To brace or Not to brace? That's the question

[dutchrunner]

Plans for 572 hemi :groucho: are getting very close now.
Will be 750hp and already have CRT 727-4 , so tranny is good.

Have 8 3/4 with 489 and 3.23 with plate style clutch.

I have 2 options:

1) Brace my 8 3/4 and just overhaul the clutch(no slip until now)
2) Overhaul Dana(Truck) which needs everything new inside( gears , bearings , diff.)

Will be maybe 3 or 4 times in the future on the strip but without slicks , ET street only.

Think bracing 8 3/4 should be enough for the engine , but just wanted to know what the raceguys are thinking?


All info welcome

 

[Hoosier Bird]

I'd go with a Dana 60 but that's just me.

 

[droptop]

Brace the 8.75. The added weight from the dana is quite substantial. :cents:

 

[69hemibeep]

Brace the 8.75. The added weight from the dana is quite substantial. :cents:

Its un-sprung weight and helps with traction so its a toss up. If you promise never to put sticky tires on it your probably fine with the 8 3/4 they are fairly stout. If your were running a standard tranny no way.

 

[dutchrunner]

Dana may be stronger but 8 3/4 is complet except for brace.
Think it will be $900,00 to get Dana ready.

So no sticky tire and just brace my self.

 

[george68hemirr]

dana 60/powerloc high performance is bullit proof....8 3/4 will work for a while but that hemi is a torque monster

 

[mcmopar]

That Hemi will destroy the 8-3/4 sooner or later. One thing I have learned in this car hobby - do it right the first time and don't cut corners. Yes, the Dana will be more expensive up front - but down the road it will pay for itself. An old saying goes;" There is never enough time (and/or money) to do the job right, but there is always enough time (and/or money) to do it over."

 

[69hemibeep]

As long as the tires are burning there isn't much stress on it, even a drag radial with that monster is going to shorten its life. So I can draft a contract that if you do abuse it with a sticky tire the car goes to me, that will simply keep you honest :jester:

 

[george68hemirr]

what i said :groucho:

 

[moparchris]

8.75 will work fine. A Dana obviously will be stronger. Both will have spider gears which is the weakest link and both diffs have similar sized spider gears. I have an 8.75 that I built for a friend that has a 900hp wedge in front of it and its lasted year after year of drag strip abuse. Depends on who sets it up, and a spool will make it much stronger. A brace for the 8.75 wont do much since that is not where the stress is. BTW a spinning tire is what kills rear ends. For example you put your ET streets on anad go out and do a couple of burn outs then try to launch the car and it spins slightly. Well it will shake and when it does it will rip the teeth off the pinion. So either go with a drag radial or try not to abuse it. The Dana will be more resilient to this. I have done it with a small block on nitrous. The car shook and off with the teeth. :cents:

 

[george68hemirr]

aftermarket axles would help also.......my buddy wwho owned my roadrunner side stepped his clutch at about 6500-7000 rpms and snapped his axle

 

[69hemibeep]

8.75 will work fine. A Dana obviously will be stronger. Both will have spider gears which is the weakest link and both diffs have similar sized spider gears. I have an 8.75 that I built for a friend that has a 900hp wedge in front of it and its lasted year after year of drag strip abuse. Depends on who sets it up, and a spool will make it much stronger. A brace for the 8.75 wont do much since that is not where the stress is. BTW a spinning tire is what kills rear ends. For example you put your ET streets on anad go out and do a couple of burn outs then try to launch the car and it spins slightly. Well it will shake and when it does it will rip the teeth off the pinion. So either go with a drag radial or try not to abuse it. The Dana will be more resilient to this. I have done it with a small block on nitrous. The car shook and off with the teeth. :cents:

Mine always came apart when I hammered it and the traction was good, God knows I busted enough of them, I guess it could be do to fatigue your the guru. :worship: I know in the dunes if the sand is wet things break.

 

[george68hemirr]

your really not having any fun unless your breakin shit....but getting rid of the weak links makes it last longer :groucho: :groucho:

 

[dutchrunner]

I think it will be the 8.75 then.
Will not be racing , or maybe 3/4 times in coming 4 years.
528RB has 600+ torq , and 8.75 stayed toughether.

Strange axles will be good advice then.

Just wana have fun on the Autobahn.
Not going allout racing anyway.

Good thing about 8.75 is that I also have 3.91(489) stand-by .
Dana swapping gears is not an option.

Think it's always a question of how strong are all te components.
Read on other forum 1 guy broke gears with 500hp and other run 1000hp without braking it.

So just have to see if 8.75 survives and if not , it's like George said.

"removing the weakest link makes it stronger"

Thanks for all the input.

Will keep you guys updated about 572?! and XFI which will go on that engine.

 

[droptop]

The weakest link in an 8.75 is the housing. Under hard acceleration, the deflection in the housing causes the ring gear to pull out of the pinion gear. When it gets to far out of the teeth, it just breaks the teeth off of the ring gear. Beef up the housing. :cents:

 

[69hemibeep]

The weakest link in an 8.75 is the housing. Under hard acceleration, the deflection in the housing causes the ring gear to pull out of the pinion gear. When it gets to far out of the teeth, it just breaks the teeth off of the ring gear. Beef up the housing. :cents:

Now it all makes sense, braces to keep your teeth straight :rimshot:

 

[ACME A12]

Sounds like you have this already decided, but I'll point out another reason to (at least in the interim) use the 8.75". Dana 60 diffs from trucks are generally too wide and have different tube ends than those for cars - they are full-floating while cars are semi-floating. Also they do not have provisions for a bolt-on pinion snubber - although this may not be concern for you. Truck axles can be converted for car usage by changing the tube ends as you'll need to cut it down anyway, but if you're just trying to limit the intial $$ expendature this won't help either.

Several good articles have been written about the Dana 60 vs. the 8.75". One in particular that I remember was written by Steve Magnante after he tested both in his Dart. Despite the added weight the Dana provided no ET penalty and was without question the stronger of the two. Long term the Dana should be your plan. There is a reason why Ma MoPar used them in the first place. :cents:

 

[Big John]

8 3/4 with 10.5 slicks. Never broke it.



Pic is from the late seventies and the car was about a half second faster.... I musta been playing games with the clock that day.

 

[george68hemirr]

Plans for 572 hemi are getting very close now.
Will be 750hp and already have CRT 727-4 , so tranny is good.

back to this beginning.....750 rear wheel horsepower

 

[dutchrunner]

Truck axle already right size.
George : it;s crank hp not axle hp.

The biggest issue for me now is the parts i need for the Dana.

Can always detune hp a little with XFI.

And if axle is changed in future just increase it again by changing data in ECU en opening TB's more.