Wow. Lots of dis-information in this thread. Probably indicative of why I rarely come to mud. But, alas, someone told me there was a link to a good pirates thread on mog axles on this forum, so here I am.
I'll clear up the error's where I have seen them...
Error: You need a new t-case becasue the mog's have the ring gear on the opposite side.
Truth: Indeed, the ring gear is on the opposite side of the pinion from normal, and the main axle shafts turn 'backwards', however the rotation is corrected in the portal. There are only 2 gears in the portal.. the gear on the axle shaft which is turning 'backwards', and the gear that the wheel is bolted to. Mog axles have standard rotations at the pinion.
Error: 404's have helical cut gears, and 406's have straight cut gears.
Truth: Early 406's also have helical cut gears. At some point (I don't know when) MB went to louder straight cut gears as the helical cuts put side loading on the portals and can cause them to break. For the record, if you have a rear steering axle, you need to swap the portals side to side so the helical gears are moving in the 'strong' direction when moving forward.
Error: you have to modify the frame to clear mog axles.
Truth: this is totally old school thinking. Most old timers build lift into the suspension. The portals provide 5" of lift. Instead of putting your lift in the suspension or body, take advantage of the 5: in the portals. In TippyR, I have a grand total of 6.5" of lift... 5 from the portals, and a 1.5" body lift. The axle tubes are in the same relative position to the frame as the factory deisgn. If it wasn't for the 4 links and air bags, I could run 38" tires on mog axles on a totally stock sprung under leaf spring suspension. Now, before anyone points out my hypocrosy, I'll admit I chopped the front of my frame and lifted it 4" to clear the air bags. But I did this for the air bags... the axle itself stays below the level of the old frame height.
Error: IFS Sucks
Truck: IFS is not preferred for rock crawling becasue one wheel does not force articulation to the opposite side. With better center ground clearance, and better % of sprung weight, IFS offers some significant offroad advantages. I am sitting on a design for an air/hydraulic system that would both force the articualtion that IFS lacks, as well as provide lateral stability (like an ant-sway bar, but it doesn't limit articulation). Not sure if it would be 'legal' in the rock crawling competitions because it might be considered an 'active' suspension.
Other things I can contribute:
- Changing the offset/axle length of a 404 axle is a major hassle as the 404 axles are double tubed, and have not flanges/tube joints. With the flange on the 406/416 axles, tube lengths can be changed relatively easily. Exaxt did indeed move my front diff 9" to the right for a LHS offset for about CAD$600.
- the only thing that will break will be the portal itself, or maybe the gears. It seems the both happen at the same time, no one is quite sure which gives out first. The tips of the gears get sheared off around about the same time that the portal itself splits open. Mind you, this usually only happens in competition rock crawling situations with 400HP and a WOT at the other end of a long driveline full of gear reduction. Regular wheelin shmoe's like me shouldn't have much to worry about.
Other advice... Rob, if you haven't already, you need to speak with Mac or Rob at Exaxt Axle. You're practically neighbours, and they will give you the entire straight poop on the realities of Mog Axles.
the bottom of my frame, t-case, and axles are all at about the same height... 22 inches of clearance. I vote for Mog axles.
Peter Straub
