Coming from a guy who drives a mostly stock M1009, and Loves the thing to pieces (ie once got rid of some looney-toon girl because she didn't get along with his truck
) I can tell you that it will cost a bajillion dollars and just as many man hours before you can take that thing off road without having to worry about breaking anything.
First of all, we have a 3/4 ton 5900 LB truck, on little halfton axles. We've got GM 10 bolts, which I consider roughly equivalent to D44's. They're great for jeeps, Toyotas, and other 1/4 ton's (My buddy has a nice little S10 with the ZR2 offroad package that is a lot of fun) and they work fine under our trucks on the road, even in conservative gravel pits, but they are not strong enough to really beat-on off road without concerns about them breaking. You will want a D60 in the front and a GM 14 bolt in the back, or another pair of axles along those lines. They were designed to be under heavier trucks, and can take more of a beating. If you really want to rag on it, I'd say you need even bigger.. like deuce or cement truck axles (outside my knowledge.. for now).
Now, as soon as you upgrade your axles, you open up a whole other can of worms because heavier axles have lower gear ratios. So you're going to need an overdrive transmission or something like that if you want to drive on the highway (which you and I probably need, as we use them as our daily drivers) at a reasonable speed without over-revving your 6.2 diesel (some will disagree with me here, as many people drive their M1008's on the highways, but I wouldn't recommend doing that to a 6.2 if I depend on it and want it to last as long as possible. Please take no offense, M1008 highway drivers).
So now you're going to replace the transmission too.. But all GM's 4 speed auto's are a different size than the TH400, so you're going to need to move things around down there. And if you're into it that far.. you might as well address the old 6.2 diesel under your hood that is not renown for longevity and only makes 155 horsepower (thankfully she makes good torque though). And how about that chain driven aluminum transfer case?.. Hmm that could be a weak point too
If you really think about what you want your truck to be able to do (As I have been doing for years now) you're probably going to want to reinvent the whole truck. Now some would ask "is it worth it to put so much work into a 20+ year old truck?". My answer would be a resounding "Yes", for emissions reasons. Depending where you live, you can't put older engines into newer vehicles because they will then make more emissions. Personally, I think this is stupid, because I would never put a 2010 engine in anything except maybe a sports car. They are lighter, cheaper on fuel, higher performing - nut not nearly as reliable as the old fully mechanical stuff.
I'll get down off my soap box now.. Anyways, I'm still a young man in working hard to make my money, then spending it all on school, driving my M1009 to work/school everyday.. but if/when I graduate I could actually afford big toys. I will probably one day be the owner of a 1986 M1009 with a Cummins/Caterpiller/Detroit Diesel/Mack/Haven't decided engine, backed by an equally ridiculous 99 speed 10-stick transmission/transfercase and 2-3 even more ridiculous axles. (6 wheel M1009 with 4 wheel steer would be soo cool)
Although, by that time I may find myself a Deuce, 5-Ton, and some more toys to do the same with......
But that's because I'm crazy. My advice to you - If you're not mechanically inclined (just guessing because of previous posts, please do not take offense - I personally believe any man can do anything if he wants to learn bad enough<even if it takes him 7 years, sucks up all his money and makes him miserable>) buy a nice little trailer for your M1009, and a quad(ATV, etc). They're cheap, FUN, they do crazy things, and when they break - you can still get to work on monday!
Just my $0.02 - Wishing you the best. Take care.
