Supercharge or gear swap?

[ASTAR]

Ok so I Love my new Hummer but the mileage sucks (I knew it would so no biggie) and the power is lacking. I went from a 700hp/1400ft lb tq Dodge diesel truck to this and man, what a difference. I am not expecting to have a hot rod like my Dodge was or the tow master it was either but....
Something I can't deal with is the lack of being able to hold 4th gear on the freeway at speed. If I am doing 70-75ish and there is the slightest incline, it slows down (cruise on or off) and then downshifts to 3rd to hold speed. Its constant. I have 38" tires on it now and I know that made it much worse. I did the small engine upgrades (see signature) but it still sucks badly.
Ultimately, I would like to gain seat of the pants power and can't decide how to do it. I was thinking about putting 4:88 gears in it but wonder what will happen to my fuel mileage. It was around 11.5 before lift and now around 9 with the lift/tires. Maybe a supercharger (yes I have been searching) but the transmission scares me. I don't want to dump another 10 grand into this thing between the upgraded tranny and supercharger itself. What will the MPG do with a supercharger if I did though?
I also tow about 7k once or twice a month. Not a big deal but if I hit a hill, whoa, it hurts. The MPG drops hard and the power is seriously deprived.

So whats the word from the masses?
I figure I can install the S/C if I go that route and maybe I can talk GM into helping out some with a tranny if I smoke it? Maybe? I'd also return the Airaid and Hypertech if I supercharge (money back) since it's only been on for about 2 weeks. Gotta Love Summit!
If I do the gears, I'll have to have them done as I don't know how to "set up" gears.
Seems the gears would be a lot cheaper and more warranty friendly but will I feel the power again? Will I have horrible MPG since RPM's will be higher in O/D on the freeway at 75mph? I'll also be keeping the Airaid and Hypertech if I re-gear.

Any input is appreciated, I can't deal with this downshifting!!! HELP!

Thanks.

[KenP]

You're complaining about mileage, lack of power and inability to hold OD on a grade. Put the 4:88's in and you'll have that times 2.

Install the SC with a proper programmer and that will really help. But that also will bring other problems with it.

PM these guys:
HUMMERcustoms.com/TAZ
or
HGW

[rocketw19]

i would suggest the magnuson super charger with the stock program. adds alot of power but still dependable no tranny problems for me. they have after market guys settin up super programs to get the most out of there trucks but i have no clue how reliable they are. or if the factory warranty is still there. gas milage is gonna suck no matter what but you should of know that already. my milage droped from 10 to 8.3 do to me pressin harder on the gas peddle i like the fell of the SC.

[Screeper]

I have 38 inch tires and did the gear swap to 4:88s which I highly recommend. I am very pleased with the result. I think your MPG will improve as you are pushing a lot or tire and gear with that tranny in your current set up. I used a hypertech programmer to correct my speedo and got it right on, although I had to play with tire size as it only went up to 4:56. I recently went up against a non lifted factory tired 05 and pulled on him to 55 where he started to come back but seat of pants was a huge improvement. I dont downshift at all at 70 and only occasionally at 75. At eighty I am spinning 2500rpm exact. My mpg went from 11.7 before the lift,tires and gears to 10.2 after. The mpg goes to hell after 70 mph. I am obviously a fan of gear swap. The torque strain on the tranny and engine pushing those tires with a supercharger as got ot be immense. I think the heat and wear have got to be an issue. If your looking for pure fun, and not mechanical longevity, I dont think you can argue with a supercharger.

[KenP]

Our mileage went UP after getting the SC from the 10s to the 11s.

Screep, with the 4:88s, you're turning a higher RPM across the entire band. I don't understand how you could get BETTER gas mileage.

I do see the truck performing better.

[Screeper]

It comes down to how hard the engine is working and where you are placing your torque curve for optimum fuel economy. Imagine your transmission got stuck in third gear and you were driving in the city. The engine would be straining constantly to get the truck moving. You would have to be hard on the gas and most of your MPG would go into the converter to generate the torque need to move the truck. Big tires have the same effect as taking away your first gear. Changing the gears allows the engine and transmission to not "see" the size of the tires. My 4:88s with 38 by 15.50 tires in gears 1 through 3 pretty much have the same rpm range as factory. Anouther way to look at it is like a bicycle. Imagine you and anouther rider are about to go up a large hill on mountain bikes (resistance) You both are equally strong and the bikes are identical with the exception that your bike is stuck in its top gear. The other rider can drop into his lower gears and pedal much more easily. When you reach the top of the hill the other rider is fresh whereas you are exhausted. Your bike would have been the best and required the least energy for long long flat rides but stop and go or up hill it required the most energy. It basically comes down to allowing your engine and transmission to work at the RPM where it is most effective. I am no expert so I hope this is somewhat understandable if not a bit wordy.

Al