I agree but alot of people report about a 3-4 mpg increase when they go from a C6 to a ZF 5spd. I havent done the swap yet but I plan on it this summer.

 

but what about those of us who just want to go fast
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Ahh! Different priority!

JUST GO FOR IT!!

 

Some of the gain must be from the high power consumption of the c6 - I've read up to 60hp

 

Yeah I would assume thats where most of it comes from plus the 5th gear has to help a little.

 

so if you want to go auto, there are 3 options pretty much;

-the c6 which you have, a real tank and can take abuse, add a gear vendors PRETtY pricey. Also i dont think their worth it, the c6 torque converter will slip indefinitely all the time.
-the E4OD automatic, can be built to a godly diesel torque capacity and beyond with a lockup converter. direct over drive at cruising speeds, needs a breakout box (baumann) and some tweaking of electronics
-the AOD has a really nice overdrive, .66:1 i think with a lockup converter. great cruiser but get that TV cable adjusted! this leads to the bad rep and is frowned upon for longevity. can be built to take power though


the manuals;

-NP435 is a TANK of a transmission, boasting a tracor 6:1 low and 8:1 reverse with 1:1 direct.
-the RUG is an extremely light duty overdrive (.78 i think) transmission made for daily drivers with no need for huge power. aluminum case, very weak.
-the M5OD is a car transmission put behind EFI motors for the same purpose as the RUG but a narrower gear spread. same .78 over and WEAK
-the T-18/T-19 are related to the NP 435 being a work transmission, granny first and a cast iron case with 1:1 direct. very sloppy when worn in though
-the coveted ZF5 transmission is a godly combination of granny first (5?:1 ratio) and a .76 overdrive! have your cake and eat it, too! very hard to find, integral bell housing means MAKE SURE IT IS A SMALLBLOCK ZF5! came behind 300's and 351W's in f250 and 350's.

for a manual swap your gonna need a flywheel, 11" clutch, hydraulic throwout rams or mechanical ones, throwout bearing, pilot bearing, clutch peddles, linkages or hydraulic cylinder.

Am i missing anything?

the gear vendors will live happily behind any transmission if you were thinking it. think about a ZF5 with the .76 over and the .78 over of a gear vendors. .59:1! you can run a 5.38 gear to pull ANYTHING and get the same highway cruise as a 3.25:1 geared truck. in the neighborhood of 2000 rpm at 65 mph.

ENOUGH OF ME BABBLING to sum it up, throw a stick in, the c6 is a real power drain being it sucks at least what, 20 hp? your gonna need all the hp of that inline 6 you can grab.