AMC Model 20 rear end parts swap discussion part 99

[Guynn <amx69@xxxxxxxxxx>]

If you already ''know it all;''  on Model 20 rear ends,then don't bother 
reading this as you could not possibly learn anything from it. If you 
are teachable you might just learn why there is so much confusion over 
model 20 gear/carrier swaps.

I tried to post earlier but I was too long winded and it was too big to 
make the board. So, I will condense it a lot. I replied on Jim Bs 
comments, so he got the big post but not the site.

Tom Bunsey, you are right. But also the Aftermarket is right Where the 
problem comes from is Factory parts and Aftermarket parts. Just because 
a certain gar ratio in Factory gears fits in Factory carriers does not 
mean that every aftermarket gear, or carrier will affect the same swaps.

You have to understand that the aftermarket carriers that are advertised 
as 3.08 and up gears really do fit the gears advertised.Just because a 
gear ratio is say, 3.08 does not mean that every manufacturer arrives at 
the 3.08 in the same way.

Example a 3.08 AMC Factory gear is a 13/40 count but a Precision 
aftermarket 3.08 gear is 14/43 count.

One thing that is 100% constant in all rear end applications is that the 
Pinion gear is always located in the exact same place in the housing. 
So, with that in mind, you can easily see that when the number of teeth 
on a Pinion gear increases, the gear gets bigger in diameter. Since the 
centerline of the pinion never changes, then it stands to reason that 
the Ring gear gets Thinner as the Pinion gear gets bigger. The reason 
there is more than one carrier is because they moved the Ring Gear 
Mounting Flange on the 2.73 and 2.56 model carriers because the pinion 
had grown so large that the ring gear was too thin for strength needed. 
So, they move the flange.and the ring gear can then gain more width and 
be strong enough to not easily break.

Get your hands on factory carriers, both posi, and open. Then get an 
Aftermarket carrier. Stand them on end, side by side, you will see the 
difference where the mounting flange is located reletive to each other. 
There are at least 5 Factory AMC carriers, maybe 6. You have 2 series & 
3 series Open carriers, and the same break for Posi carriers, and then 
Jeep has a Locker available. I am not sure if they ever made a Factory 2 
series Locker Carrier.Now go look at the giant list of Aftermarket 
carriers,If you start looking at parts and comparing them you will 
plainly see there are many different carriers with many different ring 
gear flange locations. All 3 series units do not have the exact location 
of the Flange. If they did, then there would be no reason to have this 
discussion/confusion over the Model 2o rear end .

The Aftermarket folks are not Idiots as has been suggested. The 
aftermarket guys know what THEY built and what will fit it. The 
Aftermarket is not saying that the Factory gears and carriers are 
exactly like what they make.  So just because you can install a Factory 
3.54 on a factory 2.87 carrier does not mean you can install an 
aftermarket 3.54 on a Factory 2.87 carrier.

Yes, many ratios change out with each other, but not all. And one 
manufacturer gives the carrier break as 2.73, that is for THEIR carrier, 
not the Factory piece. Same as when an aftermarket manufacturer states 
carrier break is a 3.07. They mean THEIR carrier, not the Factory unit, 
and not the other manufacturers unit.  Thiese are real true carrier 
breaks in the Aftermarket. Yukon carriers/gears break at 3.08, Precision 
Gears carrier/gear break comes at 2.76, Neither company is ''Idiots'', 
neither one is Wrong.

Tom, Sorry you are upset about the same questiuon coming up a lot. It 
comes up a lot because folks do not understand how there could be so 
many different answers to the same question. And, it will continue to 
come up as long as folks accuse others of being Idiots just because they 
don't understand that Aftermarket parts are not built exactly like 
Factory parts.

If you are one of the ''confused'' here, look into exactly what I have 
said, get the parts, compare them, you might just learn something you 
can pass on besides ''These Aftermarket Idiots Don't know ...............''
Factory carriers and Aftermarket carriers are not all built the same. 
And Factory AMC gearsets compared to Aftermarket gearsets are also not 
made the same way [designed I should say]  When we can accept that it 
becomes a lot easier to understand why so many different carrier breaks 
are listed.

If this is not plain enough please state what part you don't understand. 
As I said, I posted[or tried to]] a lot longer answer. It is really very 
easy to understand. All parts for AMC model 20 rear ends, carriers and 
gearsets are NOT created equal. [exactly alike] and so all gear/carrier 
swaps posible with Factory AMC rears is not the same as \the swaps 
available using aftermarket Carriers and /or gearsets. And... No one is 
an IDIOT because of it. Just the facts, the parts are different so the 
break points are also different.

I hope somebody, at least ONE lister can get this. If so, I only got 
another few thousand AMCers that have not gotten it , to get the message 
to.

Tom Bunsey, No swipe at you personally, it was you this time calling the 
aftermarket idiots. Others did so the last time the model 20 discussion 
came up. It seems this model 20 swap issue always causes the ''right'' 
folks to toss the Idiot banner out there.

Hope this one is not too long.

Regards,

Randy Guynn