Transmission problem?

I've got a 99 Ford Taurus. Automatic transmission.

Recently, it has started `lurching' a bit when at idle in any of the
`Drive gears. With the brake on, it doesn't actually go anywhere, but
you can feel it trying to, and the engine slows down momentarily, then
comes back up to speed. The car idles at around 900 RPM, and slows to
700 RPM or so for a second or so while this happens.

In Park or Neutral, it doesn't do this (which isn't surprising.) And
when actually moving there's no problem either.

It's like there's a clutch in there that's periodically disengaging
for a second. It only does this sometimes, and I haven't found any
rhyme or reason to when it happens. But when it happens, it tends to
happen a few times per minute.

As it stands, it's not a big deal, but if it gets worse the car will
probably stall during these events. So it's something I'll probably
need to get fixed soon.

I'm certainly not equipped to work on transmissions myself (brakes are
about as deep as I get) but this sounds like something that actually
could be diagnosed from a description like this, and knowing more
about the problem (like what it probably is, what it'll probably cost)
is always good when talking to the mechanic ...

--
Doug McLaren,
Where are we going and why am i in this hand-basket?

On Sat, 18 Jun 2005 21:39:57 GMT, "Doug McLaren" >
wrote:

>I've got a 99 Ford Taurus. Automatic transmission.
>
>Recently, it has started `lurching' a bit when at idle in any of the
>`Drive gears. With the brake on, it doesn't actually go anywhere, but
>you can feel it trying to, and the engine slows down momentarily, then
>comes back up to speed. The car idles at around 900 RPM, and slows to
>700 RPM or so for a second or so while this happens.
>
>In Park or Neutral, it doesn't do this (which isn't surprising.) And
>when actually moving there's no problem either.
>
>It's like there's a clutch in there that's periodically disengaging
>for a second.

There is. You've got a locking torque convertor. Sounds like the
torque convertor clutch is not disengaging when you come to a stop.
It could be your brake sensor input to the trans isn't telling the
tranny that you're hitting the brake...

(As an aside, a locking torque convertor is used because in the higher
gears (like 3 and 4) the clutch plate holds the turbine side of the
convertor to the impeller side, creating a direct mechanical
linkage...non-locking convertors have a little slippage, which causes
gas mileage to suffer a bit. Normally, when the brakes are applied,
the convertor clutch disengages, and the torque convertor functions
like a non-locking type, until you get back up into the higher gears.



> It only does this sometimes, and I haven't found any
>rhyme or reason to when it happens. But when it happens, it tends to
>happen a few times per minute.
>
>As it stands, it's not a big deal, but if it gets worse the car will
>probably stall during these events. So it's something I'll probably
>need to get fixed soon.
>
>I'm certainly not equipped to work on transmissions myself (brakes are
>about as deep as I get) but this sounds like something that actually
>could be diagnosed from a description like this, and knowing more
>about the problem (like what it probably is, what it'll probably cost)
>is always good when talking to the mechanic ...

-LMB

Pull computer codes and see if there are any.



"Doug McLaren" > wrote in message
...
> I've got a 99 Ford Taurus. Automatic transmission.
>
> Recently, it has started `lurching' a bit when at idle in any of the
> `Drive gears. With the brake on, it doesn't actually go anywhere, but
> you can feel it trying to, and the engine slows down momentarily, then
> comes back up to speed. The car idles at around 900 RPM, and slows to
> 700 RPM or so for a second or so while this happens.
>
> In Park or Neutral, it doesn't do this (which isn't surprising.) And
> when actually moving there's no problem either.
>
> It's like there's a clutch in there that's periodically disengaging
> for a second. It only does this sometimes, and I haven't found any
> rhyme or reason to when it happens. But when it happens, it tends to
> happen a few times per minute.
>
> As it stands, it's not a big deal, but if it gets worse the car will
> probably stall during these events. So it's something I'll probably
> need to get fixed soon.
>
> I'm certainly not equipped to work on transmissions myself (brakes are
> about as deep as I get) but this sounds like something that actually
> could be diagnosed from a description like this, and knowing more
> about the problem (like what it probably is, what it'll probably cost)
> is always good when talking to the mechanic ...
>
> --
> Doug McLaren,
> Where are we going and why am i in this hand-basket?