Whos running over 700whp on an 8.75?

[70DusterDev]

@DoctorDiff what do you think?

Cass was actually the one who recommended me build a 9 or 60 to begin with when I told him my HP rating after breaking the current 3rd. He's who I'm buying all the 60 parts from. I was just curious if anyone is getting away with the bigger power and the 8.75 simply because its the easy way out. Though I shouldn't kid myself because all I do is beat on the car when I drive it lol

 

[RustyRatRod]

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!

I suspect there's a reason they build nines almost exclusively.

 

[SGBARRACUDA]

I ran a 742 with a spool and 35 spline axles 4.88 gear and 4.56 gears. 71 Dart ran consistent 6.04-6.10 1/8. For many years. SS springs with snubber. BB. 29.5 W Slick. Don’t know what the HP was.

 

[70DusterDev]

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

This post bellow is what I was going off for an 8.75 which is right around the same weight as the 9 and 60. It seems that they are all about the same ballpark. Especially since the flange ends are the same mopar bolt pattern/size and using all the mopar brakes. The perch for the 60 is the same as the 8.75 too one being 3" and the other being 3.125 so there really isnt toooo much of a difference in the size there either.

 

[70DusterDev]

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.

It seems this is going to be the plan. I already have the 8.75 sold if I dont use it to a guy with a hemi swapped scamp local to me. It'll work great for him.

 

[70DusterDev]

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.

This needs a "love" response instead of "like" or "thanks" haha

Thats why the 9" wasnt even in the question because the weights similar to a 60 and I'll have twice the money in it for the strength. I already own the 60. Its sitting in the garage right now waiting to be cut apart.

 

[33IMP]

I suspect there's a reason they build nines almost exclusively.

Let me be clear, I have great respect for nines, I have two in cars with 14"slicks, I know how strong they are (if you put good parts in them). And the gear ratios available is a big plus compared to a Dana.
I just think a Dana looks much better in a Mopar, the weight thing is overblown, and a killer strong Dana can be done for a lot less money than a nine. I have been getting by with my 8 3/4, but I should put in a Dana before I bust it.

 

[RustyRatRod]

Let me be clear, I have great respect for nines, I have two in cars with 14"slicks, I know how strong they are (if you put good parts in them). And the gear ratios available is a big plus compared to a Dana.
I just think a Dana looks much better in a Mopar, the weight thing is overblown, and a killer strong Dana can be done for a lot less money than a nine. I have been getting by with my 8 3/4, but I should put in a Dana before I bust it.

Hay, I don't have a dog in the hunt. I don't really give a crap. I was just posting up what seems like good information from experienced sources.

 

[318willrun]

What do you want to know? I will start a thread, look out for it.

Everything about it that you know and I don't ! Besides, a guy with a Van like that should have more than 2 likes (I just gave you your 3rd) lol

 

[318willrun]

It seems this is going to be the plan. I already have the 8.75 sold if I dont use it to a guy with a hemi swapped scamp local to me. It'll work great for him.

The 8.75 is a very strong rear end, and came behind most of the Mopar muscle cars, including 440 Magnum/Commando B-bodies weighing close to 4k lbs. But with todays tires that bite, and with over 300 more hp than anything Mopar built back in the day, even in a A-body it has no chance to live. Dana 60.

 

[rumblefish360]

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.

True X3
My car is a street car.

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.

 

[TT5.9mag]

I think if you have the D60 already and all it needs is shortening and flanges/brackets welded on your answer is easy. Use the D60. IMO though at your power level even a stock D60 won’t last too long. You need a fairly well build rear end. I looked at quick Performance stuff a while back and you can put together a pretty beefy 9” that will hold 1000+ hp for about $2900.

 

[rumblefish360]

That becomes cheap if you start thinking about what else could break.

 

[TT5.9mag]

It takes big boy $$$ to play with big boy horsepower. And if @70DusterDev is anything like me, 1000 hp is only a couple twists of a screw and a few keyboard stokes on a turbocharged deal, he will turn it up. I always do.

 

[70DusterDev]

I think if you have the D60 already and all it needs is shortening and flanges/brackets welded on your answer is easy. Use the D60. IMO though at your power level even a stock D60 won’t last too long. You need a fairly well build rear end. I looked at quick Performance stuff a while back and you can put together a pretty beefy 9” that will hold 1000+ hp for about $2900.

So I have the 60, but all I'm using is the housing. I'm upgrading to a 35 spline suregrip posi along with the new 35 spine shafts/green bearings from Dr. Diff. So it certainly wont be stock. I'll be $1600 in it with all the parts. Even less if the 60 I have is 4.10. I gotta crack it open, because if it is then I can use those gears again.

 

[70DusterDev]

That becomes cheap if you start thinking about what else could break.

You aren't shitting, I just had to ship back the 800hp McLeod clutch since it was already slipping and upgrade it to the RXT1200 to be rated for 1200hp. After this and the 60 rear I know the T56 is gonna die and I'll have to put a Magnum in it, but hopefully this lasts me a year or two.

 

[rumblefish360]

It takes big boy $$$ to play with big boy horsepower. And if @70DusterDev is anything like me, 1000 hp is only a couple twists of a screw and a few keyboard stokes on a turbocharged deal, he will turn it up. I always do.

Yea man! You have it all in your build thread right?

 

[70DusterDev]

It takes big boy $$$ to play with big boy horsepower. And if @70DusterDev is anything like me, 1000 hp is only a couple twists of a screw and a few keyboard stokes on a turbocharged deal, he will turn it up. I always do.

You know it. Idk if I'll break the 1000whp mark but if I can get into the 850whp range like we think its going to with the new injectors and pumps thats knocking on 1000hp!

 

[Oldmanmopar]

My engine made 829@7900 at the crank on an engine dyno . The Duster weighed 3850 with the driver. All original spare tire in the trunk, Mini tubbed with an original length braced 8 3/4 housing leaf springs 456:1 gears and a 5500 stall.

8 years of street racing then 2 years after it was tired at the track and never a problem with the rear. Always foot braked. We are building a bigger small block for now and going to a Big Block. We are staying with the same rear for easy gear changes from 1/8-1/4. we might narrow the housing 1 inch per side to use centered wheels not sure. The new car will be under 2800.

Housing flex is the killer for the 8 3/4. We are thinking of going with a moser fabbed housing. If the 8 3/4 Grenades then its a Fab 9. Danas can get expensive if you have to keep replacing the housing. Been there. Nothings blow proof.

Years back when you pulled up behind a car with a Dana they looked cool. Today There like and iron old 426. They look good in old school cars but very heavy. Who wants to carry a whole rear in the race trailer for a spare. And then try and change it between rounds if something does happen.

When going from a 275 or small tire class to a 315 or big tire, and the 1/8 to 1/4 I prefer carrying prepped center sections. That's just me for a race car. If I had and old R/T , GTX or any old mopar street car where the look and strength mattered and was never playing with gears or tires. Its definitely a Dana

All my RR's and B'bodies in the past had Dana trac-lock 410's

 

[70DusterDev]

Yea man! You have it all in your build thread right?

Yeah I do, I'll be adding the dana 60 upgrades to it as well to follow up with the rear end blowing up.

 

[TT5.9mag]

So I have the 60, but all I'm using is the housing. I'm upgrading to a 35 spline suregrip posi along with the new 35 spine shafts/green bearings from Dr. Diff. So it certainly wont be stock. I'll be $1600 in it with all the parts. Even less if the 60 I have is 4.10. I gotta crack it open, because if it is then I can use those gears again.

Certainly not a bad plan. And it should hold up well. I just think you’re beyond that at this point. On our race truck we run a full fab 9” housing with 4” tubes with a strange 9+ center section with a spool and 40 spline axles. We are at 650hp and 5300lbs on a 37” tire. We replace gears after every race. We broke a lot of rear ends to get the point of only doing gear changes and would have saved a lot of money had we started with big boy ****.

 

[70DusterDev]

Certainly not a bad plan. And it should hold up well. I just think you’re beyond that at this point. On our race truck we run a full fab 9” housing with 4” tubes with a strange 9+ center section with a spool and 40 spline axles. We are at 650hp and 5300lbs on a 37” tire. We replace gears after every race. We broke a lot of rear ends to get the point of only doing gear changes and would have saved a lot of money had we started with big boy ****.

Yeah that is quite a bit more weight and WAY bigger tire putting quite a bit more stress on all of the drivetrain. Again this is a street car 90% of time with a couple trips a year to the strip. So thats a totally different kind of abuse. I think the 60 should hold. Hopefully haha

 

[gzig5]

I think all the cars running 8 3/4 diffs at 700+hp successfully are also running Cooper Cobras or BFG T/A’s.

 

[TT5.9mag]

Yeah that is quite a bit more weight and WAY bigger tire putting quite a bit more stress on all of the drivetrain. Again this is a street car 90% of time with a couple trips a year to the strip. So thats a totally different kind of abuse. I think the 60 should hold. Hopefully haha

I agree it’s a different animal all together. I just referenced it to make a point. But like I said, if I had the D60 I’d at least try it.

 

[Oldmanmopar]

I think all the cars running 8 3/4 diffs at 700+hp successfully are also running Cooper Cobras or BFG T/A’s.

29x14.5 15's Hoosiers on 12 inch wheels. like I said foot braked 829 at 7900 at the crank. Coopers are all season tires. LOL