There are two main issues and one ancillary issue with a D-30 that need to be addressed to run any tire larger than 33".
The first is the stiffness of the axle assembly. A D-30 with 37's is going to flex like a wet noodle torsionally and axially. This is not good for the life of any TAD, and is also hard on pinion shafts, as the ring gear tries to force itself into the pinion. Hence, Joachims tooth skipping incident. We have found that an OX locker is helpfull, but not a cure all, because of its extra beefy cover. It really seems to help hold things together.
Second issue is brakes. D-30 brakes suck ass, in case you haven't noticed. They are marginally safe with 33's, and not safe at all with 37's. There are numerous ways to adress this with WJ brake parts, but it's neither simple or cheap.
Third issue is gearing. 4.88 ratios in D-30's have been known to fail before 760 joints. Do you really want your weak link to be the ring and pinion? So if you want strong gears and want to run 37's, you are forced to run 4.56's, which is not near deep enough for highway or crawling use. They might be OK if you have a deep geared manual trans and an Atlas or Klune-V. As a comparison, I think 4.88's and 35's are about perfect, and i have an NV4500 with a 6.3 to 1 first and a 27% OD. I spin 2800 on the freeway in OD going just over 75.
In conclusion, by the time you get through building up your 30 to handle 37's you can have yourself a 44 that allows you to safely turn up to 5.38 gears, is a much larger, much stiffer assembly, has good brakes stock (spectacular with aftermarket, twin piston calipers), and the ability to easily run high steer.
Good luck!
CRASH