Short Vibration on 2001 Windstar whenever A/C compressor s..

I have a 2001 Ford Windstar with 102,000 miles. Sometime over the past
few months it started to get a periodic vibration. It lasts about 1
second (maybe a bit less), and feels like you just rolled over a
series of 2" pipes. It's most noticeable on smooth highway driving,
but I'm pretty sure I've felt it on surface streets also. They are
just so bumpy around here that often it is hard to tell. Eventually I
realized it only happens when the A/C is on, and is more frequent when
it is hotter outside. Generally it happens every 30 seconds to 3
minutes, and it usually happens within a couple of seconds of first
turning on the A/C. For this reason I'm assuming it happens whenever
the compressor starts up.

The Ford dealer is guessing that it is the torque converter, but
that's only a guess. It will take a $2200 repair to find out, so for
now I don't plan on doing anything unless the torque converter fails.
I asked what the tie-in with the A/C is, and the best they could do
was speculate that the added engine strain somehow triggered it. It
sounds pretty fishy to me, especially since the transmission is rock
solid (by both my experience and their testing). A transmission flush
didn't help at all.

Any other ideas as to what the problem might be?

jmail.plummer.RemoveThis@sun.com wrote:
> I have a 2001 Ford Windstar with 102,000 miles. Sometime over the past
> few months it started to get a periodic vibration. It lasts about 1
> second (maybe a bit less), and feels like you just rolled over a
> series of 2" pipes. It's most noticeable on smooth highway driving,
> but I'm pretty sure I've felt it on surface streets also. They are
> just so bumpy around here that often it is hard to tell. Eventually I
> realized it only happens when the A/C is on, and is more frequent when
> it is hotter outside. Generally it happens every 30 seconds to 3
> minutes, and it usually happens within a couple of seconds of first
> turning on the A/C. For this reason I'm assuming it happens whenever
> the compressor starts up.
>
> The Ford dealer is guessing that it is the torque converter, but
> that's only a guess. It will take a $2200 repair to find out, so for
> now I don't plan on doing anything unless the torque converter fails.
> I asked what the tie-in with the A/C is, and the best they could do
> was speculate that the added engine strain somehow triggered it. It
> sounds pretty fishy to me, especially since the transmission is rock
> solid (by both my experience and their testing). A transmission flush
> didn't help at all.
>
> Any other ideas as to what the problem might be?

A mechanic who doesn't know what he is talking about.