How do identify which center section I have?

[pinkpanthr]

Looked through the older topics and haven't been able to get a clear answer, so can anyone tell me how to identify whether my center section is a 489 or a 742? Thanks in advance.

 

[generaljmwlee]

A number in a casting on the center, think it's the last three numbers on it.

 

[pinkpanthr]

Thanks. I'll take a look tomorrow.

 

[generaljmwlee]

Like this

 

[4spd69RR]

:yeathat:

 

[pinkpanthr]

What are the major differences between the two? I know it's hard to find anyone that will work on 489's but that's about all I know.

 

[moparmonk]

Really not a lot different except for the parts that go in them! I believe the 489 does not have replaceable clutches but I honestly can't confirm that.

 

[pinkpanthr]

I have a 742 case with a 3:55 open rear. The reason I asked is because I'd like to go to a sure grip rear with probably 3:23's. Just wanted to make sure there wasn't anything special I would have to look for.

 

[69hemibeep]

The 489 was thought to have the strongest pinion gear but that has been questioned as of late. They came with a cone style limited slip if equipped which can be tightened up with some machine work, the earlier ones had replaceable clutches. And the crush sleeve on the pinion can be replaced with a spacer now. I don't know where they came from, they are like mushrooms I have 3 -742s, 2-741s and 2-489s with different gear sets :basketcase:

 

[droptop]

....... I have 3 -742s, 2-741s and 2-489s with different gear sets :basketcase:

Hoarder. :acme:

 

[moparmonk]

The 489 was thought to have the strongest pinion gear but that has been questioned as of late. They came with a cone style limited slip if equipped which can be tightened up with some machine work, the earlier ones had replaceable clutches. And the crush sleeve on the pinion can be replaced with a spacer now. I don't know where they came from, they are like mushrooms I have 3 -742s, 2-741s and 2-489s with different gear sets :basketcase:

No wonder the rest of us can't find any rear ends. LOL! Do you have a different ratio for each of the carriers? Do you find it easier to change the whole axle or just the carrier. Is there a Sure-Grip available for a 741 case? Sorry for the questions but always have been curious on these issues

 

[69hemibeep]

No wonder the rest of us can't find any rear ends. LOL! Do you have a different ratio for each of the carriers? Do you find it easier to change the whole axle or just the carrier. Is there a Sure-Grip available for a 741 case? Sorry for the questions but always have been curious on these issues

Yes, the carrier, yes. LOL

 

[Big John]

casting #'s.

1 3/8" pinion stem:
657 1957-64
741 1964-72

1 3/4" pinion stem:
985 1957-64
742 1961-69
489 early 1969, but I've never seen one

1 7/8" tapered stem
489 1969-74

Two Sure grip units

Dana Power Loc (clutch plates): 1958-69
Borg Warner (tapered cones): 1969-74

The Dana is easy to rebuild and the Borg Warner is a lot harder, but there are people rebuilding them. They are interchangeable in any center section as long as you use the right bearings for the unit.

Don't figure on the sure grip unit corresponding with the casting number on the center section. Lot's of stuff gets swapped over the years.... and even if it's never been out of the car, you never know what was installed in that axle on any given day.

 

[Basketcase]

Hoarder. :acme:

:yeathat:

 

[ACME A12]

Don't figure on the sure grip unit corresponding with the casting number on the center section. Lot's of stuff gets swapped over the years.... and even if it's never been out of the car, you never know what was installed in that axle on any given day.

Yep. Mrs. ACME's '70 Swinger has a 742 with the cone SG unit.

 

[ACME A12]

Hoarder. :acme:

:lmao::lmao::lmao:

 

[69hemibeep]

:lmao::lmao::lmao:

:toetap: :toetap::toetap:

 

[69383RR]

I have a 742 case with a 3:55 open rear. The reason I asked is because I'd like to go to a sure grip rear with probably 3:23's. Just wanted to make sure there wasn't anything special I would have to look for.

I'm curious why you would want to downsize from the 3:55 to the 3:23's , most people on this sight and elsewhere all seem to want the higher gear ratios .
Also , you said you had an open rear . Is that the setup the car came with ?

 

[pinkpanthr]

I'm curious why you would want to downsize from the 3:55 to the 3:23's , most people on this sight and elsewhere all seem to want the higher gear ratios .
Also , you said you had an open rear . Is that the setup the car came with ?

The car came with open 3:55's. The reason I would downsize is that my car is a driver, I don't own a trailer or even a truck. My goal is to take her to Carlisle next year and that is an 1100 mile round trip of mostly interstate. And I want Sure grip just in case I decide to make a couple passes for fun.

 

[69383RR]

I too will be at Carlisle next year ,at least that's the goal anyway . We will deffanenly have to get together .
I took a look under the car yesterday to see what center section I have and it is a 742 but with the 2.32 gears and sure grip . I too am concerned about long haul highway driving but would like to have the capability for the occasional burnout . So I guess what I am asking is the 3:23 gears with sure grip capable of producing a decent burnout ?