Loud thud under gas pedal

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Loud thud under gas pedal

Postby jwhitmore » Fri Sep 12, 2014 7:06 pm

I have a 1980 fiat spider. I was driving along at 80 miles per hour on the freeway when I felt and heard a loud thunk under the gas pedal. It felt as though a big rock hit under my car. I looked behind me in the road but didn't see anything and I certainly didn't see any debris in the road ahead of me because I usually try to miss those things. There was no problem with any of my gauges. I stopped at the next exit, opened the hood, looked under the car, but could not find anything wrong with the under carriage or inside the engine. Everything looked fine.

So, assuming it was just road debris, I got back into the fiat and started driving again. 15 minutes later I felt the exact same thing again. I wasn't slowing or speeding up or turning or doing anything out of the ordinary, just driving steady state at freeway speeds. Again, absolutely no issue with my guages at all.

I continued to drive home with no issues. I'll be taking the car to the mechanic for an oil change next week so I'll have them check it out but I like to have some idea of what something is before I turn my car over to someone else.

Anybody have any ideas?
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Re: Loud thud under gas pedal

Postby jwhitmore » Wed Sep 17, 2014 3:43 pm

This was diagnosed as a bad Universal joint on the drive line. Thoughts?
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Re: Loud thud under gas pedal

Postby daled » Thu Sep 18, 2014 1:06 pm

diagnosis is plausible..
rubber u-joint just aft of transmission may be coming apart.
my Alfa made similar noise about 2 days before it stopped pushing the car..

PS be glad you don't have to fix this on an Alfa, its a PITA compared to a 124...
71' 850 with (1.8L)
58? abarth 750
81' 124 (3.0L)
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