Re: Axle and gear ratio interchange confusion

[TABunsey@xxxxxxx]

Marty:

There is no error in your logic. 2.87 gears WILL fit anyplace that a 3.54 gear will fit. The eBay vendors are UNINFORMED and INCORRECT.

There is no difference (at least with Stock AMC gears). AMC ONLY MADE ONE CARRIER ASSEMBLY FOR THE MODEL 20 REAR AXLE (Well, actually there are two carriers--a "Twin Grip" carrier and an "Open" carrier).

LOOK IN THE AMC PARTS BOOK. ONLY ONE PART NUMBER!!!!!!

The aftermarket idiots keep saying that there is a "break" around 3.07 ratio, or so.

IT AIN'T SO (AT LEAST AMC DOESN'T THINK SO). 
I have pulled 3.54 gears and replaced them with 2.87 gears IN THE SAME HOUSING, SAME CARRIER. 

IT BOLTED TOGETHER AND WORKED FINE. FOR YEARS!!! Behind a 401.

Alright, alright. 
Yes, AMC DID use a different carrier for the Concord/Pacer V8 cars with the 2.56 ratio. But this only applies to 1978-79 model year cars with an automatic and no "Twin Grip".

I have such a ratio I took from a V8 Pacer. I installed it in a V8 Rambler American rear axle. Works fine, too. Bolts right in as an assembly.

The AMC 6-cylinder rear end DOES require one of two carriers, and the change IS around 3.08. It looks as if the taller ratios have a pinnion gear with such a large diameter that the mounting flange on the carrier had to be moved outboard to keep proper gear mesh.

If I sound "touchy" about this, it's because I am. Every couple of months the same issue raises it's ugly head. Then it gets talked to death & resolved. Then a few months go bye, and the issue comes up again.  

Arghhhh!!!!!

Boy, it would be nice if the list would permit "bold face", "underlines" and "italics" to emphasize various points. But since it doesn't, I need to use CAPS instead.

Tom Bunsey

My "bible" is the AMC Parts Books. After all, AMC built the cars, Not some aftermarket guys who think if it works that way on "Chebbys", it must work that way on everything else.




On January 14, 2005 Marty Bricker wrote:

> I need a 3.54 rear end to take advantage of the cam I
> want to use in a 401 buildup I'm doing.  There are a
> couple of sets listed on Ebay but they say they will
> not fit a rear end with 2.87 gears.  I broke out my 74
> TSM and I'm really confused now.  Under 'Axle and
> Propeller Shaft' it lists the 2.87 ratio rear end as
> having the same size gear (8-7/8") as the 3.15 and
> 3.54.  In the 'axle ratio availability' chart for a
> 304 engine (original one in my Jav/AMX) with a 998
> tranny it lists the 2.87 as standard and the 3.15 as
> optional with a 8-7/8 axle.  It also lists the 3.15 as
> standard and the 3.54 as optional with the same tranny
> and axle for the Matador and Ambassador. All of the
> listings for a 3.15 as standard have the 3.54 as
> optional and all are with the same 8-7/8 axle.  To me,
> it would follow that if a 3.15 is optional and will
> replace a 2.87 and a 3.54 is optional and will replace
> a 3.15 then a
> 3.54 will also replace a 2.87.  Someone please explain
> the error of my logic...ie,what is the difference?
> Thanks.
> Marty
> 
> 
> 
> 
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