489 vs 742

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that is like the poly vs rubber question--- there are threads on here with lots of opinions.

Use the one you like best or is the easiest for you to make what you want-- both are desirable options. Lawrence
 
The 489 has a thicker pinion, but all the 3 types all neck down to the same size near the splines.
And when they break, the bearings caps and ring gear teeth are the first to go. Usually not the pinion.

You think you're making enough power to break one?
 
The big difference between the two is sure grip 742 uses clutches and the 489 uses cones.
The only 8.75 I ever broke was an open 741 and the spider gears went.
Use which is in the best shape and you will be fine.
 
BigBlockMopar said:
The 489 has a thicker pinion, but all the 3 types all neck down to the same size near the splines.
And when they break, the bearings caps and ring gear teeth are the first to go. Usually not the pinion.

You think you're making enough power to break one?
Click to expand...

There's one exception to the rule that they all neck down to the same size. Fine splined pinions used in later 489's are a larger diameter than coarse splines. But I agree that's not where they usually break first anyway. I usually see the ring gear teeth go first.
 
Black 69 Dart said:
Whats the difference between the two center sections? I have one of each and but wondering if either is stronger?
Click to expand...

My question to you is;

Are you planing on making approx. 750 - 800+ HP?

If not, then you need not worry.
 
The 742 is in the car now, has Richmond gears, strange spool and axles. The 489 has Richmond gears and rebuilt posi. Reason I am asking is I am thinking of adding a billet yoke, caps and was wondering if the 742 would be worth adding to or build the 489. BigBlockMopar asked if I am making enough power to break one? I hope to :D I am shooting for 1000 hp with the new hemi and some boost.
 
1000hp ... and you are even considering a 8.75???

Do not pass go, do not collect $200 :)

Ditch the 8.75 stuff and get a Dana60 or 9"
 
I am with cracked go with a dana 60 with that much power.
It will be cheaper in the long run when the 8.75 goes bang and tears up the trans, drive shaft, floor boards or causes an accident.
 
Yep, Cracked nailed that one. WHOOO! Big power! Nice.

I've seen 8-3/4 handle 750+ fine enuff. But they do surrender after a while. At 1000hp, they will break. The 8-3/4 may handle it if it were all new with the aluminium housing and billet parts and a brace on the tubes etc.... IDK for sure though. I ain't been there myself.
 
I agree fully... Sell both units And the rear axle and get a Dana60!
When a rear end breaks, it takes out your transmission sprag aswell usually. Think of the savings you make by going Dana right from the start :)
 
I was thinking the same thing was just considering if it would be worth building an 8 3/4 would be worth it or could handle the power.
 
BigBlockMopar said:
The 489 has a thicker pinion, but all the 3 types all neck down to the same size near the splines.
And when they break, the bearings caps and ring gear teeth are the first to go. Usually not the pinion.

You think you're making enough power to break one?
Click to expand...

Wrong on this one the 742 front bearing near the yoke dwarfs the 741/489.
Like mention in post number 2 Search this subject it has been cover/beat to death.
 
Naw, build the 8 3/4. Use any center section you want. Hell, use them all at the same time. Just please post the pictures of the carnage. Of the friggin EXPLODED parts that you can find!!!! JK, do the 60.
 
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