Dana 35:
- if you upgrade the axles to 30 spline and cromoly they will be stronger than the D44 axles
- the housing will most likely need a truss if you go > 33s (from what i read they tend to bend as the housing was not meant for that much torque or heavy tires)
- there is still a matter of R&P size which is small(er), some say that is also a weak point and will break or wear faster with the bigger tires
- i went with the 30 spline cromoly and Auburn ected for the rear which is an LSD with an electric lock, heard bad and good about it but it was only $575 so i decided to bite the bullet - not installed yet so i can't offer any advice on it
- I chose the max R&P available for D35/D30 which is 4.88 (or lowest ratio if you wish), you can't go higher than that in the D35/D30 due to ring size
Dana 30:
- there is absolutely no reason to run an LSD upfront since the YJs/TJs are 4x4 and not "all wheel drive" (4wd full time), so you will only engage the front if you're wheeling or on snow/ice - for the latter you really don't want an LSD as it will make your Jeep go straight but the rear lsd will help.
- according to all reviews i've seen about the auburn upfront and the manufacturer recommendations you shouldn't use it on D30 if you have the disconnect axle on the pass side, apparently it would wreck the diff or the clutches in it. Also some reviews i read were saying that it would not disengage even with the 1 piece pass axle, but to be fair they had replaced them with a new reviewed version which fixed some of the issues (according to the same forum posts and reviews i looked at) - based on these i decided to pass on the idea of an LSD for the D30
- a lot of people (including myself) have only good things to say about the D30, it is a solid axle - failures usually occur on the u-joints but those can be upgraded
- same like the D35, the D30 can be upgraded to 30 spline cromoly axles but the hub potion will still be at the same diameter as stock, however i have not seen reports of any failing at the hub (maybe because the way they are bolted on there, not sure).
- imo for the front you should use a selectable locker and replace the 2 piece pass axle to the solid one (in case you have a 2-piece)
- i don't think the D30 needs a truss, but it will definitely not hurt at all (the tubes are shorter than the D35 ones so that probably gives more overall strength i suppose)
Upgrading to 30 spline for both front/rear requires upgrading the diff
EDIT: fixed couple of spelling mistakes above