[V8] V8 kickdown

[Lawrence Gorman]

I have two 3.6L 90V8Qs.  One has the original 90 4spd automatic and the 
other has a 93 4spd automatic.  The  90 tranny drops down one or two speeds 
when I floor it and gives me the power I need for merging onto the 
interstate, etc.  The 93 tranny doesn't behave the same way and fails to 
drop down more than one gear beyond 65mph when I floor it--feels more like 
a 4cyl. between 65 and 75mph.  Questions:  What governs the kickdown points 
on these transmissions?  There isn't a kickdown switch per se. Were there 
design modifications to the 93 trannies (or other 4.2L automatics) that 
would cause them to function differently when connected up to a 3.6L?