What is next best 8 3/4 case under the 489

[Meep-Meep]

The 9" has longer ring gear teeth and the lower pinion requires a different helix cut, which I believe takes more load off of the pinion bearings. Yes, the 9" pinion bearings are smaller than a 741, but we are also talking about a very different design.

I believe the reason the 9" became the industry standard is they are easy to set up, plentiful and overall a strong unit. The track lock is the weak link and if you will do anything serious you need the billet carrier.

I have seen 741's go through some abuse and come out OK but there is also a reason the factory made the 742 and then the 489.

 

[RustyRatRod]

The track lock is the weak link............

You sure were kind with your words. Let me make it clear. The track lock is a piece of crap. How's that? lol

 

[67 coronet]

the 9 inch became the racing standard because back in the day they were tons of them in junk yards and the removable third member made for fairly quick gear changes.8 3/4 rears never had the availabilty of the 9 inch and chevy never made a strong drop out third member,so there you go.the aftermarket picked up on there use and built tons of parts for them.same problem we mopar fans have with lots of our stuff.

 

[Cranky]

Yup, drop outs make for easy gear changes but it still takes about the same amount of time to initially set one up. That's great for someone buying the drop out that's already done but they are getting pretty expensive with the prices of around 500 bucks for the 8 3/4 with SG in it. I know how to set up my own so I'm just going to buy a set of gears for around 1/3 of the price and go for it. Also, on a Dana type rear, if you want to change gears, all you have to do to save the old set up is to tag the shims for that ring and pinion or write down what shims that gear set had and put it in a box. Then if you ever want to go back to those gears, you can do it in about the same amount of time that it takes to swap a drop out. And I agree about the Track Locks....they're junk.

 

[Cranky]

Here is an interesting article on the 8 3/4
http://www.carcraft.com/techarticles/ccrp_1210_sure_grip_chrysler_differential_swap/

Did you read the article? They identify a cone type SG as a clutch type. Could be a typo and maybe not. Seems I remember it was in a Car Crap rag that I first read that the 89 was sooooo much better than the others back in the early 80's.

On another note, most times I see a cratered 8 3/4, it's shaved teeth either from pinion or bearing cap deflection. There's a reason why they make a cover girdle for the Dana 60 but that's kinda hard to do with the 8 3/4.

 

[Budnicks]

I don't think it is. The phord has front pinion support, where the 8 3/4 does not.

:iamwithstupid: Ford 9"- The pinion is supported on both ends for the people that don't know, there are some prefered cases with the Ford 9" also, not all are equal ins strength either, they break also, most use aftermarket units or Nodular Iron cases when making decent power, But typical like most non Mopar products, 9" Fords are readily available... Like it's been said before, if your in doubt, with the 8-3/4", then go with a Dana 60 or the even stronger S-60 from Strange Engineering, Moser Engineering sells some decent parts for Both styles...

 

[Meep-Meep]

You sure were kind with your words. Let me make it clear. The track lock is a piece of crap. How's that? lol

......Or....I suppose you can say it like that.

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As long as we are on the subject don't forget the early Olds and Pontiac rear ends. With its 9.3" ring gear those were found under many gasers back in the day.