Can anyone ID this?

I have no clue and would appreciate the help.

 

Center Section Types
The 8-3/4" axle was available in three basic types. The types are differentiated by the pinion stem diameter....1-3/8", 1-3/4", 1-7/8". The choice of axle pinion assembly was determined based on the application. Differential bearing setting (ie. backlash ) is set with threaded adjusters on all carriers. All 8-3/4" carrier assemblies can be identified externally by the casting numbers.
1-3/8" small stem pinion (aka. '741')
Carrier casting numbers: 1820657 (1957-1964), 2070741 (1964-1972).
This assembly was typically used in low weight/low horsepower applications through low weight/medium horsepower and high weight/low horsepower applications.
Pinion depth and bearing preload is set with shims.
1-3/4" large stem pinion (aka. '742')
Carrier casting numbers: 1634985 (1957-1964), 2070742 (~1961-1969).
This assembly was replaced by a phase-in of the 1-7/8" pinion starting in the 1969 model year. 1970 RW (Plymouth and Dodge mid-size) were the last models to use the 1-3/4" which appeared in a 2881489 case. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications.
Pinion depth and bearing preload is set with shims.
1-7/8" tapered stem pinion (aka. '489')
Carrier casting numbers: 2881488, 2881489 (1969-1974).
This assembly was introduced in 1969 and was phased-in to relace the 1-3/4" unit through 1970. Note: the 1-3/4" pinion also appeared in some '489' carriers during this period. By 1973, the '489' was the only unit available in passenger car applications. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications.
Pinion depth is set with shims, preload is set with a crush sleeve.
The '741' commonly has a large X cast on the left side, the '742' may have a large 2 cast on the left side, and the '489' has a large 9 cast on the left side. Through 1965, the factory ratio was stamped on the identification boss, followed by an 'S' if Sure Grip equipped. After 1965, a tag was affixed under one of the carrier mounting nuts to identify the ratio. If Sure Grip equipped, an additional Sure Grip lube tag was sometimes affixed; later years sometimes had the filler plug painted orange.
Gear ratios available on the 8-3/4" axle through the years include: 2.76, 2.93, 3.23, 3.31, 3.55, 3.73, 3.91, 4.10, 4.56, 4.89, 5.17, 5.57. On OEM gear sets, the ratio is usually stamped on the ring gear edge. Ratio may be determined by the number of teeth on the ring gear divided by the number of teeth on the pinion gear or by counting the ratio of the number of turns of the pinion relative to one turn of the axle shaft. The 8-3/4" center section is removed from the front of the housing. To remove the center section, remove the wheels, brake drums, and drive shaft (note: pre- 65 units have a pressed-on brake hub...requires a puller for removal). Remove the axle shafts, 5 bolts on the backing plate flange on post 64 units, use puller for pressed-in pre-65 units. Remove the 10 nuts on the housing studs around the carrier perimeter. Remove the carrier...may require prying, fluid will drain when carrier gasket seal is broken.

 

Looks like I'll be shoppig sometime in the future for a replacement.

Would like a 2070742 with a 3.23 to 3.73 ratio.

Do you know approximately what this 2070741 would be worth with 2.73 gears?

 

The case in your picture is a 741, id go with a 489 myself..

The ratio will be on the 3rd member if you pull it out.

Or if you turn the wheels 1 full turn and watch the pinion turn you'll also get the ratio.

 

OK - here is the little knowledge I have acquired. Of the three, 741's are less sought after. If it has a sure-grip, I would put the max price at $275 -350 without, $50 -100. I am assuming this is in great condition? Also, the yolk/u-joint is probably the small one, so on the low side of the numbers. If it is a bigger one higher. And this is the assumption buyers are in need and supply is low in your selling area.

and I agree with Blue - find a 489 case -there are more options available with it and is the strongest of the group.
Good luck

 

Alright, had my son spin the drive shaft to see how many turns it took to get 1 full wheel turn.

We did it three times to double check. The drive shaft takes less than 2 1/4 turns to make one full rev, but I've not seen or heard of a 2.23 gear ratio.

What are we missing or is it possible?

 

Were both wheels turning or just one? You only want one wheel turning when you do this. Is there a tag anywhere on the mounting bolts? Other thing you could do is drain the diff, disconnect the driveshaft and pull the center section out. The ring and pinion teeth count should be on the ring gear or you can count the ring gear teeth and divide it by the amount of teeth on the pinion.

 

Only one wheel was turning. Looks like for true ID I will need to pull the PIG, as there are no tags on the rearend.

 

Just curious, did you mark the driveshaft with chalk and use that as a reference point? I am only wondering, because a 2.23 ratio seems extremely weird; I think the highest was 2.75.

 

Spin the wheel and count the driveshaft revolutions, not the other way. Mark the yoke and diff with chalk or crayon for a reference point, you will have either a 2.76 or 3.23 gear set. Those were the most common in the 8.75 w/o suregrip.

 

Juast used the universal joint for a reference point, but we spun the driveshaft to get one full turn on the wheel. I read that this really was not a good way to do this with a LTD slip.

I will be dropping the rearend in order to clean the undercoating off. When I do that, I'll pull the pig and look at the gears. Thanks for all the help! This is my frst project and appreciate all the assistance. I'm learning alot from all of you!

 

It works best if you spin the wheel one full turn and count the driveshaft revolutions.

 

If it is limited slip or posi, both wheels will spin in the same direction anyways. If it is an open carrier, one wheel will spin backwards, so someone will have to hold that wheel while someone turns the other one.

 

My 1973 Challenger has a 8-3/4 rear end. The numbers cast into the housing are 2881489, and then there is a 1053. Is the 1053 the date code? If so, how do you interpret that? 105th day of 1973?

Thanks for any help I can get.

 

I don't think a 489 came in a 1973 car