Weights on outside of wheels

[Duke W.]

Re: Weights on outside of wheels

I doubt if alignment is the issue. Did this problem start after the new tires were installed? What's the make, model and size of the tires?

Can you estimate the frequency of the vibration, and do you have a sense where it is coming from? Is the vibration frequency constant or does it vary with speed. At what speed does it start and stop.

You said it only occurs under heavy acceleration in first gear, and I assume it's a manual transmission. Describe what happens as if we are watching a movie - every possible detail.

The better you can characterize the problem the better the diaganosis can be.

Duke

[Joe L.]

Re: Weights on outside of wheels

Hi Duke and Paul,
Thank you for your replies. The U-joints, engine mounts, front end components, and knock-off spinners have all been visually & physically inspected and were found to be in good condition. As you said Paul, something may be on its last leg and just isn't giving us a clue yet. The only things that were suggested in the old thread that I haven't tried yet - because it required actually doing it and not just inspecting it - was tire balancing and reducing the rear wheel camber. When I saw this thread on wheel balancing, it reminded me about the vibration. I recently installed new front shocks (they were shot) and rear leaf spring cushions (they were only 2 years old, but looked dry-rotted) and, although the heavy acceleration vibration isn't completely gone, it isn't as severe as it was before. I also don't remember having that vibration a couple of years ago before I rebuilt the rear suspension (trailing arms, strut rods, mounts, shocks, etc.). It sounds like wheel balancing wouldn't be associated with a vibration that only occurs under heavy acceleration, so I am beginning to think that it could be from too much rear camber. In the older thread, someone posted a bulletin from GM/Chevrolet which suggested to reduce the rear camber to eliminate this type of vibration. If I remember correctly, it said to bring it down close to "0". My front & rear camber, before replacing the front shocks & rear leaf spring cushions, was within spec from what I have read: left rear = -0.32* and right rear = -0.43* / left front = +0.48* and right front = +0.48*. Could the alignment be the issue?

Thanks again,
Roger (50141)

Roger-----


If you're talking about inspecting the u-joints while they are installed on the car, it won't tell you anything unless they're so bad they're at the point of imminent catastrophic failure.

[Roger P.]

Re: Weights on outside of wheels

Duke and Joe,
The U-joints were inspected off the car when the rear suspension was rebuilt just over 2 years ago and they appeared fine at the time. Of course, I realize that isn't a guarantee that they are fine. The tires are approaching 4 years old with about 4,000 miles on them. They are Yokahama Aegis whitewall radials; 215-70 R15 mounted on knock-off with spinners. They provide a very nice ride at all speeds with good handling and no vibrations. I didn't notice the problem before or shortly after changing the tires, however they were replaced a right after I purchased the car. The issue isn't a major problem and that is why I haven't thrown money at finding a solution, but I certainly would like to know what it is so I can take care of it. What basically happens is as follows... When entering the highway, if I decide to lay into it pretty hard (which I don't do very often), I feel the front end of the car vibrate with moderate intensity. I don't feel the vibration coming from behind me; it appears to be coming from the front end. I feel it in the steering wheel and perhaps a little in my seat. Speed isn't the issue, but rather the torque when starting out from a slow speed. If I'm cruising on the highway and nail it, I don't have the vibration issue; only from standing still or moving slowly and then "hitting it" hard. Once I feel the vibration, it will stop if I back off the gas a little. The end of the movie is me cruising down the highway with a smile on my face !! I know that my smile could be ear-to-ear if I could figure this thing out . When I look at the front end components, the rubber bushings look "tired" to me (old and showing some small cracks). However, a few mechanics have all told me that everything was tight and wasn't worn to the point of needing replacement. I attached a few photos from my pre-purchase inspection a few years ago. Anyone coming down to South Florida for a vacation this year??

'65Vette-Chasis-04.jpgPicture 043.jpgPicture 044.jpg

[Michael W.]

Re: Weights on outside of wheels

Engine or transmission mount.

[Duke W.]

Re: Weights on outside of wheels

Do you have the original motor mounts - the type that dont have the elbow to limit movement if the mount breaks? If so, they may be broken, but it may not be obvious from visual inspection. Blipping the throttle hard while looking at them may show excess engine movement. If nothing is obvious, I recommend you remove them for careful inspection, and be prepared to buy new ones.

Duke

[Roger P.]

Re: Weights on outside of wheels

Michael and Duke,
It has been raining non-stop for a few days here in South Florida, so I haven't had a chance to play with my car for a while. I hope that Friday will be a day that I can get away from my work a little early and get behind the wheel again. A mechanic friend visually checked my motor mounts for me several months ago as I suspected they were the culprit (the tranny mount & differential snubber were replaced about 2 years ago). I will take a closer look on Friday or over the weekend and let you know what I discover. It wouldn't surprise me if the mounts were the problem as they were the first thing that I thought of when I initially became aware of the vibration. In addition to the movement of the engine when I "blip" the throttle, what should I be looking for when I visually inspect each motor mount?

Thank you,
Roger (50141)

[Joe L.]

Re: Weights on outside of wheels

Michael and Duke,
It has been raining non-stop for a few days here in South Florida, so I haven't had a chance to play with my car for a while. I hope that Friday will be a day that I can get away from my work a little early and get behind the wheel again. A mechanic friend visually checked my motor mounts for me several months ago as I suspected they were the culprit (the tranny mount & differential snubber were replaced about 2 years ago). I will take a closer look on Friday or over the weekend and let you know what I discover. It wouldn't surprise me if the mounts were the problem as they were the first thing that I thought of when I initially became aware of the vibration. In addition to the movement of the engine when I "blip" the throttle, what should I be looking for when I visually inspect each motor mount?

Thank you,
Roger (50141)

Roger------


The main thing is separation between the steel and rubber components of the mounts. However, this can be hard to detect with the mounts installed on the car.

[Duke W.]

Re: Weights on outside of wheels

...which is why the best course is to remove the mounts for inspection off the car.

Duke

[Kurt G.]

Re: Weights on outside of wheels

A trick you can use even on a flight judged car for a good dynamic balance is to use the clamp on weights on the back side of the wheel and the tape weights under the trim rings.