OK, so now the main point I am trying to make. Lets say you throw a bigger set of tires on your D30-eqipped Jeep, go wheeling, and decide the front axle one-wheel-peel sucks. So,the obvious upgrade is a locker, right? Now, here is the deal: upgraded parts for a D30 and D44 are basically the same price. In fact, some parts such as lockers and R&P sets for the 60 aren't much more than a 30 or 44. The difference is, you have to swap in the 44 (or 60), while the 30 is already there.
So, now the question becomes: "Which is better in the long run, and if the 44 (or 60) is better, can I do the swap?" Well, certain manufacturers (Teraflex off the top of my head) make front axle bracket kits for this very purpose. All that is needed is a grinder (for fitting adjustments) and a welder. Granted, it is a PITA. You have to strip the housing, make careful measurements, tack parts in place, measure again, weld everything, clean it, paint, and assemble. However, assuming you have or can borrow the tools and you got an axle with the same gear ratio as your current one, the only real cost involved is the bracket kit (which you can carefully cut from the D30 if you want to be real cheap) and the locker that you were going to put in the D30 anyway. So, mostly we're talking extra time and labor. If you want to do it right, you will be changing ball joints, brake calipers, pads, and rotors in your donor axle, but depending on it's history the wheel bearings, diff internals, shafts, and joints should be useable as-is. If you want to keep using stock steering, all you are likely to need for steering parts is a tie rod and a couple ends (one regular, one with the hole for the drag link). There's another couple hundred. Once the brackets are welded on, the axle is assembled and painted, and you throw it in, you can run it as-is. If you break something, then you are upgrading parts on an axle that already has a strength advantage in every component (well, except the u-joints) over the D30.
This may not make as much sense at first, but consider the possible alternative: You have a TJ, and you throw an ARB in the D30 to eliminate the one-wheel-peel (you've already swapped a locked 8.8 in the rear, so you're golden there!). Boom, you break a u-joint and destroy the ears on the shafts, so you get a set of Superiors and CTMs. Everything is great, but now you really want to run 37's and do some harder trails. You get a brand new set of 37" KM2's, hit the rocks, and BANG! There goes another shaft. Superior warranties it, so you slam in the replacement and go wheeling. BOOM! There goes your R&P. What the heck, you wanted deeper gears anyway, right? You toss some 5.38's in both diffs, set the preload in the D30 tighter than crap to try and minimize deflection and keep the R&P alive. You hit another hard trail. No body damage, but this sucker has gnarly undercuts. No worries - you're easy on the throttle. You got the wheel cranked (no choice - it's the only line available), you wind it up against the converter a bit to get the front up over the undercut ledge, and BANG! There goes your long-side inner shaft! Luckily you have an ARB and tow straps - you limp it out, throw in a spare shaft (which, granted, is a heck of a lot easier with unit bearings, but it still sucks), and take the bypasses for the rest of the trip.
You notice on your way home that the Jeep wants to pull to the right a bit. Weird. Anyway, you get home, and after thinking about it, you decide you don't want to break shafts anymore. You call Superior and order 30 spline inner shafts, and immediately afterwards you call ARB and order 30 spline side gears. The stuff arrives, you throw it in, and hit the trails! No sooner do you get onto the obstacle when you hear the passenger side stub shaft detonate - you know, the one you stress fractured when your inner shaft let go. Only now, you're screwed. You just realize that your spare stock shaft is 27 spline, but your ARB has 30 spline side gears! Well, you have two choices: limp it home with a busted shaft, or swap the stock stub onto the intact chromo inner and take the bypasses.
The last was a trick: If you try to limp home with a busted stub you're wheel is gonna fall off and you will crash into a busload of kids going on a field trip. Why? Because an INTACT stub is needed to hold your TJ's unit bearing hub together. Without it, it risks separation because it was not designed to run without a properly torqued stub holding it together.
So, in reality your two choices are either remove the stub from your stock assembly and use it to hold your unit bearing together so you can limp home, or swap it into the Superior shaft so you can at least wheel the easy lines for the remainder of the day. Either way, you have to fix it when you get home. Luckily, you remember that MaxPF mentioned on Hummer4x4 that you can swap a JK unit bearing assembly onto the older D30, which lets you use the larger diameter stub shafts! So, after spending $500 (or more) on a set of JK unit bearings, and even more money on JK stubs (make sure you get the ones for the 1310 size u-joint, not the larger later ones!), you are back in business. No worries about breakage now, right. whoops! Wait a sec - when you are swapping unit bearings, you notice something funky with the inner C's... Its bent!!!! Dammit!!!!! So, you tear all teh outer parts off, press out the ball joints, get out the smoke wrench, a big-ass pipe, and a hammer, and straighten it up. Then you order a gusset kit, weld it on, put everything back together, and NOW your really back in business!!!
You hit the trails, and all is great. A few months later, you are wheeling, you drop out of your line, and get really bound up. Your buddy hooks a winch line to you, but even so you're gonna have to help get yourself out. Winch cable taut, you ease into the throttle, and BANG! CRUNCH! CRUNCH! GRIND! You realize you just grenaded your fragile little R&P. After an hour of work with a winch and hi-lift, you manage to limp out of the trail. Unfortunately, your axles spin all the time since you don't have hub locks that you can disconnect, so just as with your first R&P breakage, you end up on the back of a flat bed tow truck.
Now you realize you have hit a wall: There is no way to upgrade your D30's R&P. Once again, you have two choices: limit your wheeling to easier trails, or upgrade the entire axle. The latter option means you have to part it out, and at best you only recoup a fraction of what you have in it. Worse yet, you will have to spend all that money again on the new axle. Actually less, because you are not likely to break a R&P, nor will you need to upgrade unit bearings or buy a gusset kit for the inner C's. Also, on the bright side, the CTM u-joints will work in a D44 if that ends up being the upgrade path! And, you won't have to find another D30 to replace the one under your truck that has a nice smile
Anyway, that's my story and I'm stickin' to it! Actually, you will find a LOT of true stories just like that. Granted, plenty of people upgrade their 30 and it serves them well. At the same time, many end up upgrading it only to swap it out later, even though they don't do extreme wheeling. Axles are like money - nobody ever wishes they had less.
