how can i check the tranny fluid on a 01' s-type?
3.0 engine.

Here is the drain & fill procedure for the Ford 5R55N transmission.

I would add one word of caution and try to remove the small allen or torx plug in the drain/stand pipe before draining the fluid. If the small level plug is too tight and strips then you will have no way to correctly check the fluid level. I always keep a spare drain/stand pipe (XR852333) because some are overtight or the locking sealant sticks it tight. The later ones should be TORX and early ones were ALLEN.

The TEMP range for fluid level checking is stamped on the rear of the gearbox.

bob gauff

Absolutely right! I keep one on hand as well. Though honestly, I haven't had one give me any trouble in 3-4 years.

Should i drive the car before checking it?

No, do not drive first. You know I thought something was missing from that procedure. The level should ideally be checked at 100 deg. F, but the allowable range is 80-20 deg. F.
Driving the car first will most assuredly take the temp too high. The intent is to use a scantool capable of monitoring the trans temp while doing the level check. Not everybody can do that.

Good luck!

Just use a non-contact laser thermometer on the pan and it will be plenty accurate.

bob gauff

And attachment is for a 01' s-type?

Yes sir! Applies to all S-Types thru 2002 model year, unless you happen to be somewhere in the world that they used a different transmission that I am not aware of. All in the North American market used the Ford 5R55N gearbox.

Note: The reason for checking ATF fluid level at a partic. temperature is because the viscosity improvers in the fluid expand considerably when hot. This is how viscosity improvers work, they are intended to expand.
Leedsman.