Unimog axles cj 5 4 link suspension

[cj68man]

Hey,i recently baught a parts unimog for 900$ and I am using the axles off of it becuse they are only 55.5 inches form wms to wms and extreamly strong. I am using the same coils out of the unimog with new shocks and custom control arms. I love the Traditional look of jeep/willys and trust that it is a great design. I want to keep the narrow track dimensions as close as possible to stock (only 1.75 inches wider on either side with unimog axles) i am keeping the wheelbase 81 inches. Makes for a great trail rider.
The question I have is, inorder to keep my 81 inch wheel base maintained I need to have custom control arms configured. I am doing a 4 link in the rear using rustys custom shafts. Does anybody know the best way to find out where to mount the brackets on the chassie to have the best flex and proper geomotry? thanks to anyone who can help i appreciate anything you may be able to throw my way.

[Jim_Lou]

Great project! There are several calculators on the net. Someone will chime in with a link.

I'd suggest that you reconsider keeping stock wheelbase. The Mog axels have an extremely long pinion shaft that on a CJ5 will necessitate a pretty short driveshaft. The resulting U-joint angles will reduce suspension travel, especially if you add any lift.

Also check with BurnedBronco on this board. He's put Mog axles under a YJ.

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He's on the Bronco board more often, I think, but your best bet is to PM him. He's a great guy and will be glad to offer advice.

[LEVE]

I love your idea... as I really like UniMogs... There's a good Utube video showing a CJ5 and UniMog axles at:

YouTube - Willys CJ5 unimog axles 4.4Turbo

[cj68man]

here are some quick shots i got of the jeep its in the rebuild process now to fit the unimog axles under it.

[Jim_Lou]

Yeah, you're definitely going to have to move the back axle back. What transfer case are you going to use? Getting rid of the T-Case drum brake will get you a little room, but not enough, I think.

[cj68man]

Im not planing on chaning a thing. my plan is to have a dirve shaft that is hard to break by landing on it. The pinon conversion spits the yoke adapter two inches past the splines on the axle. The drive shaft which i already machined to be shorter becuse of the novak adapter to moojunt the dana 18 to the sm420 needs to be cut again even shorter. I realize my driveshaft is going to be tiny but my goal is to make the drive shaft the flex point and only 10 inches long so it will sit almost horizontal between the transfercase and pinon conversion this way if I land on any rocks back there there is a little change of it hitting my drive shaft. What do you think about this im curiouse to hear. thanks

[Jim_Lou]

Ten inches eye-to-eye? It surprises me that you can even get that much in there. If you get forty degrees of motion out of the front joint, that's less than 7" of total travel, and if it starts out horizontal you only have 3 1/2" of droop, which isn't much. I don't know how much angle a CV joint can do, but someone here does. Your best bet might be to use a Birfield joint - that will tolerate a lot more angularity than a double-cardan.

I guess an important question is what do you plan to do with this? You're going to an awful lot of work and expense here, so I'd guess that you want to build a pretty serious off-road Jeep. Building it in such a way that you have to limit the suspension travel is counter-productive to that goal.

[cj68man]

I want to enter top truck challange this year or next. You make a great point about a joint that can articulate more. Ill look into that. I want to run the new tsl's comning out late november. they are 43 14.5 20 TSL SX. Perfect tire. Not a 52 like most guys there but i have the portals to more than make up for it. When you say "Building it in such a way that you have to limit the suspension travel is counter-productive to that goal." are you saying that becuse of the drivshaft issue we are talking about or are you referring to the topic of control arm lenthgs and placemnets. this i would love some input on becuse i have no idea how my desighn will work. It seems like this is a common feeling umongs other wheelers who do a simular modification. I have the brackects all figured out and it looks like its going ot be easier than I had actiully inticipated. I have been doing a million calculatiuons and simulations that I make on graph paper or using the internet sites but nothing is like obviously usaing it in real life. I fell that all of my angles, and values are correct and I am ready to go with it. though always willing to listen and learn about things that may make me change my build up. I will get fully adjustible control arms flex joints both ends and play around with brackts if need be. Thanks for all your input. keep the ideas and thoughts coming it helps me a lot to see what i will be creating in the next couple of months. Thanks for the help and support, josh

[Jim_Lou]

My concern is the U-joint articulation. You can only bend a U-joint so far. A cardan joint (cross & yoke) or a double-cardan (constant velocity) is weaker the farther it's bent. A birfield joint, as typically used in front-wheel drive cars, can go farther but, for reasons I don't understand, they're seldom used on 4X4 drive shafts. I've seen specs on how far various joints can bend, but can't recall the numbers. You should search for that - it'll be important.

And I guess you've figured out that the links have to be attached to the frame approximately straight to the sides of the T-case U-joints. That will minimize the shaft length change with articulation. If you manage to get significant travel, that will be important. Do it wrong and you'll pull the slip joint apart.

[spook2]

Something else you might want to reconsider is keeping the stock mog coils. Mogs are heavy pigs and the coils reflect that. I'd be concerned that a relatively light weight CJ5 sitting up there might as well be sitting on solid blocks as sitting on those coils. Might want to keep your eyes open for some TJ take-off coils.