some 03+ tranny's have a FDR altering diff...previous to that its just the "straight ratio" diffs that do not change FDR
the 04+ ULEV L26 GP's have a diff that turns the 3.29 fdr chain equipped tranny's into a 3.05...the taller gear than a standard 3.29 NA trans is what helped GM get the ULEV certification
throw that diff into a 2.93 chain trans and youll get 2.84 iirc
I know I did the calcs for the 1/2 mile event with the hd/non hd "same ratio" diffs maxing us at 165 in 3rd at 7k where the 3.05 would let us take 3rd gear to 17x at 7k
mostly a pie in the sky math exercise its a viable option since we only have a 3.29 FDR GMR chain...
the 4t80e is the trans with all FDR adjustments via the output/differential planetary gears, yer a 1hr diff swap away from 3.11, 3.48, 3.71 fdr's
