What rpm does a t3/t4 start spooling? What kinda of hp are you guys meaning buy ALOT HP when running a LS trans.. It seems like the GSR is all around the best trans because of shorter gears, which is faster accell which is faster spool. Would a GSR trans be geared to low for my turbo so traction would be a issue? Of course suspension products would be a big help. My car has Type R suspension under it. My question is roughly what would a LS trans 75mph mpg get vs a gsr trans, what would the difference be in mpg at 75? Maybe building a gsr trans with a LS 4 and 5 gear would be the best bet so you would have fast accel on the bottom end and still be pretty decent for cruising on interstate..