[kaisen]

If you want to stick around $20K, you're going to find more of the 'old' bodystyle (2000-2006) than 'new' (2007-up).

So, in the old bodystyle you have the choice of the Chevrolet Suburban, GMC Yukon XL, or Cadillac Escalade ESV. There is really no difference between the Chev and GMC until you look at GMC's Denali version. The 1/2 ton versions of the 'normal' Chev/GMC are 5.3L V8, 4 speed auto (4L60E) and have the Autotrac pushbutton transfer case with neutral and low range, but also allows for automatic engagement of 4WD. There was an all wheel drive option with the lower trim levels but not the norm. All Denali/Escalades had the 6.0L V8, same 4 speed auto, and they were all wheel drive, no 4WD option (no low range, no locked ratio). Denali/Escalade all had AutoRide levelling suspension, which was also a popular option in the regular trim levels. The only 1/2 ton Suburban to offer the 6.0L (AWD) was the 2006 LTZ trim level, again mechanically identical to a Denali or Escalade.

There is little difference, mechanically, between the 2003-2006 5.3L and 6.0L. Both are good motors that will darn near last forever. The 6.0L had/has more occurance of piston-slap, sometimes pronounced (although it didn't hurt the longevity of the motor). The fuel economy difference is almost nil if apples-to-apples equipped, which is hard to do....some of the mpg difference is the all wheel drive system of the 6.0s. The 2006 Sub 6.0L LTZ AWD, Denali, and Escalade were all rated 12 mpg city and 16 mpg freeway. The base 5.3L 4WD was rated 13 mpg city and 17 freeway. Most buyers wouldn't consider one mile per gallon a difference between buying one or not. Oh, and you'll also see that the Escalade recommends premium grade fuel, which is ONLY a marketing ploy to advertise a higher power rating for their 'premium' Caddy.....there is no physical difference in the motor, just mapping software that can take advantage of higher octane when you're using it. But it's still as happy with regular fuel as any other 6.0L.

If you're not towing there is very little reason to get the 2500. But one non-towing reason is to get the 6.0L motor with the 4WD transfer case, not the permanent all wheel drive. A 6.0L 2500 4WD in 2WD mode gets better fuel economy than a 6.0L 1500 AWD, if they have the same diff ratios (typically 3.73). The 3/4 ton also has a full-floating rear end, bigger bearings, bigger heat-sink brakes, and rear leaf springs instead of coils. The 8.1L is a great motor, but you have zero need for it.

Common issues are usually pretty small potatoes. The fuel pump is in-tank and relatively labor intensive to change out. Figure $200 for the part and $200 for labor. They usually last 100-150K miles, but when they go it leaves you stranded. Gauges, as someone mentioned, can go haywire from the circuit boards warping. They can be fixed. Tamas Oprah (sp?) here on the board rebuilds them. It's not very expensive. The rest is just typical wear item stuff like brakes, wheel bearings, seals and gaskets, etc. Look for leaks and it looks like it's been leaking awhile, figure it damaged whatever is leaking (diff, axle, TC, trans, etc). Parts are cheap, and plentifully available used and aftermarket. Mechanically, they are one of the most common platforms in the world. They build a million of them every year.

My current '03 Sub 2500 has 260K miles with original engine, transmission, transfer case, and differentials. And it runs like a swiss watch. Everything works. It still looks good. Still the original fuel pump too. This is not atypical. You'll find several 200-400K mile 00-06 Subs for sale on CL and eBay.

IF you can find a 2007-up, the interior fit and finish is generally better, and the dash is more attractive. The third row seat is easier to remove because it splits in two pieces (the older ones are HEAVY) but less comfortable because of the split. The power liftgate is a nice option, as is the back-up camera....neither were available in the old-body. Mechanically, there is very little difference between the old and new....they use the same frame. But, the aluminum 6.2L 6 speed AWD drivetrain in the Denali and Escalade is OMG awesome, if you can afford one. The later 5.3L versions also got 6 speed automatics, and it made a real-world difference in both performance and fuel economy. The 2007-2008 5.3L E85 4WD versions had aluminum blocks where the non-E85 were cast iron. Mostly just weight-saving and a small difference in handling.