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post #1 of (permalink) Old 03-30-2001, 02:37 PM Thread Starter
 
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Portal Axles

after a previous post and replies from some viewers, i have been contemplating the portal axle idea. this is what i am thinking, although it may not be in any logical order: make a box with 3 gears in it that bolts to the axle housing using either the backing plate bolts (rear) or spindle studs (front) it would probably be best done on a D60 rear (or other 3/4ton) and at least D44 front. what i have drawn up in autocad would require a 16.5" wheel and maybe some offset. the axle shafts would need the cut-down and resplined to match the splines in the gears. the rear seems to be pretty easy, but the front could get complicated, being that there is steering invoved. if anyone has some picture of portals on Unimogs or other custom set-ups, especially front axle, please post them. thanks for any info or input! matt

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post #2 of (permalink) Old 03-30-2001, 04:29 PM
 
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Re: Portal Axles

Why go to all the hassle of making your own reduction boxs for a solid axle, when there are a number of trucks that already have them? I admit, there not very common in the US but even having some Volvo truck axles brought over would be cheaper then designing, the r&d, and building something new. You'll have enough to deal with the outrageous amount of axle wrap the boxes will cause.

BTW, Avalanchee has custom build portals and their only about 12,000 bucks from what I was told, they got to be out of their mind!!!!

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post #3 of (permalink) Old 03-30-2001, 07:53 PM
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Re: Portal Axles

Why use three gears? I think that two would be better, then you could just flip any standard rotaton axle upside down, and make a high pinion at the same time for about 1/2 the price! Look at the ones that Avalanch sells, they use a Ford 9 inch. Very low pinion, jacked way up with the 3 gear setup. Now use the same 9 inch, upside down, and use 2 gears. The result would be higher driveshaft angle, more ground clearance, and 1/2 the amount of friction form the use of less gears. At least that was my first impression to their axle. OK, now start using your cad program, and make some serious money! Just kidding, but what is wrong with this idea? Think of the old VW bus. It used the same principle. They swapped the ring gear to the other side of the transaxle, and put a reverse rotation gear reduction at the axles.

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post #4 of (permalink) Old 03-31-2001, 12:49 AM
 
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Re: Portal Axles

You'd starve the pinion by flipping the housing, high pinion axles are designed to prevent this from happening.

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post #5 of (permalink) Old 03-31-2001, 06:56 AM
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Re: Portal Axles

I have heard that before, but I don't believe it. Maybe on an interstate for very long periods of time, when heat build up is a problem. But I don't think that would ever happen off road. Did you ever see how much fluid that a ring gear will pump when it is turning? Saab even puts a filter screen on the diff cover, and it works very well. I think that you could just raise the fluid level a bit to help compensate. I have looked at the pinion oil holes in both a high pinion 60 and a standard. There is one on the top, and another on the bottom, the only difference is the one on top is larger.

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post #6 of (permalink) Old 04-02-2001, 10:22 AM Thread Starter
 
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Re: Portal Axles

didn't think of flipping the axle...my idea was to make them bolt on to existing axles, may not even need to remove them from the vehicle. thanks for the ideas! matt

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post #7 of (permalink) Old 04-02-2001, 12:06 PM
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Re: Portal Axles

Adding a portal axle "gear box" to a existing axle would most likely result in the new box ripping itself from the axle. The amount of extra force generated by the lever arm of the offset is serious. At the very least you'd need to weld it to the axle tube. Plus you'd have to add some sort of anti rotation device, like a 4-bar. With out this you would have unbelievable spring wrap.

As for the Avalanche portal axle, the reason they use the ford 9" center section is for ease of service and its light weight. If Dana axles had those qualities, then I bet they would have used them. Plus the 9" has an extra pinion bearing. Also with a 2:1 reduction in the hubs, you don't need that beefy of a diff. Oh, the reason they are so expensive is because each axle and all the parts are custom machined. I imagine as they become more popular they might come down in price. (only front axles are 12k rears are cheaper 'cause no steering stuff).

If you want to see them in action, get down to the Easter Jeep Safari and look for the next generation Sniper.


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post #8 of (permalink) Old 04-02-2001, 02:00 PM
 
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Re: Portal Axles

-snip- Oh, the reason they are so expensive is because each axle and all the parts are custom machined.-snip-

IMO, the reason they are so expensive is that Avalanchee charges way to much F___ing money. Everything they sell is about 40% more then the next lowest price. If it was 40% better then the next guy, that would be fine but its not.

-snip-(only front axles are 12k rears are cheaper 'cause no steering stuff)-snip-

OHHHH, in that case all buy them <G>

As you can probable tell, I've been burned by Avalanchee before.

-snip-If you want to see them in action, get down to the Easter Jeep Safari and look for the next generation Sniper.-snip-

No thanks, it makes my head hurt looking at what they spent my money on.

I still say, just swap in a mog or volvo axle.

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post #9 of (permalink) Old 04-02-2001, 02:49 PM
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Re: Portal Axles

Hey, I'm not justifying the cost, Just the design. I work with the guy who designs and builds the axles for Avalanche (kind of an OEM supplier). I personally would rather buy another Jeep for that kind of money. Who knows how much the markup is on the axle once Avalanche gets their hands on it, I figure it's kind of rude to ask my coworker directly. Clearly, being that he doesn't build axles full time is an indication that they're not paying him THAT much for them.

The problem I have with 'Mog axles is that they are chain driven. I'd go gear drive any day, for strength.

If you're hell bent on the DIY, maybe you could use the guts from a 203 or 205 case for the gears.

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post #10 of (permalink) Old 04-02-2001, 03:19 PM
 
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Re: Portal Axles

I'm happy with the 60/14bolt that i have. It might slide over rock but with a little taller tire, no big deal. (I may not be hell bent but if its at all possable, Yes i do DIY, I think its a large part of this Hobby)

I just can't see the point of designing something thats already in production.

Whats going to happen to the center of gravity by rising the axle height?
Both of the axles I use are about the same weight as my engine, so to a point they are holding the jeep to the ground. On off camber situations, would'nt the portal axles be at a disadvantage.

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