how big of a lift would I need...

08 sierra crew cab and i wanna put 24's on it with 38 by 14 by 24 khumo road venture MT's, just wondering how big of a lift i would need and if i would have to do anything to the drivetrain. Thanks  

You might want to drop the gears a little.Say to about a 4.56.  
Dying ain't much of a livin'
From my favorite movie.
Trucks...
1989 150(200k) 33 inch hawgs and a blown 302.
1995 Pathfinder(178k)and still going with 31s.
Bikes.
2004 Yamaha TTR 225,barly used.
Kawasaki 750 (26k) Not ran right since carbs rebuilt.
!972 Yamaha mini enduro.The niceest one I've ever seen thats never been painted.
New 2002 f150,fx4,5.4v8,after market tranny coolers and unirol tires.

how big of lift you think i would need  

A 6-8 inch lift should be good.  
Dying ain't much of a livin'
From my favorite movie.
Trucks...
1989 150(200k) 33 inch hawgs and a blown 302.
1995 Pathfinder(178k)and still going with 31s.
Bikes.
2004 Yamaha TTR 225,barly used.
Kawasaki 750 (26k) Not ran right since carbs rebuilt.
!972 Yamaha mini enduro.The niceest one I've ever seen thats never been painted.
New 2002 f150,fx4,5.4v8,after market tranny coolers and unirol tires.

More like 10-12 to be more realistic. That is if you don't want to trim the fenders at all. Figure the width of the tire and the back spacing of the wheel and then you will have a better idea. A friend of mine installs lifts at a dealership and has for about 14 years now and he said you could get away with 8 if you trimmed the fenders, 10 ir you don't go offroad or flex it too much and 12 will clear the whole package.  

Naw.I think he would be able to do it with a 8.I took the idea  that because he was running 24s that it wouldnt be a trail truck.More of a street/show toy.The 10-12 would be good off road so the truck could flex.  
Dying ain't much of a livin'
From my favorite movie.
Trucks...
1989 150(200k) 33 inch hawgs and a blown 302.
1995 Pathfinder(178k)and still going with 31s.
Bikes.
2004 Yamaha TTR 225,barly used.
Kawasaki 750 (26k) Not ran right since carbs rebuilt.
!972 Yamaha mini enduro.The niceest one I've ever seen thats never been painted.
New 2002 f150,fx4,5.4v8,after market tranny coolers and unirol tires.

even with the 8 inc lift he will still rub when turning like when entering a driveway from the street...it will rub a little cuz of how wide those tires are..with slight fender trimming it will work but the 10 inc would most probabley clear it perfectly...12 inc is too much for just 38s even if they are 14 inc wide....btw your gonna lose a whole lot of power if you don't regear your axles cuz those are some giant tires compared to stock!!! figure about a 5:13 ratio...forget about 4:56 those are a joke with 38 inc tires...even if it is just a show truck i bet it will look badass with 38s on 24s!!!      
Solid axle chevys can't be beat!
My dream truck: 73-91 chevy 3500 crew cab srw with dana 60/14bolt, 6 inc long travel lift with KING shocks, 37 inc tires and a 24v cummins diesel, nv5600 and np205

I threw the number 4.56 out there beccause I didnt no if he was running the diesel or the 5.3 or 6.0.I figured that number would cover it.Also I didnt know if he had any modes done t the engine.Also I wasnt thinking about the width(sorry that was my fault )  
Dying ain't much of a livin'
From my favorite movie.
Trucks...
1989 150(200k) 33 inch hawgs and a blown 302.
1995 Pathfinder(178k)and still going with 31s.
Bikes.
2004 Yamaha TTR 225,barly used.
Kawasaki 750 (26k) Not ran right since carbs rebuilt.
!972 Yamaha mini enduro.The niceest one I've ever seen thats never been painted.
New 2002 f150,fx4,5.4v8,after market tranny coolers and unirol tires.

Finder:
I threw the number 4.56 out there beccause I didnt no if he was running the diesel or the 5.3 or 6.0.I figured that number would cover it.Also I didnt know if he had any modes done t the engine.Also I wasnt thinking about the width(sorry that was my fault )

dont worry about it but even if he did have a diesel or the 6.0  any ratio less than 4:88 would be unacceptlble with those tires...if hes got a gas motor i would run the 5:13s if its a diesel the 4:88s sound good since they have limited rpm range already....it would be nice to know what kind of 08 gmc crew cab is it?? a 1500,2500,3500?? 4wd or 2wd....gas or diesel???  
Solid axle chevys can't be beat!
My dream truck: 73-91 chevy 3500 crew cab srw with dana 60/14bolt, 6 inc long travel lift with KING shocks, 37 inc tires and a 24v cummins diesel, nv5600 and np205

its a 5.3 SLE 4WD. got it in august and i havent done anything to it yet. not looking to do much offroading just driving around and taking it out on the beach (outer banks, NC)  

Okay.So what what I understand is that the 5.3 makkes 310hp.If you where only puting 33s on it then I'd say you where good.Buteven with the gear ratio drop its going to be pretty slow.If I where you I would look in to a air intake kit and a power programer.Those will give the truck some more power and mpg.I dont know what you want to spend so I'll throw the idea of headers and duels to help it in the acceration and the sound/mpg. Sounds like its going to be a nice truck.  
Dying ain't much of a livin'
From my favorite movie.
Trucks...
1989 150(200k) 33 inch hawgs and a blown 302.
1995 Pathfinder(178k)and still going with 31s.
Bikes.
2004 Yamaha TTR 225,barly used.
Kawasaki 750 (26k) Not ran right since carbs rebuilt.
!972 Yamaha mini enduro.The niceest one I've ever seen thats never been painted.
New 2002 f150,fx4,5.4v8,after market tranny coolers and unirol tires.

thanks for all the info. i think it came stock with 33's on it, i know they are pretty big because the wheels are 20's. im thinkin bout gettin a K&N intake before anything else, worth the ***  

air and exhaust are all good but gears are best for power and mpg. 38's go with a 10in lift and 5.13's.  

one question is it a 1500, 2500, or 3500?  

its a 1500