Joined: Mar 2009
Location: Travis AFB / Fairfield
For all automatic Mustangs 96-04 with the stock transmission, "1" will hold first gear as long as the lever remains there. It will run to fuel cut-off and remain in first. It will not shift out of first, PERIOD.
The same is true of "2". It will hold second gear, PERIOD. It will not start in first and then shift to second: it will hold second.
The 4R70W is not negatively affected by using "1" or "2". It will be damaged if you are revving the engine and drop it into any gear. This is called "neutral bombing", emphasis on BOMBING.
Other transmission designs are generally not as robust as the 4R70W's, so I cannot comment on their ability to hold "L", "1", etc. with any reliability...
1995 5.0L GT, T-5, Black, 'vert.
1996 4.6L GT, T-45, Laser Red, 'vert.
1997 3.8L V6, 4R70W, Laser Red, coupé.
1997 3.8L V6, T-5, Black, coupé w/ sunroof.
1997 4.6L Cobra, T-45, Black, coupé.