6x6 Tech

[TJVigilante]

So I have grandiose dreams and ambitions. Sue me. :p

Anyway, I've decided that after I build my TJ to an acceptable level for local wheeling, I plan on tackling a 6x6 project. Not an M35Ax, but more along the lines of a LWB 1-ton van or pickup. I'm leaning towards the van for the interior amenities possible. but I digress.

The biggest hurdle of any 6x6 project is how to get power to the rearmost axle. I've seen a few ways of dealing with this issue. The most common I've found being a 1:1 transfer case unit hard-mounted to the intermediate axle, clocked in such a way to allow for a driveshaft to be passed over the intermediate axle down to the rear axle. it could be a standard transfercase turned around and using the rear output as the input, with the two front shafts driving the two axles.

If that's confusing, here's a thread:
http://www.patrol4x4.com/forum/showthread.php?t=112

front of intermediate axle:

Notice how the center output of a standard pass-drop t-case is the input here.

Side of center axle:


And the factory input becomes the output to the rearmost axle. this or the t-case is a dual-offset case (think landcruiser or Land rover) using the input to drive the center axle.

Another solution I've found is an NP205/200 combination, using the offset outputs of the NP200 in the NP205 case retaining its factory center output, giving you a t-case with dual rear outputs. One output would be into a two-piece CV driveshaft back to an offset rear axle. This allows for 2Hi, 2Lo, 4hi, and 4Lo, but no FWD. The previous arrangement would allow for an upgraded transfercase for strength. but this one would be easier to adapt with junkyard parts. I'm wondering if there are adapters out there which allow a t-case to be hard-mounted to an axle or if it would need to be custom made. I was thinking just having it done yoke-yoke with a steel frame bolted to the axle tubes and diff cover, but that would be one heavy pig. It would have to have started out as a divorced t-case with a yoke on each shaft.

Any input? Something like this would need quite a bit of planning and research so starting this planning now, with my level of skill, might be the best idea.

[93hummer]

Usa6x6.com has an intermediate diff that passes through the housing

[TJVigilante]

I was thinking about that, and it would require a modification to the center diff cover with a support bearing otherwise it could cause center pinion deflection and baboom. USA6x6....that's a love/hate relationship anyway, and I think they're out of business too.

I could always go the easy route and run toploader rockwells but i might as well just buy a camper M35A2 and be done with it.

[TJVigilante]

also in the case pictured above, I could use a ford HP60 front axle as the rearmost, giving me rear steer relatively easily. problem there is it would cause scrubbing and clearance issues with the center axle, so that axle would also need to be steering. That's some $$$$$$ in hydraulic rams, pumps, controls, knuckles, shafts, ujoints, etc. think the cost of just one bling steering front axle and triple that. Lots of money, lots of weight. Center of gravity would be low though.

[93hummer]

there is a really good 6x6 thread over on AK4x4network

[TJVigilante]

say no more...off to Anchorage! (forums, that is )

edit: I found it, and it doesn't have much more info than this thread does already.

Seems the gear-over box would be the way to go, but would have to be a homebrew thing until I find someone else other than usa6x6 that makes them. Even if they weren't bankrupt, with their reputation of late-delivery of leaking double-beadlock wheels, I wouldn't give them almost $3k for a gearbox that might not survive.

Their gear-over boxes had to mount to a 9" or 14 bolt with their removable pinions, though. I wouldn't want to run two 14 bolts and have zero steering in the rear...putting steering to a 14 bolt would be insanity.

[SHoppe715]

There was a guy on the m715zone that was building a 6x6. He was using the two rear outputs on a 205 route, offset rearmost axle, and ran that driveshaft past the mid axle through a pillowblock bearing on the axle tube. He also had a set of lockouts on the rearmost axle to disengage it if he wanted. It was also going to have a four-link coilspring setup on all 3. I never followed the build and what I saw was years ago.

[TJVigilante]

I think I saw the transfer case he used, but didn't see the finished product in any of my searches.

[sevenslats]

The first one that came to mind was the green T-Rex Dodge. BUt I see he has rockwells.
http://www.cardomain.com/ride/2645823

[Zukman]

You could go with a three or four row morse chain in a homemade case. Check out some swampbuggy forums from the south. I have seen setups like your wanting used for 52" tires with big blocks and chain driven.

[TJVigilante]

Hrm, that t-Rex sits pretty low for being on rockwells...but another issue I'd have is gear ratio options, which the rockwells really don't have. Factory 6.72 or 4.90:1. I'm wondering if 6.72 would be too low for let's say a powerstroke 7.3 turning 46" baja claws. I was thinking instead some 5:13 14 bolts.

A homemade chain-drive case would work if I had the fab skills. I'd think it would be easier for me to figure a way to brace an existing case to an axle than make one completely from scratch. I guess with enough time and writing down measurements, I'd be able to get the chain cogs and the case made at a machine shop...but that's $$$.


Just saving this here for future reference and inspiration. Would it be cheaper to exclude the center gear here and run a chain, if I were to create it from scratch?

[AKMark]

So top speed would be about 60 mph, not a big deal, don't think I'd want to go much over than in a 6x6.

Heck a Duece or 5 ton at 60 mph is pretty scary, especially if you have the windshield open.

[TJVigilante]

But at that 60mph my engine would be screaming at 2k...not good for fuel economy driving to and from the trail. turning 6 46's, I'd need all the help I can get.

I'm sure the deuce is scary but that's because it's got pinion brakes and skinny tires on the front so it'll be twitchy...big wide 46" mickeys should be a little more comfortable, maybe. I wouldn't want to go much faster than that anyway but I'd like to have at least a moderate engine rpm while doing it.

[93hummer]

you're gonna need some RPM to turn big tires at 60, unless you have a big block or turbodiesel. Mine runs about 2500 RPMs at 60 MPH with 5.24 gears and 42's. The 6.2 even with the pump turned up, K+N air filter, and straight pipe barely has the guts to go 60. Hit some hills and I lose speed quickly.

[AKMark]

2000 rpm at 60 is nothing. I agree with Tony that you'd need that to turn tires of that size.

With that big a tire, MPG shouldn't be a concern. Because getting much isn't gonna happen, no matter what gears you go with.

[TJVigilante]

It would be a 7.3 powerstroke if I were to do it...so 2k is nuts.

[TJVigilante]

eh, I could always go with a big block gasser which would be just fine at 2k...probably cheaper at the pump too nowadays.

[93hummer]

The only prob with big tires, big block and a heavy rig is the mileage will be horrific. Mine gets 11 mpg with 42's. 94-95 350 gasser hummers get 8-9 with stock tires, I think if I had a big block gasser with 42's it would be more like 5-6 mpg. So who cares right? Well offroading it means you had better be packin some extra fuel cans, and at 5-6 mpg, you had better have quite a few of them or make sure your trips offroad are very short and close to gas stations. There used to be a company called Offroad America that did 502 Hummer conversions back in the day before GM took over the brand and the Duramax became all the rage, a lot of guys arre still doing duramax swaps today. They did a lot of 502 Chevy crate engine conversions and every pic I saw they had 4-5 jerry cans on the back, and they offered fenderwell fuel tanks and auxilary tanks behind the rear bumper. I didn't realize why until I started thinking about it later.... Don't get me wrong, I love big block chevy's but I would never run one in an offroad rig for the single reason of fuel consumption offroad. on the road is a different story, you can usually find gas easier than diesel at most stations. my rig has a 25 gallon tank, and at times it is barely enough for some of the longer trails.

[ChevyKev]

... I think if I had a big block gasser with 42's it would be more like 5-6 mpg.

Possibly - in that heavy of a beast... However, in my Borther's carb'd 454 Blazer he gets 11 on the road - granted that is with 36's, not 42's.

I get 12 with a carb'd 350 and 38.5's and 4.88's

I know fuel injected rigs with 454's that get better fuel economy than with mine

However, with 6 42's ... I don't know anything will get great mileage as well, he will have the room for extra fuel... so this may be a mute point.
(kinda wish I would have thought about that before I typed all the above.)

[Zukman]

Hrm, that t-Rex sits pretty low for being on rockwells...but another issue I'd have is gear ratio options, which the rockwells really don't have. Factory 6.72 or 4.90:1. I'm wondering if 6.72 would be too low for let's say a powerstroke 7.3 turning 46" baja claws. I was thinking instead some 5:13 14 bolts.

A homemade chain-drive case would work if I had the fab skills. I'd think it would be easier for me to figure a way to brace an existing case to an axle than make one completely from scratch. I guess with enough time and writing down measurements, I'd be able to get the chain cogs and the case made at a machine shop...but that's $$$.


Just saving this here for future reference and inspiration. Would it be cheaper to exclude the center gear here and run a chain, if I were to create it from scratch?

You can cut cost with 1/2 steel plates for the front and back. The sides could be made from 1/4 or 3/8 flat stock. With the chain set up the you can run it dry and wet, the wet set up does't have to be sealed completely, you could run it greased instead of oiled.

[AKMark]

It would be a 7.3 powerstroke if I were to do it...so 2k is nuts.

Actually with 4.35 gears (which some have from the factory) they run about 2K going 60 down the highway with stock tires. It's not too much, especially if you find yourself heavy towing or with enough mods to make the truck darn heavy.

I still would impress upon you at that time that 60 mph would be about your top speed, ever, so even if it was going 2200 rpms, not a big deal.

[Zukman]

Josh, could help you out on bulding the box.

[TJVigilante]

Some video inspiration:
http://www.youtube.com/watch?v=D8qeJEgBp8w
http://www.youtube.com/watch?v=Ryz3eO1IB...re=related

those are 44" Trxus STS tires on that...doesn't look to be much room for 46's in the first side profile but later on it shows a good 6-8" of gap between the two rear tires, and 46's would easily fit under the front arches. Then I'd have to worry about finding a place to drive it where it's necessary. Stampede?

[SamuraiMike]

I've been toying with this idea too, with a twist...
Instead of locating the center axle with the rear, move it to the center of the rig & make BOTH the front & rear axles coordinated steering.
The old ARMY M561 Gamma Goats did this.
http://www.olive-drab.com/idphoto/id_photos_m561.php3
This will allow it to turn extremely sharp by pivoting on the center axle.
We all have had trouble climbing out of ruts, with both axles turning, It will pull & push itself up out of it.
I think it would be a killer set up... Who wants to help me build one???
Here's a great concept!!!
http://www.youtube.com/watch?v=aYfd4muY1Wk&feature=fvw

[TJVigilante]

That's definitely a more european look, I prefer the American-ish look of the tandem rear axles. it also allows for a full side door in the van, maintaining 100% utility of the platform.

There's another video linked with those two on youtube of the inside of the south pole ice challenge van, full interior, full seating, no cage. I'd change that, personally...the back area over the tires will be 100% storage for spare equipment/tires, tools, camping gear and coolers. Allows me to put three buckets in the middle each with a harness tied to a bar across the back...will also stiffen up the chassis quite a bit.