Rear end cases?

[sublimegtx]

Could someone explain the rear end cases to me. The differences between 489, 741, 742's. and can you tell what you have by looking. Are they or parts interchangeable? I'm not sure what I have. It is an 8 3/4 with 4.10s and I'd like to change to like 3.55s so I can make it more highway friendly. Thanks :3gears:

 

[MoparBill]

Those are the last 3 digits of the part #...should be big numbers on the side of your center section, can"t miss 'em!

 

[super-bee_ski]

Rear End Info:
Here is some data for you on the 8 3/4"
I recently bought a "741" for my 63 Max Wedge Clone Polara. Was originally told it was inherrently a WEAK rear-end due to the smaller pinion BUT this came off a Max Wedge car in 63' and some guys swear they are strong. The 741 have a taperd shaft. Also, the axlel shaft nut is visible on the rear hub.
The 742s and489s are slightly larger in the pinion and considered the better of the three #1: 489 #2: 742 and finally #3: 741

8-3/4"
1820657 (small pinion shaft, up to 1964)
2070741 (small pinion shaft, 1963 to about 1972)
2070742 (large pinion shaft, 1957 to 1968)
2881489 (tapered pinion shaft, 1969 to about 1974)

The 8 -3/4" was on hemi automatic cars. That is how much Mother MOPAR thought of them.

"Hope this helps a llittle"
"Super-bee_ski"

 

[jag_mopar]

don't forget 489 has a cone type sure grip design, 742 has a clutch type and 741 has cone. some prefer clutch over cone.

 

[Dako]

All you ever wanted to know about the 8 3/4...and then some.

http://www.mymopar.com/index.php?pid=62

The short of it:
741 -lightest weight...some will say good up to about 400hp
742 -heavier duty...eventually phased out
489 -heavier duty...it's what phased out the 742

 

[super-bee_ski]

Thanks Dako,
Yeah, the size of the pinion on the 741 carrier is: 1-3/8" NOTE: Used on Max Wedge Monsters so they have to be strong.
The 742 has a 1-3/4" pinion. Larger=stronger
The 489 carrier has the 1 7/8" pinion (I think) Again, larger=stronger.
Sublimegtx, you would be correct to go your original equipment 489 carrier and replace the 4:10 center section w/ a 3:55 OR 3:23. POSI UNIT.

 

[Dako]

Careful, super-bee_ski...some folks on this site take offense to the term, 'POSI UNIT'.

They prefer Ma Mopar's verbiage of 'Sure Grip'. :sideways tongue:

Wouldn't want someone accusing you of being a GM (Government Motors) fan...:argue:

Cheers.

 

[sublimegtx]

Ahha, ok got it. Great link there Dako, all I ever want to know and more! Now I just have to get under it and see what I have so I can price up some gears. It has 4.10 richmonds in a "Sure grip"

 

[super-bee_ski]

Damn C_ _ VY/GM lingo....!
I swear the GM guys are sending microwave modulated data to our homes at night when we sleep to brain-wash us!
Starting tonight I'm wearing an aluminum foil hat when I go to bed.

 

[Cranky]

Rear End Info:
Here is some data for you on the 8 3/4"
I recently bought a "741" for my 63 Max Wedge Clone Polara. Was originally told it was inherrently a WEAK rear-end due to the smaller pinion BUT this came off a Max Wedge car in 63' and some guys swear they are strong. The 741 have a taperd shaft. Also, the axlel shaft nut is visible on the rear hub.
The 742s and489s are slightly larger in the pinion and considered the better of the three #1: 489 #2: 742 and finally #3: 741

8-3/4"
1820657 (small pinion shaft, up to 1964)
2070741 (small pinion shaft, 1963 to about 1972)
2070742 (large pinion shaft, 1957 to 1968)
2881489 (tapered pinion shaft, 1969 to about 1974)

The 8 -3/4" was on hemi automatic cars. That is how much Mother MOPAR thought of them.

"Hope this helps a llittle"
"Super-bee_ski"

And how many have broke the 741 unit?

don't forget 489 has a cone type sure grip design, 742 has a clutch type and 741 has cone. some prefer clutch over cone.

These days, it's no telling what's what with all the swaps that's taken place over the last 20 years or so.....

All you ever wanted to know about the 8 3/4...and then some.

http://www.mymopar.com/index.php?pid=62

The short of it:
741 -lightest weight...some will say good up to about 400hp
742 -heavier duty...eventually phased out
489 -heavier duty...it's what phased out the 742

I'll take the 42 over the 89 any day just because of the crush sleeve crap....but, a solid sleeve can be installed inthe 89 too. Got to know what you're doing is all....

 

[super-bee_ski]

I'll let you know when my 741 breaks...Ha Ha!
Yup, as Budniks says: "Fill your library before you fill your garage"
Well, I didnt! I bought the 741 for $500 complete from Hub to Hub beleiving it was RARE and valuable.
Hell: a 74 Vega station wagon with yellow paint is probably RARE these days...dosent mean it's worth anything!
Oh well...the 63 Max isnt running yet but as soon as it's running, we can ALL take a poll on how many days/weeks..hours?.. before it explodes! (Implodes?)
"Super-bee_ski"

:iamwithstupid:

 

[65 Plymouth Satellite 426]

My '65 Automatic Had A 741 In It And I Wiped The Bearings Out Of It! Now Have The 742 Case...So Far No Problems! Anyone Need Just The 741 Case For Parts?

 

[Cranky]

My '65 Automatic Had A 741 In It And I Wiped The Bearings Out Of It! Now Have The 742 Case...So Far No Problems! Anyone Need Just The 741 Case For Parts?

I doubt the bearings wiped because it's a 41. When I was building rear ends a lot, I would always sell the 89's because that's what everyone wanted. NO ONE wanted anything to do with a 41 and I know why. Some dad gum magazine wrote an article about how good the 89 is and how much stronger it was over the others. Crap, I've had way more 89's come in for repairs than anything else! Anyways, I kept the 41's and 42's for myself and beat the crap out of them and never had any problems at the drag strip with any of them....and....there's no damn crush sleeve in them to mess up! If the shipping wasn't expensive, I'd take that 41 off yer hands. What all is left in it?

 

[65 Plymouth Satellite 426]

Entire Third Member...741 Case...2.76 Gears...All Internals

 

[Meep-Meep]

As mentioned the 741 is a 1-3/8" straight pinion, the 42 is a 1-3/4" pinion and the 89 is a 1-7/8" tapered pinion. The old DC book says the 489 is the strongest followed closely by the 742. And I will agree the 741 isn't exactly the worst rear end out there. It does have smaller bearings than the 742 and I seem to recall the 742 gears will not fit into the 741 case. I'm with Cranky on favoring the shims as opposed to the crush sleeve preload method.

 

[shag766]

this is all new and Greek to me, but, interesting, very interesting.:eusa_think:

 

[sublimegtx]

Had a chance to get under it over the weekend. It has the 489. When I change the 4.10s to 3.55s will it have an affect on driveability due to my converter stall speed? It has a 3500 stall, eventually I'd like to get a lower one.

 

[Cranky]

Entire Third Member...741 Case...2.76 Gears...All Internals

Shipping would be the killer....you're talking about 80 lbs on it....

As mentioned the 741 is a 1-3/8" straight pinion, the 42 is a 1-3/4" pinion and the 89 is a 1-7/8" tapered pinion. The old DC book says the 489 is the strongest followed closely by the 742. And I will agree the 741 isn't exactly the worst rear end out there. It does have smaller bearings than the 742 and I seem to recall the 742 gears will not fit into the 741 case. I'm with Cranky on favoring the shims as opposed to the crush sleeve preload method.

The engineers figured that a tapered pinion would have less deflection and it probably does but I've shaved ring gear teeth off of just as many 89's as the others. And if you plan on racing using the 89, the crush sleeve should go into the trash. It's kinda funny that they made a tapered pinion for the 8 3/4 and the Dana 60 never got one. Ever compare A 60's pinion with the 8 3/4's? It's pretty amazing that it's smaller than the one in a 42 case....so what were the engineers really thinking? :toothy5:

Had a chance to get under it over the weekend. It has the 489. When I change the 4.10s to 3.55s will it have an affect on driveability due to my converter stall speed? It has a 3500 stall, eventually I'd like to get a lower one.

You will notice a difference with the way it acts especially at slow speeds....a trans cooler might be a good idea if you do drive it slow a lot because the converter will most likely be slipping more often than before. 3.55's are more of a street performance gear ratio while a 3500 stall is more of a mild track performance unit imo.

 

[super-bee_ski]

Well,
That IS good news for me. As I mentioned earlier in this thread, I WAS told the 741 handled the MAX WEDGE demands. Some are still around (mine included). But: there are X-perts out there that told me the 741 will blow up.
I dont know, but I have a hunch that the 741 isnt as bad as people think.
As Meep Meep and Cranky seem to know quite a bit more than the average "joe".
Anyway, sublimegtx: "keep us posted"

 

[Cranky]

I started learning about rear ends in the early 80's when a buddy was getting a bit serious with a 69 4 speed Road Runner and since I didn't have anything to run at the time, I helped him. Also, there wasn't many shops around that did ring and pinion work during that time....at least not any that didn't cost you your first born. Anyways, the thing started shaving ring gear teeth when it got into the low 11's so the car went on a diet. Now running high 10's after adding more power too, it broke it's 3rd ring gear so a Dana went in and no more breakage and the car was well into the 10.60 range. Having a good clutch is important too and NEVER side step any clutch unless you like breaking things in a hurry. I know many do it but there's no real advantage to doing that. It's also important to have the right pinion angle too. The wrong angles are not just hard on u-joints. Anyways, he bought a pinion dept setting tool (I still use it today) and we went at it. It was the blind leading the blind. Remember, no one had the internet back then lol. Our first set of gears turned out good.