You could be describing a bad engine or tranny mount easily.
I check for that by opening the hood and having someone start it, hold the brake down and put it in drive then give it some gas. I then do the same in reverse.
If there is a bad mount there, one of those tests will show it.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT'ssnipped-for-privacy@m>
Hi:
>
> I have a 1989 Cutlass Ciera with the 3.3 liter engine and automatic
> tranie...suppose all 3.3's had auto. The car has 75 k miles on it and
> runs great. No problems other than the following:
>
> Recently the car developed a strange and somewhat disturbng noise.
> It's a knocking, scraping noise that can be felt slightly in the floor
> board BUT!!!!!!! it only occurs under certain conditions.
>
> When the car accellerates around a left hand turn AND when allowed to
> straighten out by itself but still under accelleration the noise is
> quite audible. Again it sounds like a thumpng noise. Initially I
> thought is was the exhaust hitting the bottom of the car but this is > not the case.
>
> The noise occasionally also occurs when going over bumps in the road. >
> Also under heavy breaking just before the car comes to a stop, but
> this my not be related.
>
> I've crawled around underneath the car many times but can find no
> evidence of what may be making this noise. I have NO reason so far to
> think it's a CV joint problem. There is no evidence of a problem with
> any motor mount. Breaks themselves are fine.
>
> The noise is NOT gear specific, it occurs in both first and second
> gear when accelerating around a left hand turn. Not sure about higher > gears.
>
> It's not the easiest thing to demonstrate either. Yesterday I went to
> an empty parking lot and kept n the gas while going around to the left
> until the tires squeeled but no noise was heard!?!?!?!?
>
> It seems that there also have to be slight road irregularites, i.e. at
> least some small bumps in the road. In fact now that I think of it, it
> is actually more dominant when going over slightly bumpy roads.
>
> I did replace the front struts recently but the noise did not develop
> until quite some time after this. Just be safe I removed the left hand
> strut assembly a week ago but no evidence on any problem. Also I rock
> the car up and down all day long while stationary and not hear the > noise.
>
> I'm really stumped but concerned because this sounds like it may be
> something serious or could be at some time in the future.
>
> There is no evidence of wheel bearing problems but should I consider
> this? Is it some type of bezzare tranie problem?
>
> Any help or pointers would be GREATLY appreciated.
>
> If possible send or copy any response to:
>
> snipped-for-privacy@mindspring.com.
>
> TIA
>
> Marc