The Model 20. This may surprise a few of you!! - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-06-2000, 01:07 AM
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The Model 20. This may surprise a few of you!!

Ah yes, the Model 20. How many of you knew it is still in production and widely used in the United states? Well, if you're THAT good, then you also know that the Model 20 is the front and rear axles of all Hummers/Hum-Vees. Yes, i too, was surprised.

(Above information obtained from ARB, while dreaming of air-lockers)

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post #2 of (permalink) Old 12-06-2000, 01:13 AM
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Re: The Model 20. This may surprise a few of you!!

doesnt the hummer have 4 wheel independent suspension. maybe they just used the houseing?????

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post #3 of (permalink) Old 12-06-2000, 02:07 AM
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Re: The Model 20. This may surprise a few of you!!

Yes, the hummers are all independent suspension. Inboard of the prop shafts (CV shafts) they are, however, Model 20s.

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post #4 of (permalink) Old 12-06-2000, 04:49 AM
 
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Re: The Model 20. This may surprise a few of you!!

just the carrier section, not the whole axle.

gimme one of those surplus zexel torsen things!

that should quell the dana 44 dispute for a while.



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post #5 of (permalink) Old 12-06-2000, 07:04 AM
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Re: The Model 20. This may surprise a few of you!!

Yep the Hummer does use the AMC20 as it's diff. However the Portal axle system that it uses has the torque expended in the wheel assembly, not at the diff like the Jeep. It means the diff can be ligheter. It's quite a nice system. It's used on Mercedes UniMogs, Pinzgauer and Halflinger. All of these vehicles are more than capable off-road and a lot of thier reliability and capability is due to portal axles.

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post #6 of (permalink) Old 12-06-2000, 07:50 AM
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Re: The Model 20. This may surprise a few of you!!

Damn, Remy, not again!

Oh, OK, so what you're saying is that the Model 20 is a great axle, it must be for the Military to use it in the Hummers, right? Let's compare apples to apples. Only the center section is used, so none of the shortcomings are there, the weaker axle tubes, the smaller shafts, less splines, weaker bearings, and smaller brakes. So therefore all we're comparing is the center pumpkin, which is the Model 20's only strength compared to the D44, and it's only marginally larger.

Oh yeah, keep in mind the Military frequently uses the parts supplied by the low bidder. If they were really concerned about strength and not cost, they'd use the D60 centersection.



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post #7 of (permalink) Old 12-06-2000, 08:23 AM
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Re: The Model 20. This may surprise a few of you!!

Jeepn', The use of the AMC20 in the Hummer makes perfect sense WHEN coupled with the portal axles. WIth portal style axles the diff and the drive shafts can be very, very light in compaired with other vehlces of the same class. The other reason for use of portal axles is to gain ground clearance.

Take a look at:

http://www.west-4x4.demon.co.uk/portal.htm

http://www.4wdonline.com/Steyr/Pinzgauer/6x6.html

And for fun:

http://www.prosperopublishing.com/fh...pinzlinks.html

Good reading, but IMHO it would not be a bad thing if DC brough out the portal axle on a Jeep. IF they go to the rice-burner concept like many of the ohter companies have done it would go miles in making it a lot more capable and reliable. But I think the military did a fine job of engineering the Hummer drivetrain, it's strong and reliable under varied conditions.

Happy Holidays and Safe Jeepin'

Larry
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post #8 of (permalink) Old 12-06-2000, 08:36 AM
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Re: The Model 20. This may surprise a few of you!!

From what I've read, there's more to the model 20 use than its being good. AM General who makes the Hummer used to be part of AMC who made the CJ with the crappy versions of the Model 20. Take a long look at the front of the Hummer. If you narrow it slightly it becomes a CJ! They're direct cousins and you can't escape the fact that the army needed something bigger to carry missles and use IFS/IRS suspension, so they took the best at the time...the CJ...and redesigned it. [img]/wwwthreads_images/icons/wink.gif[/img]

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post #9 of (permalink) Old 12-06-2000, 01:48 PM
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Re: The Model 20. This may surprise a few of you!!

Moreover, the AMC20 centersection on the Hummer is geared with 2.73:1 gears (and the torsion locker, if not equipped with a different locker)...so it's got the beefiest gearset possible. And it's turning the portal gearing (something like 2:1 or 1.8:1) so it's only got half the stress on it as a regular axle. Yeah, I'm quite surprised that all of these "extreme" rockcrawlers stick with regular axles. You can't beat a portal-geared axle...or a planetary geared axle...for durability---or low gears!

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post #10 of (permalink) Old 12-06-2000, 04:41 PM
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Re: The Model 20. This may surprise a few of you!!

[img]/wwwthreads_images/icons/tongue.gif[/img] You guys are rubbing up against something that I have LONG thought would be the real answer to the lifted/low-geared/high-clearance Jeep. A SET OF OFFSET PORTAL GEAR AXLE ATTACHMENTS. You could connect to the ends of the normal axles. With planetaries you don't have to dump the differential upside down but with spur gears you would or else the Jeep would have a lot of gears backwards and few forward. By taking the reduction at the HUB, the RPM of all of the driveline components stays high and the torque that it has to transmit is reduced. Plus, if the brakes are inboard, they too have added mechanical advantage. By using the geared hub system, the Hummer uses a lightweight transfer case (242) and lightweight transmission in a heavy vehicle.[img]/wwwthreads_images/icons/crazy.gif[/img]

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