Difference between 741 and 742?

[demon seed]

I've been trying to get a new set of 3:91's but can't find them.

If you're saying 3.91's for a 741 case then yes new 741 gear sets are getting rare, I'm not sure anyone makes them anymore just 742 and 489. Have you talked to Dr. Diff?

http://www.doctordiff.com/

 

[crackedback]

You can put any 8.75 RING gear in any 8.75 case, they are all the same for a specific ratio.

How would you put a 489 or 742 pinion in a 741 case when the OD of the tapered cup for each is .5" difference? The 489/742 OD is 3.5", 741 has a 3" OD. Maybe if there was some sort of special ring to put that bearing in the 741 case. The 489/742 bearing is too large to fit in the 741 cup bore itself, IIRC.

Look at the pic in this link that has the bearings in front of the pinion

http://www.moparts.org/Tech/Archive/axle/1.html

Maybe if you could bore the 741 to accept the large tapered ring.

It's really much ado about nothing. The 741 isn't weak like that stupid article on the net implies. The pinion and bearings ARE NOT the weak link in the pumpkin!

 

[wstreetrod]

Not sure what I'm going to do until I get the 741 back in and test drive to see if the whine is gone, it is driving me nuts. This is just a street driver with a modified 360 so not too concerned about breaking anything.

Thanks,

 

[RustyRatRod]

The difference between the two is one digit.

 

[805moparkid]

According to DR Diff. {and what ive always thought} the 741 has been unjustly overlooked and if u view above posts{TECH} u will get a clearer understanding about 8 3/4 pigs, the 741 is very stong and is beefier than 9'' frauds, and the only 2 advantages of 9'' is case is beefier[GUSSETED] and plentiful,cheaper. Ive seen 10.80 cars with 741's and live multible seasons, chk out the tech above and compare pinion/bearings even on the almighty danas, 741s 742s 489s all MOPAR all GOOD, alot of things you hear is bs and has no merit just check and reserch it yourself and make ur own conclusion

exactly... if i remember the 8.25 is still a coulpe thou bigger than a D60...

the real issue with any drop out is ring gear deflection...

 

[oliver]

All cases neck down to the same minor diameter and the 742 and 489 have a 90 degree cut where it necks down. the 741 uses shims to set the preload on the pinion where as the other cases use a weaker crush collar. The 741 is underrated.

 

[805moparkid]

All cases neck down to the same minor diameter and the 742 and 489 have a 90 degree cut where it necks down. the 741 uses shims to set the preload on the pinion where as the other cases use a weaker crush collar. The 741 is underrated.

742 also uses shims

 

[fishy68]

742 also uses shims

Correct. Only the 489 used a crush sleeve but if you want to eliminate it they sell a eliminator kit for about $25-30. That's what I do with all 489's I set up.