Portal Lift and Axle Swap

Homeward_Bound · **Posted:** Sat Mar 25, 2017 4:58 am

Been toying with the idea of a portal lift. However, I am a long way away from it if I ever get to do so. The idea is to replace the front with a 7.6" GMC IFS and the 8.6" rear. These axles were chosen since they have 2.73 gears available for those differentials. This high a number is needed after the 1.91 ratio in the HMMWV portals will bring the total final drive ratio to 5.21. This would be good for 37" tires since engine RPMs would be about 3k.

The biggest hurdles to overcome would be getting the computer to play nicely with GM ABS hubs, fabricating brackets for the portals, and placing the brakes outboard of the portal boxes since the HMMWV was designed for inboard brakes.

I think the proof of concept would start with swapping the front and rear for the GM differentials. The outboard splines are the the same at 27 so the use of KK or JK hubs should be ok. From there, deciding how high to lift would be trial and error to determine CV angles. For now, this is just an idea. But I haven't seen anyone talk about this yet. Just thinking outside what is currently available.

Myke · **Posted:** Sat Mar 25, 2017 6:01 am

For the money you can go sfa and be built stronger and more flexabld.

But please follow through on this, would love to see it.

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tjkj2002 · **Posted:** Sat Mar 25, 2017 6:16 am

Sorry but those diffs will not work unless you just want 1 forward gear and 4 reverse gears.To us HMMWV portals you will need to use reverse rotation diffs like the HMMWV uses.

Homeward_Bound · **Posted:** Sat Mar 25, 2017 6:20 am

tjkj2002 wrote:

Sorry but those diffs will not work unless you just want 1 forward gear and 4 reverse gears.To us HMMWV portals you will need to use reverse rotation diffs like the HMMWV uses.

Sorry, should have mentioned that there is a standard rotation available for the front and reverse available for the rear to correct the rotation issue. Since the normal rotations are reverse in front and standard rear.

tjkj2002 · **Posted:** Sat Mar 25, 2017 9:18 pm

Homeward_Bound wrote:

tjkj2002 wrote:

Sorry but those diffs will not work unless you just want 1 forward gear and 4 reverse gears.To us HMMWV portals you will need to use reverse rotation diffs like the HMMWV uses.

Sorry, should have mentioned that there is a standard rotation available for the front and reverse available for the rear to correct the rotation issue. Since the normal rotations are reverse in front and standard rear.

The 7.6 GM IFS standard rotation is also used in the H3,can't be used with HMMWV portal hubs.

Your getting confused due to many places using the incorrect terms like reverse rotation and standard rotation instead using reverse cut and standard cut.

You need diff that actually spin in reverse like the modified AMC20's used in the HMMWV's and they have the choice of 2.56,2.73's,and 3.08 gear sets.

Phil + Neela · **Joined:** Sun Oct 23, 2011 5:19 pm **Posts:** 73

tjkj2002 wrote:

Homeward_Bound wrote:

tjkj2002 wrote:

Sorry but those diffs will not work unless you just want 1 forward gear and 4 reverse gears.To us HMMWV portals you will need to use reverse rotation diffs like the HMMWV uses.

Sorry, should have mentioned that there is a standard rotation available for the front and reverse available for the rear to correct the rotation issue. Since the normal rotations are reverse in front and standard rear.

The 7.6 GM IFS standard rotation is also used in the H3,can't be used with HMMWV portal hubs.

Your getting confused due to many places using the incorrect terms like reverse rotation and standard rotation instead using reverse cut and standard cut.

You need diff that actually spin in reverse like the modified AMC20's used in the HMMWV's and they have the choice of 2.56,2.73's,and 3.08 gear sets.

Here's how you can avoid the reverse rotation issues, but it requires a Dana 60 and far more money than most people have laying around.

https://www.quadratec.com/products/52451_0010.htm?gclid=CJjJqLbP9NICFYNnfgodbxIMEw

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Homeward_Bound · **Posted:** Tue Mar 28, 2017 10:48 am

tjkj2002 wrote:

Homeward_Bound wrote:

tjkj2002 wrote:

Sorry but those diffs will not work unless you just want 1 forward gear and 4 reverse gears.To us HMMWV portals you will need to use reverse rotation diffs like the HMMWV uses.

Sorry, should have mentioned that there is a standard rotation available for the front and reverse available for the rear to correct the rotation issue. Since the normal rotations are reverse in front and standard rear.

The 7.6 GM IFS standard rotation is also used in the H3,can't be used with HMMWV portal hubs.

Your getting confused due to many places using the incorrect terms like reverse rotation and standard rotation instead using reverse cut and standard cut.

You need diff that actually spin in reverse like the modified AMC20's used in the HMMWV's and they have the choice of 2.56,2.73's,and 3.08 gear sets.

Ah ok. One reason I started this discussion, to learn more and fine tune the idea. So putting front gears in the rear and rear in the front wouldn't do anything to correct the rotation issue then?

Phil + Neela wrote:

Here's how you can avoid the reverse rotation issues, but it requires a Dana 60 and far more money than most people have laying around.

https://www.quadratec.com/products/52451_0010.htm?gclid=CJjJqLbP9NICFYNnfgodbxIMEw

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I've seen those. And yea, wicked expensive.

tjkj2002 · **Posted:** Tue Mar 28, 2017 11:11 am

Homeward_Bound wrote:

Ah ok. One reason I started this discussion, to learn more and fine tune the idea. So putting front gears in the rear and rear in the front wouldn't do anything to correct the rotation issue then?

Sorry but no.

You have to use purpose built diffs,flip the diffs(so many headaches there),or use different portal ends that don't require reverse rotation diffs.

tjkj2002 · **Posted:** Tue Mar 28, 2017 11:17 am

Phil + Neela wrote:

Here's how you can avoid the reverse rotation issues, but it requires a Dana 60 and far more money than most people have laying around.

https://www.quadratec.com/products/52451_0010.htm?gclid=CJjJqLbP9NICFYNnfgodbxIMEw

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If you actually need a D60 front you're likely running 40"+ tires and sticking $10,000+ into a D60 is not hard or uncommon.Around here a balljoint HP60 will run you $1200 min before building and a kingpin HP60 starts at $2000 used.

In contrast I have $5800 in my HP44 to run 35" tires.

JeepNCrowd · **Posted:** Wed Mar 29, 2017 7:34 pm

IF you do it let me know. I'd like a write up. I've been toying with this idea myself...

Portal Lift and Axle Swap

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