how to identify 742 or 489 aluminum case for rear end

Posted By: 440dustr

how to identify 742 or 489 aluminum case for rear end - 07/02/12 06:27 PM

I have had an aluminum case for my mopar 8-3/4 rear. I thought it was a 489 case but how do I know for sure. I bought richmond gears 3.55 and eaton detroit truetrac with new richmond bearing kit all for a 489. but it looks like the front pinion gear bearing is to small that came with the kit.
the aluminum center section has no numbers on it to go by.
if I have all 489 stuff I assume it wont fit a 742 case is that correct?

thanks

Posted By: JohnRR

Re: how to identify 742 or 489 aluminum case for rear end - 07/02/12 07:05 PM

The MP alum case was only ever made for 742 gears .

Posted By: 440dustr

Re: how to identify 742 or 489 aluminum case for rear end - 07/03/12 03:57 PM

who else makes an aluminum case besides MP
the one I have doesnt have the bolts go through the houseing just the 2 bolt on the end caps like a normal carrier.

Ill have to go take a picture of mine maybe someone has seen this before.

Posted By: copchaser

Re: how to identify 742 or 489 aluminum case for rear end - 07/03/12 04:03 PM

Mickey Thomson made them years ago also, I'm thinking there were 742 also.

Posted By: dogdays

Re: how to identify 742 or 489 aluminum case for rear end - 07/03/12 04:06 PM

That part belongs in the Smithsonian!
R.

Posted By: JohnRR

Re: how to identify 742 or 489 aluminum case for rear end - 07/03/12 04:46 PM

I didn't know anyone else made one , is it aluminum or magnesium ?

Posted By: 446acuda

Re: how to identify 742 or 489 aluminum case for rear end - 07/03/12 06:29 PM

E-berg had a magnesium M/T case in the Green Brick for a while.

Posted By: 440dustr

Re: how to identify 742 or 489 aluminum case for rear end - 07/23/12 05:53 PM

I just got my centersection back I was told the aluminum houseing was made by stange and that the bearing I needed was used with a ford 9" heavy duty. Ill post of picture of the center section soon

Posted By: jcc

Re: how to identify 742 or 489 aluminum case for rear end - 07/24/12 03:56 PM

Quote:

who else makes an aluminum case besides MP

This I believe is a Mark Williams Alum 8.75, along side a MP, might want to notice the thickness of the MW mounting flange, it is stout, and not for sale.

Attached picture 7305687-IMG_6124-Alum-Housings-web.jpg

Attached picture 7305687-IMG_6124-Alum-Housings-web.jpg

Posted By: 52savoy

Re: how to identify 742 or 489 aluminum case for rear end - 07/24/12 05:33 PM

There was time(1960s-early '70's) when a lot of dragsters used 8 3/4's and cases were made out of different materials.. I would guess they were all 742 cases because the pinion isn't tapered, which is the weak link of a 489.

Posted By: Supercuda

Re: how to identify 742 or 489 aluminum case for rear end - 07/24/12 06:52 PM

Quote:

There was time(1960s-early '70's) when a lot of dragsters used 8 3/4's and cases were made out of different materials.. I would guess they were all 742 cases because the pinion isn't tapered, which is the weak link of a 489.

The weak link isn't the taper so much as it is the crush sleeve that can get loose with repeated hard usage. A solid shim replacement setup will cure that.

Posted By: CUDA8U

Re: how to identify 742 or 489 aluminum case for rear end - 07/24/12 07:07 PM

what's all involved in installing the "crush sleeve" elliminator kit?

shouldn't all cases be stamped or numbered?

Posted By: 52savoy

Re: how to identify 742 or 489 aluminum case for rear end - 07/24/12 11:26 PM

Quote:

Quote:

There was time(1960s-early '70's) when a lot of dragsters used 8 3/4's and cases were made out of different materials.. I would guess they were all 742 cases because the pinion isn't tapered, which is the weak link of a 489.

The weak link isn't the taper so much as it is the crush sleeve that can get loose with repeated hard usage. A solid shim replacement setup will cure that.

I'll stick by my comment unless someone can prove me wrong..
The spacer is one of two weak links on a 489,not counting ring gear diameter or deflection. 742's have(or used to) a much larger gear choice because of their strength(pin.stem diameter). Chrysler's "Performance Parts" pro gears were for a 742 case for a reason.

your turn..

Posted By: DoctorDiff

Re: how to identify 742 or 489 aluminum case for rear end - 07/25/12 03:14 AM

Why would a tapered pinion be weaker than a big step in the pinon? Both designs neck down to the same OD in the front.

Here are side by side pictures:

http://www.moparts.org/Tech/Archive/axle/1.html

Posted By: Supercuda

Re: how to identify 742 or 489 aluminum case for rear end - 07/25/12 03:39 AM

Quote:

Quote:

Quote:

There was time(1960s-early '70's) when a lot of dragsters used 8 3/4's and cases were made out of different materials.. I would guess they were all 742 cases because the pinion isn't tapered, which is the weak link of a 489.

The weak link isn't the taper so much as it is the crush sleeve that can get loose with repeated hard usage. A solid shim replacement setup will cure that.

I'll stick by my comment unless someone can prove me wrong..
The spacer is one of two weak links on a 489,not counting ring gear diameter or deflection. 742's have(or used to) a much larger gear choice because of their strength(pin.stem diameter). Chrysler's "Performance Parts" pro gears were for a 742 case for a reason.

your turn..

What?

The 489's pinion is thicker than the 742's in most of it's length and the same in the rest. Therefore, by your reasoning the 489 should be stronger.

You can believe whatever you want doesn't make it right.

Posted By: 52savoy

Re: how to identify 742 or 489 aluminum case for rear end - 07/25/12 09:18 AM

What ????

Removing metal doesn't make the stem stronger unless you've found out about some Area51 process that defies logic and.....metal..

The pinion is called "tapered for a reason. At just one point(1 7/8") is it bigger than a 742(1 3/4"). A 742 is straight cut to the yoke, just slightly smaller dia. than a 489 and therefore stronger. Now if Chrysler in hindsight decided to make the 1 7/8" machined straight all way over to the yoke we would have something.
Anyone can believe what they want but facts ARE FACTS.

Been doing this mopar thing going on 50 years so I don't need to make it up... and I doubt under any circumstances that I could convince you but no problem. If you make it my way some time I'll start up the grille and we'll go my shop to sort it out

while the Texas BBQ is smoking..

comparison shot..... web page

I remember in the 70s Chrysler started getting negative feedback from racers who were breaking the large stem pinions in half. They put out bulletins on that subject and recommended racers use the non-tapered 742 case. The story is in the mopar bible. I happened to have worked for local stock and super/stock racers Starkey and Christian and their expierience went back to 1959. Even though I knew of Chrysler's position, it was the first time I got it from racers but with more details...

but it's ok... do your own thing or go Dana.

Attached picture 7306904-lastofthelonghairandpinionsizes005.jpg

Attached picture 7306904-lastofthelonghairandpinionsizes005.jpg

Posted By: jcc

Re: how to identify 742 or 489 aluminum case for rear end - 07/25/12 01:56 PM

Regarding strength of 742 vs 489 stem, if someone could PROVE to me that it fails more then say once in a million, I'll join the argument of arraigning the deck chairs on the Titanic.

My suggestion, argue something more worthy.

Posted By: DoctorDiff

Re: how to identify 742 or 489 aluminum case for rear end - 07/25/12 02:12 PM

I agree. Both designs have a square "stress riser" just inboard of the front bearing journal. The pinion diameter is overkill anyway. The weak link is ring gear size.