AXLE UPDRADE

[XGarfX]

Highway speeds I'm just under 3k, the 4.0 really likes the higher rpms. The engine doesn't struggle as much and its in its sweet spot, you can actually feel the engine "smooth" out at the higher RPM on the highway. Just yesterday I was loaded down with well over a few hundred pounds of gear, spare parts and tools pulling long hard grades all the time the xj would hold strong in OD. I used to always be in 3rd gear but now my xj actually can hold OD on most any hills without even struggling.

Have you ever broke shafts yet? If not I would just say grind out the stock 30 shafts for full circle snap rings and put some new spicer 760x u joints in there. 75% of the axle shaft breakages in the 30 I've seen on the trails are because of the half moon c-clips spitting out and allowing the caps to walk out, once the cap walks out the trunion of the u joint smacks the axle shaft yolk ears and destroys both the joint and the shaft. With snap ringed spicer 760s, locked, 4.88s and 33s on some pretty tough trails I have not had a shaft failure. On the trail yesterday 2 guys broke 30 shafts on 33s, both of them were running the stock half moon c-clips to hold the joints in.

 

[JAS]

I run 4.88 on just 31's now. 70 MPH is about 2750 to about 2850. I have no issues with it other than I think I notice my drive line vibes a little bit because the drive shaft is turning a bit quicker.

I recommend the counter sunk holes on the Ruff Stuff cover. It prevents the center chunk from flexing. This will prevent gear failures under heavy loads long past where a stock covered chunk would spit them.

 

[sunburned]

My axle damage (all done with 4.56 gears):

D30:

cracked u-joint caps on both shafts (locked front, 32's, stock shafts/ujoints)
broke 5 teeth off ring gear (locked front, 35's, RCVs crappy gear setup)

8.25:

broke 2 teeth off 2 different spots on the ring gear (locked rear, 35's, stock shafts)

So I've regeared both axles twice and upgraded pretty much everything there is to upgrade on both axles. Turd polish ain't cheap lol.

 

[XGarfX]

Sunburned, when you cracked the u joint caps were they on their way out as it is? I'm having a hard time picturing a brand new u joint with good (non pulverized needle bearings) cracking a cap. Not saying I don't take your word I just was curious the condition on the u joint itself.

Heres a write up for anyone looking to upgrade their u joints to 760s w/full snap rings -> http://www.therangerstation.com/Magazine/May06/dana35_ujoint_snapring.htm

Its not an xj but its the same concept and the same size u joints.

 

[sunburned]

The u-joints and shafts were stock '98 parts. Jeep probably had around 130k miles and I had been wheeling it a few times a year for two years. When they cracked, it was my first wheeling trip with the ARB in the front. Each u-joint had multiple cracked caps. However, I never pulled them apart after I pulled the shafts. Probably will sometime to have them as trail spares. Bought 760 joints and full clips to put in the spares, but with RCV's I probably won't need them.