8 3/4 Diff strengths?

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hux340

hux340

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I heard there are different casting no's on 8 3/4 diffs for strengths. Can anyone please tell me them so I can check them against mine?
 
There are the 741, 742. and the 489 third members.....it has to do with the pinon diameter with the 489 being the largest and strongest.....

Jeff
 
Gee, I wonder what the 64/65 race Hemi used? 741 maybe?
 
crackedback said:
That whole pinion thing is BS.

Run what you have if it's working and the ratio you want.

Guess which pinion doesn't have a stress riser in it...

Here is a better source for 8.75 info
Pinion Comparison - Quality Body Shop Drivetrain
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Yeah...the pinion diameter at the splines is all the same, for all 3 units, as they are interchangable (spline count not withstanding),,,,so....which one is REALLY stronger??????
 
I like the 742 with the shims and big bearing, when I have a 489 set up I have the crush sleeve eliminator installed. If you ever have to replace a seal or you are changing your yoke for some reason all you have to do is retorque to specs and your good to go. Webby.
 
65Val said:
Yeah...the pinion diameter at the splines is all the same, for all 3 units, as they are interchangable (spline count not withstanding),,,,so....which one is REALLY stronger??????
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The 489 is the strongest because the shaft diameter is the largest of the 3 where the greatest load is at. The spline end is not the area of greatest load. That's why it was never changed. The ford uses a third support bearing so the shaft cannot deflect as much. Therefore it can use a smaller shaft diameter. Because the 83/4 does not use this 3rd bearing, the best way to minimize pinion shaft deflection under load is to increase its diameter. IMHO.
 
It's totally splittin hairs as to which is strongest. End of story.
 
BS on the pinion size making a difference in strength. It's not the weak point in any of the cases.

Please continue to get sucked in to the false narrative.

Ever seen a 489 case with the yoke snapped clean off? How's that for strength? Never seen a 741 do that.
 
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crackedback said:
BS on the pinion size making a difference in strength. It's not the weak point in any of the cases.

Please continue to get sucked in to the false narrative.

Ever seen a 489 case with the yoke snapped clean off? How's that for strength? Never seen a 741 do that.
Click to expand...

You can lead a horse to water, but if he's stupid, there's nothing you can do.
 
crackedback said:
BS on the pinion size making a difference in strength. It's not the weak point in any of the cases.

Please continue to get sucked in to the false narrative.
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I did say imho. Did not say they are weak. I said they deflect less under load. I know many guys who start to break gear teeth after certain performance level. Personally I think the Salisbury design overall is superior. Imho
 
RustyRatRod said:
Since when are we talkin about Dana 60s?
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I am just saying that in any instance a larger diameter shaft is alway stiffer and stronger all other things being equal. If you are trying to keep precision machined gears precisely aligned under extreme load, that larger diameter deflects less.
 
Personally I like the 742 housing the best, because it has the largest inner pinion bearing And has no crush sleeve.
 
489's and 742's break in the same places as 741's do. Been there, done that and seen it many times.

BTW, it was a good design for it's intended use.
 
justinp61 said:
489's and 742's break in the same places as 741's do. Been there, done that and seen it many times.

BTW, it was a good design for it's intended use.
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I agree with your post. But I was trying to emphasize stiffness and rigidity to maintain mesh alignment. Not outright breakage.
Most of the breakage I have seen is cap breakage and gear breakage. What other kinds of breakage have you seen.
 
I've made hundreds of passes in the very low 12s and high 11s with my bone stock 741. This is also on stock axles with small bolt pattern wheels. Just saying some of these myths crack me up.
 
Duane said:
I agree with your post. But I was trying to emphasize stiffness and rigidity to maintain mesh alignment. Not outright breakage.
Most of the breakage I have seen is cap breakage and gear breakage. What other kinds of breakage have you seen.
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As you posted most of the time they shuck the teeth off the ring and pinion gear or break the cap on the pinion side.

A 9" is a good design but unless they are in a good nodular case with a good pinion support they aren't really that strong either. My brother and I broke several in four wheel drive trucks years ago, it ruined the case every time.
 
justinp61 said:
As you posted most of the time they shuck the teeth off the ring and pinion gear or break the cap on the pinion side.
Click to expand...

Which is the weak point. Ring gear deflection/cap breakage, not the pinion deflecting. That's why it's a non issue regarding pinion bearing size.
 
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