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View Full Version : Mopar 8 3/4 (8.75) rear end , strongest ?


Blown340cuda
03-08-2005, 11:52 AM
Hi Guy's

I have several 8 3/4's and i was alway's told that the 489 cases where the strongest, well in many cases that's true . But i have a couple of 742 case that have a thicker pinion neck then the 489 cases, also i have a 742 case out of a 67 rt and it as the large flange (1350) , if you ask me the only thing that the 489's have better then the 742 is that the raer caps are widder and the 2 ribs on each one are quiet a bit larger. Now i do have one 742 case that as the same size rear caps as the 489's, now if they where replace at one point in time i do not know.

All in all I would like to get your opinions on what case you think are the strongest.


Thanks for your time!

Charlie B.

Keep on a moparing! :firedance :evil: :smoking:

dwc43
03-08-2005, 01:01 PM
They are all pretty equal in strength. I have yet to break any of them. :cool:

TK
03-08-2005, 01:06 PM
hey! can anyone tell me the difference between a RA36, and a RF36???
they are both 8 3/4 truck rearends.

zij576ca
03-08-2005, 02:14 PM
I use the '742 case exclusively and the only thing I ever did was twist an axle. '742 should give you years of trouble free service. It comes down to what do you have and what is your preference? Either one should be fine.

John Kunkel
03-08-2005, 03:58 PM
The rear pinion bearing in the 742 has 15% more load carrying capacity than the 489, this makes it the strongest overall.

Mopar chose the 742 design when making the aluminum housing.

DartGT66
03-09-2005, 03:20 AM
Even the smallest 741 pinion is thicker than a Ford 9" pinion. I have never heard anyone breaking a 8 3/4" because of a too thin pinion, nothing htat even could be related to that. Puking out teeth of the gears and breaking bearing caps are the usual ways they break.

dwc43
03-09-2005, 08:21 AM
The reason they break bearing caps and gear teeth is due to axle housing flex and is the main reason that the 8 1/4 replaced the 3/4 axle. :D

Blown340cuda
03-09-2005, 11:21 AM
well all i can say is that i grenaded several 8 1/4 rear but never did grenade a 8 3/4 except for 1 741 case the right bearing cap broke and ruined the party. I would take a 8 3/4 anyday over a 8 1/4 rear. Don't even have to think about it. the only rear i would replace my 8 3/4 (489 or742 case) is a dana 60 if you have 600 hp or more. But what i was interested in knowing is if the 742 or 489 is the strongest. guess it's a pretty close match.

Blown340cuda
03-09-2005, 11:28 AM
oh and the ford 9" well they grenade often too, my brother the flord man grenaded several in is mustang, he's actually running a dana 60 in it now and it's track tortured all summer long , in 3 years the only breakdown was breaking a few teeth of a 4.56:1 richmond crown.1 set of gears is not bad for 3 years of fun! He's a big ford man and he swears by the dana 60.I told him he should get rid of that 429 and drop a 440 in , but he told me to @#$^ off hehe.

pishta
03-09-2005, 11:33 AM
You have a choice between a crush sleeve preload and a shim system. I like the shims. Maybe the other variable to consider is the coarse or fine spline yoke.

dwc43
03-09-2005, 11:33 AM
well all i can say is that i grenaded several 8 1/4 rear but never did grenade a 8 3/4 except for 1 741 case the right bearing cap broke and ruined the party. I would take a 8 3/4 anyday over a 8 1/4 rear. Don't even have to think about it. the only rear i would replace my 8 3/4 (489 or742 case) is a dana 60 if you have 600 hp or more. But what i was interested in knowing is if the 742 or 489 is the strongest. guess it's a pretty close match.


THey are pretty equal in several ways, but both have there advantages and disadvantages. I have yet to break an 8 3/4 or 8 1/4. We've run both on dirt and asphault with great success. The dirt track racing puts a lot mroe stress on parts than any other form of racing though. Both are tough and hard to beat. Unless I was running a supercharger or hooking up really really hard, I see no use for the heavy Dana 60. Good axle though, just too heavy.

Blown340cuda
03-09-2005, 11:38 AM
Which one do you guy's think is best crush sleave or shim type for best overall preload?

:evil: :eyesbig:

dwc43
03-09-2005, 11:40 AM
Shim type is best, but harder to set up. :)