970. He publishes Auto Repair Answers Newsletter so you can learn how to keep your vehicle looking new, running safely and efficiently, while you save money and time...also, learn how to avoid shop rip offs. Don't be at the mercy of the dealerships and auto repair shops...they will have more respect for you.
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