Any advantages for having a 741 differential case versus a 742 case?

[lacrebob]

I have a 741 case. I'm wondering why the 741 would continue to be used along with the 742 case when the 742 case is stronger? The two cases don't seem to be different enough to make a materially difference in cost. Could the 741 have an advantage over the 742 such as having lower friction?

 

[benno440]

741 case ended in 68 and was the light duty case in small block cars 742 case superceded it and was built stronger (i have heard, dont know in which way though, google it) used in big blocks.
not sure what much was different in them. i dont think the 741 case ever had a sure grip though

 

[daredevil]

Yep.usually cheaper, and stronger than their rep.

 

[RustyRatRod]

There's almost no measureable difference in strength. The 741 can be beat to death. I've been messin with Mopars a little over 30 years now and the only broken pinions I've ever seen were 489 cases where the pinion nut backed off because the crush sleeve failed.

 

[Meep-Meep]

The 741 has smaller pinion bearings than the 742. Other than that they are very similar in construction. 741's are usually cheaper because everyone knows they are not 742's or 489's. The MoPar performance manual will say the strongest is the 489 followed by the 742 but make no mention about the potential crush sleeve failure of the 489 (that I recall anyway). The shaft is stronger on the 489 and 742 because it's larger, but if you don't break a 741 then what difference does it make? Ever see the pinion shaft and bearings on a 9" Ford? Smaller than a 741. But they do have that pinion support bearing so that accounts for something.

 

[moparmarks]

My 65 Satellite 383 4-spd and a 65 Belve 361 4-dr I had both have 741 Suregrips.

 

[Cranky]

Gear ratios (aftermarket) were limited for the 741 but don't know if that's still the case. I'll take a 42 as my first choice then it's a toss up between the other two but I'd rather set up the 41 vs the 89....unless that damn crush sleeve goes in the trash and use a solid spacer.

 

[super-bee_ski]

The 741s were "stout" enough to be put on the Max Wedge cars.
I have a 741 form a 63 Plymouth Maxie. 3:91 ratio.
It IS going in my 63 Dodge Max Wedge clone.

 

[furyus63]

lacrebob,

I think the 741 case is capable of any job short of all out drag racing. The only real difference is the size of the pinion shaft both using 10-spine. The 741 uses a 1 3/8" pinion shaft and the 742 uses a 1 3/4" pinion shaft, which is about the "only advantage". The 741 case was used in production until 1974. The 742 was used in production until 1969.

My 1963 Fury Poly stroker 400hp with 285-70R-15 tires runs a 742 case 3:55 Sure Grip rear
My 1963 Sport Fury Max Wedge 400+hp with 285-70R-15 tires runs a 741 case 3:91 Sure Grip rear

Nick Tiberio
FuryUs63

 

[lacrebob]

Thanks for the replies gentlemen. I don't yet know how much horsepower the engige will ultimately have, and I want to spend money wisely, and just once. The 742 seems like an upgraded 741 so it seems like the 741 would have been phased-out a lot sooner than it was without some kind of advantage. I suppose there could have been a very small cost advantage and it was deemed that the 741s were strong enough such that there wasn't any reason to spend a penny more on putting a 742 in a new car.

 

[Cranky]

Gear ratios (aftermarket) were limited for the 741 but don't know if that's still the case. I'll take a 42 as my first choice then it's a toss up between the other two but I'd rather set up the 41 vs the 89....unless that damn crush sleeve goes in the trash and use a solid spacer.

@Denham What is it that you disagree with on that post?

 

[Cranky]

lacrebob,

I think the 741 case is capable of any job short of all out drag racing. The only real difference is the size of the pinion shaft both using 10-spine. The 741 uses a 1 3/8" pinion shaft and the 742 uses a 1 3/4" pinion shaft, which is about the "only advantage". The 741 case was used in production until 1974. The 742 was used in production until 1969.

My 1963 Fury Poly stroker 400hp with 285-70R-15 tires runs a 742 case 3:55 Sure Grip rear
My 1963 Sport Fury Max Wedge 400+hp with 285-70R-15 tires runs a 741 case 3:91 Sure Grip rear

Nick Tiberio
FuryUs63

8 3/4's do struggle in the higher horsepower cars and especially so behind a stick. The lighter the car they are in the better but that's with many rear ends. I would love to get my hands on a S60 because they have the carrier bearing adjusters for setting back lash. Setting back lash with shims sucks in my book lol

 

[moparmarks]

Cranky Ol' bean, you do know that this thread is over 12 years old, right?

 

[Cranky]

Cranky Ol' bean, you do know that this thread is over 12 years old, right?

Yup but someone else woke it up by giving me the red X so someone is reading through this stuff

 

[moparmarks]

Ooooooooooooooh.

 

[Cranky]

Ooooooooooooooh.

And it doesn't hurt anything to revive some of the old stuff.....

 

[moparmarks]

I'm old and love being revived.

 

[Cranky]

I'm old and love being revived.

 

[440 PHIXX]

I pulled the center section out of a ‘68 Imperial I had back in the 80’s before I gave it to the junk man. I knew it was a Sure Grip, but was bummed to recently see 742 on it and not 489. Oh well.

 

[Cranky]

I pulled the center section out of a ‘68 Imperial I had back in the 80’s before I gave it to the junk man. I knew it was a Sure Grip, but was bummed to recently see 742 on it and not 489. Oh well.

Bummed to see a 742? No crush sleeve in those.....and they have a good selection of gears to choose from.