Portal axles pros/cons, why/why not?

[Ura-Ki]

Nope, ALL have the same flange to flange! Unless they added spacers at the flanges or most common, run wide off set rims!
All UNIMOG axles from the model 406 in the early 70's on up are 76 inches flange to flange!

 

[MikeInOr]

Cons: MPG will go to hell. Top speed will probably be severely impacted. Parts availability, more parts = more problems. Much cheaper to put a lift on and fix the geometry, a good gear guy can rotate an axle pretty easily.

Are you thinking of a dedicated off-road truck? I doubt you would like a daily driver with portal axles. I have driven 1 Unimog... it topped out at a bit over 50mph, foot to the floor to do 55 on level ground... nothing I would want to drive on the highway.

To me the biggest advantage is getting the lowest center of gravity with the highest ground clearance.

 

[Ura-Ki]

Cons: MPG will go to hell. Top speed will probably be severely impacted. Parts availability, more parts = more problems. Much cheaper to put a lift on and fix the geometry, a good gear guy can rotate an axle pretty easily.

Are you thinking of a dedicated off-road truck? I doubt you would like a daily driver with portal axles. I have driven 1 Unimog... it topped out at a bit over 50mph, foot to the floor to do 55 on level ground... nothing I would want to drive on the highway.

To me the biggest advantage is getting the lowest center of gravity with the highest ground clearance.

There all kinds of fun though! The one I drive from time to time will do 80 on the freeway flat out! With the B 5.9 Cummins, it don't do that bad on fuel, about 18 MPG if ya keep yer foot outta the Turbo!

 

[edzz]

Portals can be fun. At car shows before driving out always check under your truck for kids that maybe playing there.
One of the problems is finding people to go out and play with. If you have a very capable vehicle you need to be running with similar vehicles so if you do get stuck or break down you're not depending on vehicles that can't help with a rescue.
The DeadBull Pinz in the picture suffered from improperly repair work, after a repair the portals were not properly installed. While rock climbing stairsteps the motor stuttered, when the motor fired the torque caused the front right and middle right portals to turn on the axel. Luckily a couple of the big Mogs were present to extract him and drag him back to camp. The took ~4 hours to get him to camp that was less than 15 minuets away normally.
The Pinzgauer in most of the shots was mine. The others are some of the old crew.

 

[Ura-Ki]

Portals can be fun. At car shows before driving out always check under your truck for kids that maybe playing there.
One of the problems is finding people to go out and play with. If you have a very capable vehicle you need to be running with similar vehicles so if you do get stuck or break down you're not depending on vehicles that can't help with a rescue.
The DeadBull Pinz in the picture suffered from improperly repair work, after a repair the portals were not properly installed. While rock climbing stairsteps the motor stuttered, when the motor fired the torque caused the front right and middle right portals to turn on the axel. Luckily a couple of the big Mogs were present to extract him and drag him back to camp. The took ~4 hours to get him to camp that was less than 15 minuets away normally.
The Pinzgauer in most of the shots was mine. The others are some of the old crew.

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Yea, and DON'T break that Tatra, it will sit where it lands unless you have another Tatra to fish it out! Ask me how I know that! Even a pair of UniMogs couldn't pull it!

 

[edzz]

Yea, and DON'T break that Tatra, it will sit where it lands unless you have another Tatra to fish it out! Ask me how I know that! Even a pair of UniMogs couldn't pull it!

Not a Tatra

 

[CamoDeafie]

I have a Kia Sportage 2wd for a daily driver. I'm thinking of a 2nd vehicle eventually for just off roading fun and such.... I figure it depends on the axle gearing, Like Urak-ai said, it looks like some can go faster than the mil standards do....

I'm thinking maybe a relatively cheap 1980s Cherokee or 1960s-70s CJ (parts truck or something) and putting Unimogs underneath, but nothing else other than wheels big enough for the Unimog axles, and maybe make sure the engine is a 6.0 straight 6 instead of a wheezy 4 banger...... In theory, it should be real simple to put them on, right? CJ is probably easiest due to having leaf springs on all 4 corners, whereas the XJ Cherokees have that coil spring front suspension.....but that should not take much work? Are the Unimog axles similar to a D44 axle in terms of mounting points?

 

[MikeInOr]

I have a Kia Sportage 2wd for a daily driver. I'm thinking of a 2nd vehicle eventually for just off roading fun and such.... I figure it depends on the axle gearing, Like Urak-ai said, it looks like some can go faster than the mil standards do....

I'm thinking maybe a relatively cheap 1980s Cherokee or 1960s-70s CJ (parts truck or something) and putting Unimogs underneath, but nothing else other than wheels big enough for the Unimog axles, and maybe make sure the engine is a 6.0 straight 6 instead of a wheezy 4 banger...... In theory, it should be real simple to put them on, right? CJ is probably easiest due to having leaf springs on all 4 corners, whereas the XJ Cherokees have that coil spring front suspension.....but that should not take much work? Are the Unimog axles similar to a D44 axle in terms of mounting points?

A dedicated off road fun rig is the way to go in my opinion. I have a 76 Scout w/392, ARB lockers front and back, 4.11 gears and 33 Buckshots. I don't like driving it over 65 on the highway because of the low gearing it puts me at about 2900 - 3000 rpm which is high for a IH motor. When it hits the trail the low gearing is pure fun! I can get myself into a pretty good jam with the lockers open... then just engage the lockers and idle on out. Stay away from full time lockers in the front diff... you loose a lot of ability to steer.

For a dedicated trail rig portal axles would be great! Highest ground clearance with lowest center of gravity allows you to go a lot of places most daily drivers just can't. I never cared for the jacked up really tall trucks, too big, too tall, much too high of a center of gravity for a trail rig... they are more of a mud bog rig IMHO.

When you are ready to buy look around for trail rigs for sale... you can usually pick up a pretty good rig for a fraction of what the owner has spent on parts... if you know what you are looking at!

You don't need a lot of power if the rig is light weight. You can kind of float over stuff the bigger rigs have to plow through. I had a 45 Ford Jeep when I was young... it was amazing where it would go the my friends newer bigger rigs couldn't. Unfortunately the original jeeps weren't made for a 6'3" person with a 34" inseam... it was incredibly uncomfortable to drive anywhere on the road... but a blast on the trail. I bought the Scout to pull the jeep... then said the heck with the Jeep!

Like said above off-road buddies are a must! There is safety in numbers! I had a buddy with a CJ5 running a worn out 304.. he rebuilt a 401 out of a Wagoneer and bolted it into his CJ5... it was a beast!

BTW: Be careful when looking at portal axles... many require the drive shaft to spin in backwards because the direction is reversed again in the portal gears. If you go this route just make sure you have a rig with an engine you can easily convert to spin backwards! You know... just change the plug firing order on the distributor.

 

[CamoDeafie]

I'm 5'7" with 28-29 inseam tall torso, short legs. I'm aware I dont need much power, but its always nice to have... was looking at either lifting and then convert to 4wd the 2001 Sportage but its not worth the costs and time and effort at the moment... and theres the suspension/steering geometry to figure.. and the fact there aint a thing like bolt on portal axles for such a tiny 1 generation-only thing (later Sportages went to a car based platform with none of the off road capabilities that the 95-2003 Sportages/Retonas did, such as body on fully boxed ladder frame, actual 4wd with solid rear axle and IFS, and dirt common 5x5.5 wheel stud pattern ) oh I could in theory put different stuff on and weld up and so on, but again, not worth the costs, time, or hassles

A CJ3-5 rolling chassis with a moderately decent shape tub, depending on what engine... a diesel would be fun swap, a much newer buick v6 from a RWD GM vehicle (Pontiac and Chevy camaros before their retirement and resurrection), or a Chevy 4.3 v6 out of a Blazer/Astro... mated to a 5 speed with 2 speed transfer case, and Unimog axles... what size wheels do the "small" Unimog 404s accommodate? Perhaps the later disc brake equipped 406s? 16.5" same as H1?

 

[MikeInOr]

Do you understand that if you bolt a set of Unimog axles under a CJ when you start the CJ, put it in first gear and let out the clutch you will be traveling backwards? With a T18 tranny you will have 1 really slow forward speed and 4 reverse speeds?

 

[CamoDeafie]

Do you understand that if you put a set of Unimog axles under a CJ when you start the CJ, put it in first gear and let out the clutch you will be traveling backwards? With a T18 tranny you will have 1 really slow forward speed and 4 reverse speeds?

I'm aware that I would need to reverse the differentials if needed, or at least flip the transmission setup somehow so that driveline can spin backwards

 

[MikeInOr]

I'm aware that I would need to reverse the differentials if needed, or at least flip the transmission setup somehow so that driveline can spin backwards

OK, I didn't want you to have a rude surprise on your first test drive! LOL!!!!

 

[CamoDeafie]

Hm a rear engined CJ might be fun to see LOL

 

[L84Cabo]

@L84Cabo ; you dont mean widening the track of the wheels(left to right) as opposed to streching the wheelbase (fore and aft)? I think the bolt on portals increase the tracking width by quite a bit... which would require either a deeper backspaced wheel set, or maybe a change in some of the steering components to compensate for the increased track width?

I only meant that if you add portals, which in turn may raise the COG, it MIGHT affect the stability of the rig, assuming you don't do anything else to it. I do not know enough about these things to know if they would increase the tracking width for sure...which would obviously help add some stability back to the rig.

If YOU know for sure that portals would increase the tracking width, you are miles more knowledgeable than I am on these things. I was simply just speculating on what some of the negatives MIGHT be.

 

[MikeInOr]

Hm a rear engined CJ might be fun to see LOL

If you are interested... I believe the common fix for the driving backwards problem is to grind the welds where the axle tubes enter the pumpkin (Differential housing), rotate the pumpkin 180 degrees, then re-weld the axle tubes to the opposite side of the pumpkin. Ring and pinion gears are usually bevel cut (cut at an angle to the face of the gear) to increase contact area and decrease noise. When you flip the pumpkin to run backwards you are running the ring and pinion in the opposite direction they were designed to run... usually not a problem as far as I am aware but something you should be aware of. You also need to be aware that the pumpkin will be upside down after this operation. Most likely not a big deal... but I believe Unimog axles have a mechanically activated differential lock... which will now be on the bottom of the pumpkin instead of the top. Pumpkins also have breather tubes that may start dumping gear oil if located on the bottom of the pumpkin instead of the top. Your drain plug in the pumpkin will also now be on the top of the pumpkin instead of the bottom of the pumpkin... kind of inconvenient!

Fixing the axle geometry on a lifted rig is done in much the same manner but the welds are ground, the pumpkin is rotated a few degrees (instead of flipped over) and re-welded. "Back in the day" Mr. Scout down in Eugene was very adept with gear work like this and he had a special fixture he used when doing such work to keep the axle tubes perpendicular with each other... axle tubes at an angle to each other obviously don't work that well.

Another axle swap potential problem you should be aware of is not all differential housings (pumpkins) are centered between the wheels. On my Scout the differential housing is about a foot or so to the driver side. So one front axle is considerably shorter than the front axle on the other side of the pumpkin... same with the rear. Other vehicles have the pumpkins offset to the passenger side and others have the pumpkins centered. Something you should be aware of when you are looking at swapping axles from other rigs, you can introduce some weird drive line angles which might result in problems!

 

[41mag]

You can buy a running Hummer for under 5K!

#2 son just had to have one several years ago; his experience demonstrated 1) it;s REALLY hard to actually BUY a 'running Hummer' for under $5K;
and perhaps more important,

2) it's really IMPOSSIBLE to keep one running for under $5K;

given his was a full on .mil surplus original model (I forget the actual model ID #s) despite enthusiasm & a largish budget available to stabilize & make 'reliable' his steed, impressive as it was, perhaps the best that can be said from his financial discoveries, was his HMMR was cheaper than a divorce would have been.

 

[CamoDeafie]

So the Unimog axle pumpkins are shaped that the pinion ring cannot be flipped to reverse the driveline rotations?

 

[Ura-Ki]

So the Unimog axle pumpkins are shaped that the pinion ring cannot be flipped to reverse the driveline rotations?

Depends on which model you are working on! Here in 'Murica, folks take Dana 60's center sections and graft the Unimogs portals to the ends, making gear changes possible and increasing strength! You loose to gain doing this, you loose the factory hydro-lock differentials and have to ether add air lockers or some other means to lock your diffs!

 

[CamoDeafie]

I'm looking at options... maybe its best to run shortened/narrowed GM 14 bolts or Dana 60 axles and the Axletech portal units even if they're massively heavy....... because the Axletech units have 4 gears in each piece for maintaining standard rotation.... if it still ends up needing to modify, weld, etc the axle parts in order to make them work with the portals and the sizes I'm wanting to go with...
On the other hand.... maybe I can live with banging the differential pumpkins everytime I find a rock taller than the ground clearance

Or live with taking out a loan and just acquiring a Pinz... how much maintenance do they need compared to "modern" passenger vehicles? I know the AM General Humvees need a LOT of maintenance

 

[Ura-Ki]

I have seen a shop thay specialises in Mog hot rodding use the 2 1/2 Rockwells with the Mog portals, they do a bunch of other cool stuff to them and go racing in big endurance races in Europe, they win all the time with their custom built trucks! I have a U-4000 high roof cab I am going to use on my LMTV project, no one wanted this cab because of its size, but it's perfect for my project! I hate my LMTV cab, it's junk and a huge waste of space!