Rear End Numbers

[Black340]

Can anybody tell me what this numbers represent ..thank you

[73Chally]

I don't know a whole lot about these, but I do know the most important number is the 741, which identifies the type of case (as opposed to a 489).  I never can remember which one is considered better than the other, or even what the differences are, but hopefully that's a start for you.

[Chryco Psycho]

741 is the lightest duty center section , with a 1 3/8" pinion , 742 is 1 3/4" & 489 is 1 7/8", 742 is considered the strongest due to better design & parts used

[Black340]

741 is the lightest duty center section , with a 1 3/8" pinion

Is That bad?

[73Chally]

Depends on your motor.  If you're running a stock 318 then it would most likely be fine, but if you're looking more at a 340/360 or big block, then it probably would not stand up to the increased power output.

[Black340]

Holly cow!!! I have a 340 with  4 speed trans..What I can't understand is that that is the original rear end why the factory will place such a combination if like you say will not stand up to the increase power output

[73Chally]

I might be a bit off on my estimations, but thats the general idea.  I guess it might apply more to trucks and towing.

[ted]

I HAVE  a 741 behind a mild 360, no problems.

[tactransman]

Slicks would kill it,you will probably be fine.

[Chryco Psycho]

I bet you cannot hurt it , unless you have slicks & traction even behind a big block , generally as long as the tires will spin you will not hurt the diff / gears