Daniel Parrott wrote:
>
> My 1980 Spit has been experiencing a little problem of late. Almost every
> time I take off from a standing start, I hear a "thunk" from the left rear
> tire area. At first, I thought it was a stone under the left wheel that
> shot out from under the tire under acceleration, hitting the wheel well. It
> does it just once, always from the left side. It has the tone of hard metal
> hitting hard metal, with little or no ringing present. I can sometimes feel
> the "thunk" as a vibration in the seat of my pants. When I accelerate from
> the stop light, I'm more likely to hear it when I start out "smartly" than
> from a smooth acceleration.
>
> The first thing that I thought was the left rear radius arm had lost it's
> grommet, but I jacked the car up and the radius arm, shock links, main leaf
> spring and u-joints on that side seem to be fit and tight, no leaks or worn
> rubber parts that I could see. I've replaced both half axels less than
> 5,000 miles ago.
>
> Before I take it to a professional, any ideas out there?
Dan,
You will undoubtedly get lots of people suggestion that you check the
U-Joints, especially the one on the side that is making the noise.
If you find the U-Joints to be in good shape you might find that you
have a loose or worn trunnion bolt or radius arm bolt that allows the
whole assembly to shift once but is held in place by the torque
afterwards.
The only way to detect this is to jack up the back end and with Jack
stands in place aggressively push, pull and otherwise move all the parts
that could cause this. In my case, it was the trunnion bolt that was
worn almost half way into. That caused the whole thing to shift when I
took off and back when I applied brakes. It didn't seem to cause any
handling problems but the nagging feeling that something was going to
give up on me caused me to take the whole thing apart and inspect the
pieces until I found what it was.
Cheers,
Joe
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