8 3/4 3rd member question?

[J-Rat]

Kinda new here and had a question about the third members. I know mopar offers the 741, 742 and 489. My question is are they all interchangeable with the 8 3/4 rear end, and if so dose it require modifying the driveshaft? Thanks, J-rat.

 

[fishy68]

The entire units are all directly interchangeable without any modifications at all. There are differences within the different units themselves (bearings, gears, carrier).

 

[fishy68]

Oh yeah, good to see a local. We hit the Alton/Edwardsville/G. City area cruises as much as possible.

 

[demon seed]

Kinda new here and had a question about the third members. I know mopar offers the 741, 742 and 489. My question is are they all interchangeable with the 8 3/4 rear end, and if so dose it require modifying the driveshaft? Thanks, J-rat.

They're interchangeable with the rear housing and no the same drive shaft can be used for all three. Here's some lite reading.
http://www.moparts.org/Tech/Archive/axle/1.html

 

[J-Rat]

Thanks guys for the info. I bought a rear end off my old man, and I was just going to swap the third members out and neither one of us was sure if it would would work out.

And to fishy68 when do the cursies all go on would like to get out to one of those this year.

 

[cudamark]

The entire units are all directly interchangeable without any modifications at all. There are differences within the different units themselves (bearings, gears, carrier).

That's not 100% true. The '64 and older 3rd members use a different thrust block in the middle and different length axle shafts between sure grip and non-sure grip, to match. There are also several different u-joint sizes and spline counts so swapping them isn't always a simple swap.

 

[fishy68]

That's not 100% true. The '64 and older 3rd members use a different thrust block in the middle and different length axle shafts between sure grip and non-sure grip, to match. There are also several different u-joint sizes and spline counts so swapping them isn't always a simple swap.

That's true but he didn't mention them. He only mentioned the 741, 742, and 489 carriers which were made later. That's why I said they'd directly interchange. Your right about the yoke/u-joint sizes. I forgot to mention that.

 

[fishy68]

And to fishy68 when do the cursies all go on would like to get out to one of those this year.

From spring to fall. Here's a link to the Lakers car club cruises

http://clubs.hemmings.com/clubsites/lakerscarclub/

Looks like their starting pretty early this year. Not sure I'd want to do a cruise the first week of march. BURRRR.....

Anytime you go to one you'll get several flyers handed to you inviting you to other cruises also.

 

[cudamark]

That's true but he didn't mention them. He only mentioned the 741, 742, and 489 carriers which were made later. That's why I said they'd directly interchange. Your right about the yoke/u-joint sizes. I forgot to mention that.

The 741 and 742 3rd members were started before '65 so they were also used with axle nut rears. Those early axles used shims to set the axle end play instead of the adjustable bearing retainer. Those early axles were an 1/8" different in length depending if they had a sure grip or not. The later 3rd members used the same thickness thrust block setup so you could use the same length axles. Some of the early ones may be a bolt-in with the later axles but some won't work because you can't get the end play set correctly. You would either have to change the axle shaft length or change/modify the thrust block assy.

 

[fishy68]

The 741 and 742 3rd members were started before '65 so they were also used with axle nut rears. Those early axles used shims to set the axle end play instead of the adjustable bearing retainer. Those early axles were an 1/8" different in length depending if they had a sure grip or not. The later 3rd members used the same thickness thrust block setup so you could use the same length axles. Some of the early ones may be a bolt-in with the later axles but some won't work because you can't get the end play set correctly. You would either have to change the axle shaft length or change/modify the thrust block assy.

Your right Mark. My mistake. I was thinking I read that before 65 there were just the 657 and 985(?) centers. That's what I get for trusting my memory.:banghead:

 

[cudamark]

Your right Mark. My mistake. I was thinking I read that before 65 there were just the 657 and 985(?) centers. That's what I get for trusting my memory.:banghead:

You too? It used to be my best friend......now it fights with me every day!