I'm EXTREMELY happy with mine (ETH). I have a mild gear clash in 3rd gear that many of the 6 speeds have; test drive so you'll know what to expect. I also have a mild wander, but after 21,000 miles have decided it is not really much more than slightly loose steering. Wish it wasn't there, but it doesn't get me fully spun up any more. As to options, some I highly recommend:
#1 Trip Computer. Yeah, it is not 100% accurate, you should still manually calculate your mileage. But it is extremely useful for "relative" information. I can tell immediately whether I'm getting better mpg in 5th or 6th at a given speed, and I also use it to keep track of engine hours and true "average speed" on each tank of fuel. You can see immediate effects of hills, headwinds, speed changes, etc.
#2 Snow Plow Preparation group. Yes, snow plows in Texas. Down here in the South, we call them "brush guards" or "winches". This option sets you up for more weight hanging over the front bumper, and gets you the NV241HD (heavy duty) tranfer case.
#3 Add EGT and boost gauges. I strongly believe in post turbo; others believe just as strongly in pre-turbo. If you are not towing and not BOMB'ing, post turbo is where you want to go to more accurately monitor turbo cooldown, which will take forever on a hot Texas day. Search the old posts on this topic, you'll find the opposing opinions and their reasons. Read between the lines - the strongest opinions for "pre turbo" are coming mostly from those with heavily modified rigs. Lots of trucks don't even have this guage, so if your engine is stock and you're not towing up long hills, then most of the "pre turbo" arguments don't really apply, and what is left is protecting your turbo, for which post turbo mount excels. But like I say, read the posts so everyone doesn't have to respond to this message to tell you how full of it I am.
#ad
#4 4WD. Big decision. Major cost adder; major hit to your mpg. But I am willing to pay both prices because this truck is heavy in the front and gets stuck easily. I get a bit over 18 mpg at 70 mph; drops off rapidly as speed increases (about 1 mpg for each 4 mph). Can easily get 20+ cruising at closer to 60 mph, but it takes forever to get somewhere.
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2001 ETH, QC, LWB, 4WD, 3. 54, SPA Pyro & Boost, K&N RE-880 w/foam pre-cleaner, ARE Z-series Cab-high shell, Rear ARB locker, and all kinds of synthetic fluids...