Hello folks. I have posted this in "General Tech" and "Transmission" discussions as well.
We have a 2003 Sable with just over 155,000 miles. I have recently noticed, it lunges forward a bit when I start it. I only notice this when the engine & trans are cold. Is this normal for these vehicles?

 

Sounds like it could be. My 2000 with the Duratec engine would do the same thing. More prodominately when the temp was 45° or colder.

 

Why would that be normal? The transmission should be in park or neutral when you start it. It should not lurch forward until you put it into drive after it warms up. The rpms should drop when you do this.

 

It's not a lurch, it's a slow movement that is about the same as one would get when you place a vehicle in park and remove your foot from the brake and get that momentary movement from the transmission. Basically all of the slack in the drive system is being taken up when the engine starts and turns the torque converter which causes the motion. My 2000 Taurus was just sold with about 290,000 miles on it and it has done it since new and all of its life with no issues.

 

I under stand that when your putting the car in drive or reverse . Thank you .

 

It is true, it is not a lurch or lunge forward per se`, it is simply just enough motion in the forward direction to be felt. I wouldn't say it even amounts to an inch of movement. I was just curious about it cause I have never experienced this type of movement in other vehicles.

 

At this point I don't know for sure if this is the answer, but when the auto trans is in the neutral position no clutches or bands are supposed to be applied. Of course when in park there is a pawl that is engaged into a pocket of part of the output shaft. If tolerances of clutch packs are so close even with no hydraulic pressure applied, the motion of the input going into the trans still gets transferred to the assemblies and ends up at the output shaft possibly resulting in attempted movement.
Like I said, I don't know this for sure, but it sure makes sense to me. Some trans components may have closer tolerances than others of the same model and that could be why two of the same vehicles may behave differently. I would sure like if a trans expert could explain if that could be so.