I have a 99 F250LD with the 4R100 tranny. Is the "L" valve body the same? Or is it valved for quicker and firmer shifts?

 

I would ask Gregg Evans.
You can find him here.

 

No, the lightning is set up to shift firmenr than any other 4R100, the diesels, V-10s and Navis get a little less and the NA 5.4 gets a little tiny line mod valve and less pressure on the lower circuit. The Diesels, V-10s and Navis get less pressure on thye upper circuit on one bore, or the other way around, I get them confused. Now that I ponder it, the softer lower is the Diesels and V-10s and Navi, the softer upper circuit is the 5.4 NA.

G