Whos running over 700whp on an 8.75?

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Ask Dr. Diff about the weight difference between a Dana 60 and a 9". He'll tell you it's negligible and that the Dana 60 is more efficient.
 
GTX JOHN said:
I have been doing this a long time = My vote is to put in the
Dana for sure. I used to break plenty of 8 3/4 stuff with 3400 Lbs
with a 4 Speed and 550 HP!!
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Yup! Amount of power/torque vs weight/mass being moved coupled with the shock load, manual or automatic.

Do you feel it would have held up measurably longer at a weight loss of 400 lbs.?
 
rumblefish360 said:
Possibly. How many have you broken, at what weight with how much torque?
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I haven't weighed the car yet. The aftermarket K and rack and pinion is definitely lighter than the factory one and steering box. The links are lighter than the leaf springs and the aluminum heads and plastic intake are certainly lighter than the stock cast ones. So realistically its probably closer to 3000 but I was just saying 3400 to be generous. Around 700ft/lbs of torque. I've only broken one, but at $1600 a whack, I have the 60 and I can built it for the $1600. Weighs the same and is much stronger so seems like a win win.

I will also add, I have had every part of that car apart and upgraded besides the rear diff. That was basically a 50yo rear end getting served a hot supper.
 
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70DusterDev said:
I blew the caps up on my 8.75 at the strip this fall after getting my car finished and tuned, so I got a complete new Yukon 3rd and am going to replace the broken caps with the billet ones as a spare. (found out about the caps after I bought the new 3rd)

We set my car at 750whp this summer because of running out of injectors/pump, but it made 779 with maxing the injector duty cycle. I'm swapping injectors and pumps this winter to go back and break over 800 hopefully.

I have a dana 60 and all the stuff in a cart from Dr. Diff to build the 60 to swap into my car, was just curious before I do if anyone is running an 8.75 with with big power or if I should just do the 60. I also have someone lined up to buy the 8.75 for the $1600 I spent on the 3rd (nevermind the cost of chromo/green bearing shafts). Just sucks I'll have to have my driveshaft cut down for the 60 (its already 1350 joints) and I'll have to move my 4 link mounts on the chassis which is fine since I did all the fab myself, it just adds more to the to do list with a 60. Its a 70 Duster. Probably weighing around 3400lbs or so.

View attachment 1715844048
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I'm happy with my 8.75. They are pretty strong.
 
70DusterDev said:
I blew the caps up on my 8.75 at the strip this fall after getting my car finished and tuned, so I got a complete new Yukon 3rd and am going to replace the broken caps with the billet ones as a spare. (found out about the caps after I bought the new 3rd)

We set my car at 750whp this summer because of running out of injectors/pump, but it made 779 with maxing the injector duty cycle. I'm swapping injectors and pumps this winter to go back and break over 800 hopefully.

I have a dana 60 and all the stuff in a cart from Dr. Diff to build the 60 to swap into my car, was just curious before I do if anyone is running an 8.75 with with big power or if I should just do the 60. I also have someone lined up to buy the 8.75 for the $1600 I spent on the 3rd (nevermind the cost of chromo/green bearing shafts). Just sucks I'll have to have my driveshaft cut down for the 60 (its already 1350 joints) and I'll have to move my 4 link mounts on the chassis which is fine since I did all the fab myself, it just adds more to the to do list with a 60. Its a 70 Duster. Probably weighing around 3400lbs or so.

View attachment 1715844048
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My big heavy Van with 400hp and no problem with 8.75.

IMG_20211122_224958_729.jpg
 
Very late to the game here, and I haven't read a lot of this thread yet, but my philosophy is this : if you think you might need a Dana, you NEED a Dana. I would not trust a 450hp stickshift car in front of an 8 3/4, let alone 700.
Fix the 8 3/4 as a street rear, sell it to a street guy, and put the Dana in.
 
Who is running an 8 3/4 with 700 horse?

nobody, they are all broken!
 
:rofl:
70DusterDev said:
400hp and 750hp are quiiittteee a bit different, even with a bit more weight.
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Yeaaaaa, just a bit I’d say.

Thanks for the very informative description above. This is a lot better than most. It seems to me that after reading many posts through out the years on this dead end, at or about the 600 lbs of torque is where I gets dicey. Weight and the way the car is launched also plays a big part in the time bomb.

Currently I have a 8-3/4 in my Duster that is going to get a lightening program done on it. But it won’t be a full tilt effort. I have no illusions that the rear will last under the planned engine. (small block)

For now and for a while it’ll be run with the stock K frame and SS leaf springs.
 
@33IMP FWIW, I have no issues with mine at that power level in TQ & HP. 360 4spd 4.10 ‘73 Cuda, PS-PB car, 30 years now.
 
70DusterDev said:
Same thing just happened to me when I looked it up
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I found my post where I measured the actual weights of a 8 3/4, came in at right around 200 lbs WITH brakes. I find it hard to believe that a 9 inch housing and an 8 3/4 housing weigh all that much different. The 3rd member vs center section I can see a difference as the 9 inch is beefier and oval shaped vs round.

I would think the axle housing tubes of a 60 would weigh as much as the entire housing of a 9 or 8 3/4.

Not arguing just surprised
 
rumblefish360 said:
@33IMP FWIW, I have no issues with mine at that power level in TQ & HP. 360 4spd 4.10 ‘73 Cuda, PS-PB car, 30 years now.
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You are right, for you. I guess I come at it from a traction standpoint. With slicks, an 8 3/4 will last a while, but I wouldn't trust it, and I think I would replace it before I broke it. Heck, Mopar put a Dana behind a 375 horse 440, with a stick, and a 390 horse with a 727.
 
Dana67Dart said:
I found my post where I measured the actual weights of a 8 3/4, came in at right around 200 lbs WITH brakes. I find it hard to believe that a 9 inch housing and an 8 3/4 housing weigh all that much different. The 3rd member vs center section I can see a difference as the 9 inch is beefier and oval shaped vs round.

I would think the axle housing tubes of a 60 would weigh as much as the entire housing of a 9 or 8 3/4.

Not arguing just surprised
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Dana weight varies greatly, depending on heavy duty truck axle tubes, or car tubes. I don't think the current crop of aftermarket race Dana's are all that much heavier than an 8 3/4 or nine.
 
RustyRatRod said:
Here's a good article about the Ford 9" compared to the Dana 60.
The 9-inch Ford Rearend is the Strongest Rearend Out There—It’s All Due to “Hypoid Distance”.
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When the article mentions the "massively heavy nine inch dana" the article loses some credibility, and the bias (from a company that builds nines, almost exclusively) is readily apparent!
They also conveniently forgot to mention that those strong nines are LOADED with aftermarket parts.
A Grey iron center, weakass Ford posi, 28 spline axles stock nine inch isn't even in the same area code as a stock Dana 60, strength wise.
 
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