Mj Rock Truggy Questions

[Matt S.]

Richard, I agree with the motor. I will probly be doind just that because there is NO other motor that has the low end power and RELIABILITY that is has. As well as the AW4. From what i can remember, you have the RENIX motor correct? Well, I just sold my jeep and it had the RENIX, the engine bay makes me uncomforable and could cause a problem with the tubing work that i HOPE will be done.

NO, i do not have the truck already. And I WONT be buying one until I finish my schooling here in Phoenix. But I plan on getting my entire designing done with math and all. Then begin wiht buying the pieces to build. I have a TON of time for this.

Basically, If you were to cut everything from the firewall forward off and everything from behind the cab off, thats what i am looking into. So I want to have a semi-prerunner body styled LOOK built for rockcrawling. I am thinking that if i can build a full chassis and incorperate the body into it, this would be very benificial for CA laws and such. And because I DO want to drive it on the street to wherever I need to go, I have to pass CA emissions and all that.

Full width 60's are probly what will end up under it because of parts availabilty and reliability. And with at least 38s, probly 40s, shaving is going to greatly help to keep up with the smaller axles.

For the lightwieght ideas, where i get concerned is WHERE the wieght is going to sit. If it is mostly tubular, most of the sprung wieght WILL be in front of the cab. Somehow i have to figure into the design wieghts to creat a blanced vehicle wieght, so the suspension will work much easier, and HOPEFULLY be balanced as well.


THANKS
MATT

 

[4ward]

Put your battery, radiator, tools, spares, etc. in the back. Unless you plan on doing completely flat rockcrawling, the weight bias seems to be a lot better with it towards the front. Just don't tell Tiny that

Sean

 

[Pete M]

Since you're in the "planning" stage, don't rule out the Unimog axles just yet. The Volvo portals are the ones that are rare. Unimog axles aren't really that hard to find and are reasonably cheap. (yes, they can be found in junkyards, but I recommend getting someone else to track one down for you ;-) Check out:
http://www.rockymountainmoggers.com/links.html#forsale
and scroll down (way down) to see lots of different companies that carry parts. Heck, they still make Unimogs and sell 'em in this country!
The stock 404 'Mog wears 37" tires (with an ungodly tow rating) and has a coil suspension already, so it's plenty strong and already has link mounting points and coil buckets. The only complication may be the torque-tube length, but even then, if you're starting from scatch you can easily design around it. I'm pretty sure there are companys that make torque-tube eliminators too. And with all that gear reduction, you can even get a 2.5L (another torque-biased motor) to help keep the front weight down. Besides, you'd have to shave the bottom *half* of the Dana60 off to even approach the ground clearance of the portal!
(I don't mean to be argumentative, I just want to see this Comanche *trounce* the other guys, not just keep up! ;-)
Oh, and I once saw fiberglass bedsides for the Comanche on the web. You might want to try an internet search for that.
Jeep on!
--Pete

 

[Matt S.]

(I don't mean to be argumentative, I just want to see this Comanche *trounce* the other guys, not just keep up! ;-)

That is SOO great Pete. You may have just helped me name the project.

Sean, so a 50/50 wieght distribution is not THEE most optimal way to design? Maybe a thred should be started on actual weight Distribution. This is why I am planning now. Do you think that a rear mounted radiator is going to sufficiently cool? I suppose i could then use a freakin HUGE radiator and big CFM fan(s) right?

The only complication may be the torque-tube length, but even then, if you're starting from scatch you can easily design around it. I'm pretty sure there are companys that make torque-tube eliminators too.

??? Sorry, dont really know what your talking about :confused1
What is torque tube?

I know of one company who is making fiberglass front fenders and a hood, think it is Rusty. But havn't been able to find someone who makes a fiberglass bed skin. If that isnt ganna work out, could always do a flat bed or some trick thing back there.

One More subject for the geniouses out there. Can and Will a front 4 or 3 link non panhard bar front suspension be worked around the deep oil pan of the 4.0?? And if that is possible, throw a 404 into that equation!! Do you think that pinion wouldeven clear the motor and undercarriage stuff?? I could see pushing that front half of the jeep WAY forward. I guess in theory by doing that, you could also GREATLY affect the wieght distribution? Because if the cab of the jeep is more central, including the engine and whole body work, I can clear the huge snout of the 404 And help on wieght??

THANKS
MATT

 

[Pete M]

Hmmm, I guess I didn't really know what one was either. I thought the name referred to the huge pinion, but I did a quick search to find a picture and I've discovered that the "torque tube" is a really long extension coming off the differential that apparently hides the spinning driveshaft inside or something to that effect. Very interesting. There's a pic on the right hand side:
http://www.killeraxles.com/html/mog__axles.html
And one of a conversion:
http://www.bc4x4.com/includes/thumb...e a regular differential.&title=Hulk!&sa=true
Then it doesn't matter, as you'll need to get the conversion kit either way. Here are some other sites I came across:
http://www.killeraxles.com (great site! Even has axle measurements on it!)
http://www.sorv.com/umcustom.html (has a conversion kit etc.)
http://www.exaxt.ca/ (deals in custom applications and other 'Mog axle stuff)
For the record, that Chevy on the Exact site was built by the man who’s truck I attribute with starting my obsession with Comanches. Rob Bryce! His Comanche was awesome! (I say was because he sold it, not because anything bad happened to it.) Here's the site about his Comanche:
http://www.bc4x4.com/ryeguy/ (scroll down and there's some links)
And some more info on the 'mogged Blazer:
http://www.bc4x4.com/fv/2002/hulk/
As to clearance up front, it will definitely be tight. (Another reason to build up a 2.5L! Remember, you don't need tons of torque from the engine when your axles have 7-point-something gears in them. If you fall back on the D-60s, then I'd say 4.0L all the way. Plus the 4 banger will be easier to cool too.) With a custom built tube chassis, I'm sure it can happen. I know three and four links have been worked around the 4.0L. Do some internet searches and see if you can find some of the portaled trucks and buggies out there to see what they did. I'll let you know if I find anything interesting. I really like the idea of scooting the cab back a bit. If nothing else, I bet it'll look cool!
I can't seem to find the fiberglass bedsides. :-( I know I saw them somewhere, but alas, they don't come up in my searches. Oh well, at least tube steel doesn't self-destruct when it touches rock. ;-)
Jeep on!
--Pete

 

[Matt S.]

Great links and information!! I had NO IDEA that 404s were so cheap!!!!! WOW. thats all i have to say. Deffinantly going to build around those, well i hope. Pete, remember that i am GOING to drive this on the road, whenever i get the chance. So unless that little 4 popper is charged, it wount do to well.

Another thing I can get some serious input on, if all of you arent bored, to PROPERLY begin my suspension design, I HAVE to decide on axles. If I go and design around portals, how does that suspension actions? Like the roll center of the whole vehicle, the anti-squat and anti-dive of the front and rear suspensions???

In my mind, if raising the SPRUNG wieght 5 inches, i can in theory get 5 inches of lift if STOCK suspension was used right? If that is right, then I will only need LESS than 4 inches of actual lift, if i am shooting for the lowest hieght with largest tire size. Maybe I am confusing my self on this. Maybe someone can clear me upon what EFFECTS that portals will have to how the suspensions works? If it does. Man I think I am lost now!

THANKS
MATT

 

[Pete M]

Yup, the further down the portals drop the wheel centerline, the less actual "lift" is needed. And don't forget that you don't need 44" tires with the portals. It'd be easier on all of your components if you design around like a 37" tire. You'd still have more clearance than 44inchers on a Dana 60.
In the July 03 edition, Petersen's 4whl ran an article (like last month or so) on how to design a rear four-link. I seem to remember that it listed a couple books at the end of it as references. If I can find it, I'll scan it for you. The house is extremely chaotic right now though (refinishing the floors), so you might want to check out the magazine rack at the store or you can order it as a back-issue at:
http://www.the-direct-source.com/Products.ASP?DEPT=53

With the axle being that much closer to the "frame", it really isn't that hard to integrate a track/panhard bar into the equation. This rig at Killeraxles.com has one:
http://www.killeraxles.com/assets/images/Axle_Parts_036.xxl.jpg

Exxact can build unimog portals with a Dana44 or Ford 9inch center section. That would allow you to locate the front pinion more to the drivers side and maybe allow you to cut back on the gear ratio a bit. I'm clueless on details, but I'm sure they’d be happy to answer any questions.

And don't underestimate using leaf springs up front. There are lots of ways to get absolutely sick articulation out of leafs now-a-days and they are infinitely simpler to set-up and control (when building from scratch). Here's a couple examples I came across:
http://4wheeloffroad.com/featuredvehicles/92058/
http://www.twistedaxle.com/vehicles/vehicles/samurai.html
It's been done with great success! With the portals, it'd probably be best to do a spring-under to help control the wrap. Then again, if you build a good enough anti-wrap bar, I guess it doesn't really matter.

I think what I'm getting at is the need to do some real world research by tracking down rigs that use some of the components you're contemplating. Check out the rock crawling championship rigs especially. I know there are some running portals. Anything this complicated is bound to be a trial-and-error-fest and the cheapest way to learn is by learning from the mistakes of others! ;-) Find out what each builder likes and what problems they way be running into.

Jeep on!
--Pete

 

[BrettM]

-quote-
Exxact can build unimog portals with a Dana44 or Ford 9inch center section. That would allow you to locate the front pinion more to the drivers side and maybe allow you to cut back on the gear ratio a bit. I'm clueless on details, but I'm sure they’d be happy to answer any questions.
-quote-



That would be a sweet way to go! I'm pretty sure the 9inch goes down to 2.50 gears and the D44 down to 2.73. I'm also pretty sure the hubs give a 2:1 reduction, so you could run an overall axle ratio in the 5.**s, which would be perfect for 37s.

Search for "JR" and his "Fat City Bronco" on PBB, he has an awesome buggy with Mog/9inch hybrid axles.

 

[Matt S.]

Thanks for those sites and stuff. The main thing that is of my concern right now and is slowing down my thought process a huge amount, is what changes mathematically that the hub center line / axle center line do to all my measurments???

Ex: Soild axle on 40" tires. Hub AND axle center line are both the same. 4 link is built around the Axle center line, i think. SO it is faily simple to properly link a solid axle.
Now you seperate the Hub and Axle centerlines 5"s from each other, what happens? THis is boggeling my mind! I KNOW what tires i want to run. I KNOW that i wont need as much suspension lift. I KNOW how much frame clearance i want. What sucks about that is that to find how much suspension lift i need, in comparison with portal axles.

I keep trying to make myslef think as if i was working with a stock vehicle. If portals went under a STOCK XJ, you could fit 33s without trimming. Thats 5"s of vehicle lift, with 0" suspension. I guess what i am trying to get at is I dont want to be TALL. I want to sit the same height as a XJ with 35s and 6-7" lift. This is tough to figure out when dealing with 40 inch tires/ 5"s of hub "lift".

My brain hurts. I know how you feel Beez.

THINKING...................................OUCH!

MATT

 

[Matt S.]

Since this post has pretty much died.

I think I have figured out the situation.

If 40" tires are being used, your axle centerline is 20" from ground. Now add the 5" portal box to that and the HUB centerline is still 20"from ground, but the AXLE centerline is now 25" from ground. UNderstand so far?

So to MAKE the axle centerline 25" of the first example. You must run 50" tall tires. Hope this is right, if it sounds wrong please correct me.

Well, hopefully this has openedsome ideas into people here, and can help expand the XJ/MJ world!!!!

THANKS
MATT

 

[Pete M]

Certainly sounds plausible to me. But I don't have any experience running portals or designing four-links. Everything that I could come up with would only be conjecture and theory. You'll still need to ask those individuals who currently run portals or have designed suspension links around them. Have you contacted www.exaxt.ca yet? I bet they'd know or at least may be able to hook you up with some prior customers. Also, I'm dying to know how much it costs to convert the center section to a dana44 or 9inch. Please keep me posted on what you find.
Jeep on!
--Pete

P.S. When in doubt, just start a new thread. If a topic changes course, sometimes it's best to begin anew with a more specific title.

 

[Pete M]

I found a page that has some decent pics of the Rockcrusher.

http://www.4wdandsportutility.com/features/03044wd_crusher/

Jeep on!
--Pete