Syntethic will NOT cause the 4R100 to shudder. MERCON V will screw up the trans, and that includes any fluid that has both MERCON and MERCON V ratings.

Many people believe the MERCON is non-synthetic and MERCON V is synthetic. That is not true. You can buy either MERCON or MERCON V in conventional, blend, or full synthetic.

I use Mobil 1 synthetic ATF in my 4R100. It has a MERCON rating and no MERCON V rating, so it is fine in the 4R100.

As for which trans island-guy has, check the blue tag on the driver's door jamb. Under the letters TR is either an "E" or a "U." If it's an "E" it has the 4R100. If it is a "U" it is the 4R70W.

The 4R100 requires MERCON and the 4R70W requires MERCON V. It also will say which fluid on the transmission dipstick handle.

Ford stopped installing torque converter drain plugs very early in the 2002 model year, so chances are you don't have one. There is a better way to change the fluid, though. Read this:

https://www.ford-trucks.com/article/...nsmission.html