741 + 489 8 3/4 diff casting = ?

[edl94]

There is a story in the oct issue of car craft under the heading Junkyard Builder about 8 3/4 diff center sections. It covers removing the dana sure grip from the wimpy 741 and installing it in the stronger 489 case. Someone down the line removed the stock 489 one leg from my cuda and installed a 741 sure grip with 4:10 gears. They saved the 489 with 3:? gears and passed it along with the car. I need to go check the gear ratio when I get a chance. The story states that you can remove the good dana sure grip and install it in the stronger 489 case with a non collapsible collar and shim set. I have all of the parts and it would only cost me the price of the collar gasket and shims. I upgraded to a 440 that might test the limits of the 741. Has anyone done this swap? What do you guys think is it worth it? The diff is the only part I did not go through. Also what is the best all around gear ratio 4:10 is too low for freeway driving. Although it won't see the freeway much I don't want to kill it on a road trip.

[Chryco Psycho]

not quite sure what you are asking but
 the 741 carrier will bolt into the diff easily .
 the sure grip in the 741 can be swapped to the 489 making the 489 a sure grip diff but ti will retain the 3.?? gears .
 the 741 gears cannot be swapped into the 489 carrier

[edl94]

That was basicly my question will the sure grip fit. Just checked the ratio on the 489 it's 3.23 not good for what I want to do. I will get it going with the current setup and see how the 4.10 gears feel on the freeway etc. then do the sure grip swap with new gears. I am thinking 3.73 or 3.91 might be a better setup for the way it will be driven. I think the added strength of the tapered pinion and non collapsible collar will be worth it.

[Chryco Psycho]

makes sense , or just use the 741 until it has a problem & switch then , I doubt you will hurt the sure grip unit , , I doubt you would hurt the 741 either unless you use slicks at a track .