Hi
There is always a lot of questions about axles and lifts on all wrangler forum and if the dana30 will hold up or not and so on. But rarely there is talk about the frame, transfercase and transmission.
So, how rigid is the jk frame? Can it take a lot of weight for overland travel? Are there common isue with the two different transfercase or do they usaully hold up? What about the transmission?
Best regards
The frame is without question the biggest and most rigid frame ever made on a Wrangler. Unlike the TJ or YJ before, the cross section of the rails are massive and they are also tied in with cross members from front to rear. I know overlander types seem to think they somehow carry so much more weight than anyone else but I can assure you that fully loaded, my JK weighs in at 7,000+ and the frame holds it up just fine. If there's a place where you might see issues, it would be in getting significantly twisted up on big rocks and on a regular basis. If you play really hard, you will see some twisting in the frame.
As far as the transfer cases go, they are effectively the same only the Rubicon's come with a 4:1 gear ratio. So long as you make sure to NOT have any driveline vibrations, they will hold up well.
The manual 6-speed transmission I had held up great for well over 110,000 miles and I still had the original clutch in when I finally got rid of it. The automatics seem to do well too or at least, the one I have seems to be.
I've heard of a few transfer cases cracking the housing. Never seen it myself so I can't tell you too much more
I have personally seen cracked and shattered transfer cases and one of them was on one of my JK's. This all was going on back about 8 years ago and what we found is that it ONLY happens when you have front drive line vibrations that you leave unchecked for too long.