Everyone talks about or actually replaces the stock D35 in their jeeps, why is it that it is rarely talked about changing the D30? does the 30 hold up that much better because of the design of front axles even though they are smaller then the 35?
I'd like to know too. I've been sitting the fence on whether I want to build a D-44 or a D-30. From what I've gathered the two downfalls are to the D-30, the smaller pinion and the unit bearing outers. In the latest Jp on the shelf at Barnes and Noble they had an upgrade to D44 outers using new knuckles. That just leaves the R&P. I haven't seen a 4.56 R&P hold up to anything greater than a 35" tall tire consistently to say that you can't break a gear set. I think PrerunnerXJ has gone through a couple of sets and one of my co-workers was on his second set before he did a Hi-9 front.
Cliff notes: If you are building an axle for 33-35's it may hold up. if you're going to anything bigger get either a 60 or a 609.
Because the biggest weak link in a 30 or 44 is the same, the u joint most of the time. Yes once and a while people will break r&p but if you are smart start with a hp30 out of a xj. The hp30 is very close to the same strength as a lp44.
My guide lines;
36's or below hp30
37's and above 60 or if you have money 609
driving style goes a long way, if you push the stupid pedal alot yeah a d30 is gonna explode, but if your driving style is a little laid back and you don't go full on assault on an obstacle right out the gate, you can make a hp30 survive moderate abuse, lockers and types of axle shafts used play big in survivability as well.