So, today, I encountered a sudden vibration noise on my '85 GSL-SE. It used to be, going all the way up to 40mph, car was vibrating really bad.

I put the rear of the car up on jack stands, and put it in gear. I could get the same vibration while the wheels were spinning. I look under the car while it was idling in 1st gear and hear a faint "whorb whorb" noise near the transmission. Thinking it was the U-joints, I stopped the car and went inside the house to get some tools. About an hour later, I go outside to remove the plate that protects the driveshaft. I remove it and check both U-joints and found no slack, no play, or anything in both of them. I started the car up again and placed it into 1st gear, and even brought the wheels up to speed, and went through all gears. No vibration whatsoever.

I had no idea why it went away but I decided to give the car a test drive. Well, now I get a more noticeable, harsh vibration from standstill to 20 mph. After that, it's less noticeable, or even there, but I do get a fairly loud noise (hard to describe) that increases with speed.

I did a load test on the car, because I felt as tho the shudder was more apparent when putting a load onto the right rear wheel compared to the left rear wheel. I went in a circle in one direction, around 10-20mph, and it did feel that the right rear wheel was the cause of it.

I am not sure if it is my U-joints (altho no slack or play) or my wheel bearings. The U-joints are stock, AFAIK, and as far as the rear wheel bearings, possibly also stock as the rear end got replaced 2 years ago.

Any idea what it might be? Definitely need to watch my money big time and can't afford much. Plus, I found that U-joints for our cars are pretty much non-existent from auto parts stores, even Olympus (Import specialists).

 

Do you get the vibration when coasting with the clutch in and engine at idle?

Does applying slight brake pressure make a difference?

 

I have stuck the car into neutral, and still have the same ordeal. Braking, even to a complete stop, once I hit 20mph and below (in neutral even), it vibrates.

 

Bump for an update. I put the car back up on stands to inspect the wheel bearings. Thinking I had something rubbing my front right wheel, I inspected that, too. Nothing. Checked the rear wheels, nothing. I ended up unbolting the plate that covers the driveshaft and retested the wheels in motion (while off the ground).

Problem solved. When the passenger side of the metal plate was screwed back into place, it ended up being pressed up against the driveshaft. I confirmed this by pushing the plate into position and sure enough, it replicated the hassle. I took the car off stands and test drove it with only the driver side of the plate bolted in place. No noise, no vibration, nothing. Problem solved.

 

what protection plate are you talking about? the heat shield?

 

Whatever the plate is that is on the underbelly, that pretty much covers the driveshaft. It's found up above the exhaust piping, so yeah I guess you can call it the heat shield.