How much can a 8-3/4 take?

[Sly Fox]

As some of you know, I'm building a 440 Challenger street/strip car that will be cranking out around 525 to 550 horse. I'm not sure of torque figures yet, but I would like it to be a little more than the horsepower. I plan on beefing the rearend up to handle the power and I'm pretty sure it won't have any problem doing it, but I just curious if anybody knows what an 8-3/4 rearend's limitations are.

Sly

[rumblefish360]

I would not worry to much. There preety tuff.
You can always, with ease, inspect the unit if your sweatin the life span of the unit.It is know for its strength.

[BugEyedValiant]

I have a 3400# a body that runs 10s with no prob. I know that you will be more than safe.

[Dart]

Are you going auto or 4sp? Are you going to run NOS?

PRO twisted an inner axle on his '67 Coronet. It had 440, 4sp, with NOS, and 3.91's.

I think the shock to the drivetrain from the 4speed is the main problem. TO slove that, I run a set of Moser street axles in my 8 3/4, but I am no where near that kind of power with my 360.

[This message has been edited by Dart (edited February 03, 2001).]

[Sly Fox]

I'm going to be using an automatic. I won't be using NOS either. I plan on putting a set of good Mosier axles in it. I also thought about putting a Mosier spool in as well or do you think a stock sure grip will hold up to that kind of punishment ?

Sly

[This message has been edited by Sly Fox (edited February 03, 2001).]

[JERICOGTX]

The 8 3/4 can take alot if setup properly. I've been running one in a 3500 lb B-body, that runs mid tens w/ 650hp and a 4speed. Its a 489 case w/Mark Williams caps, Moser spool, axles, and Richmond street gears. So with what your power range, and if running a auto you should have no problems.

[cdignition]

I know a guy who had a 440-6 Cuda who broke one of the carrier caps...this was a 12 second streeter...with slicks. Nothing big and exotic. Its hard to know if/when it will fail. And i also know a guy who runs an A/FX car that goes easy mid 9's. Also runs 8 3/4 rear.

[ChristianCuda]

Two major factors in whether or not to keep the 8 3/4 are if you have a 4-speed and good torque change it, also with an automatic with a transbrake change it. If you have more than 600 HP/TQ then you also need to change it. The shock to the drive train is what ruins a 8 3/4. If you have more than 500hp/tq then you need to have the parts of the 8 3/4 that need to be braced/replaced/upgraded done otherwise you will have broken rear end parts. 8 3/4 are good but by the time you spend the money for all the extra parts you add more weight to the 8 3/4 and the Dana is looking alot better for stability. If you can get a Dana for over 500hp then do it. Otherwise playing the tightrope game with the 8 3/4.
Now again with a automatic and no brake then the 8 3/4 will last longer then if you put in a brake.

On the suregrip yes it will hold for how long don't know. If it were me I would go with a spool or locker.

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Http://ThunderRacing.Knudstrup.net/

68 'Cuda 383 Best of 8.363@83.78 in the 1/8mile which is a mid 12 with a 1.89 60ft
Formula S recreation not original but making like they should have at the factory) Working on adding EFI
69 'Cuda Race Parts Car
76 Duster 273 recent transplant
95 Neon 2.0 SOHC best of 16.96
84 Dodge Ram D50 transplanting 360

[bbaspense]

My father in law went 8.70 in a Rustang with NOS. He had the back braced and Moser axles...that's it. 1.28 60 ft off a trans brake. It will take it.

For all out racing I wouldn't use the heavy Dana 60. I would use a Phord 9 inch.

Jason

[JANDJ]

HELLO, JERICOGTX, YOU MENTION THE MARK WILLIAMS CAPS, DID THEY REQUIRE MACHINING WHEN YOU PURCHASED THEM AND HOW MUCH DID THEY COST. I WAS THINKING ABOUT GETTING THEM AS I BROKE A CAP LAST YEAR IN A 489 CASE. I CURRENTLY AM USING A 742 CASE THAT I DID A FEW MODS ON INCLUDING SOME SPECIAL BOLTS BUT I DID NOT REPLACE THE CAPS. JUST WOINDERING

[Cuda4play]

Today I went by a ricer and dicided to WOT for a few secs...I mashed the pedal to almost 5,000 rpm,I heard the usual echo,but also I and my buddies down the street heard another echo comming from the rear,.did i mess something up in the rear end or converter?

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Massively Over-Powered Asphalt Ripper

[JERICOGTX]

JANDJ the caps are $75 each and come with new bolts. Yes they do need to be machined to fit. They come about 0.100 extra, this way they can be milled, and ground with a cap grinder to fit you center section. They are not a "ONE SIZE FITS ALL" deal. If you do get them make sure you get them for both sides. Some people get away with them only on one side, but if you already have it apart do them both!
PS The caps did take a little while to get from Mark Williams but they are the only ones who make them.

[Dart]

Hey Sly Fox:

The stock suregrip will be fine, but you may want to look at one of those new Power-Trax lockers they are showing in Summit and Jegs. The price is right and they aren't supposed to wear out like the suregrip does. The install is easy also as you don't need to take the 3rd member apart (I think) to put it in. Besides I thik they are around $300, way cheaper than setting up a new 3rd member for the 8 3/4.

p.s. - I think you will be fine with the 8 3/4. If you were 4sp and NOS and making serious HP (>550) you would need to upgrade the 8 3/4 in a few areas to be safe. I love my Moser axles...

[ChristianCuda]

bbaspense

This has been stated and proven elsewhere so I won't go through it all again here. but I will state it.

The Dana is heavy yes but by the time you add all the added strengtheners to the 8 3/4 it is only shy of the dana by 30 pounds. The Phord 9" is terrible because of the low pinion. It also needs tons of bracing and really is as heavy as a Dana.

Out of the three mentioned I would pick the Dana that stock will handle the horses the 8 3/4 will when it gets built to the hilt. And you will have the same money in the Dana or the 8 3/4 and the Dana will take more HP and TQ. The 9" on the other hand will cost cheaper brake more often and be no where near as strong as the dana.

The only reason to have a 9" is because you can swap rear gears easily with other racers that have them.
The 8 3/4's only advantage is the gear swapping easability.
I would go Dana if I had to get and build one from scratch or if I had one here and needed it.
At this point in time I don't though so I don't. I am only making 400HP so no need for it.

Christian

------------------
Http://ThunderRacing.Knudstrup.net/

68 'Cuda 383 Best of 8.363@83.78 in the 1/8mile which is a mid 12 with a 1.89 60ft
Formula S recreation not original but making like they should have at the factory) Working on adding EFI
69 'Cuda Race Parts Car
76 Duster 273 recent transplant
95 Neon 2.0 SOHC best of 16.96
84 Dodge Ram D50 transplanting 360

[bbaspense]

Not being 'Pro' Phord but if you look under most cars and rails under the 9 second range you will see a 9 inch. If you look under hemi powered SS/AA cars you will see a 9 inch. If you look under a Pro Mod you will see a 9 inch.

If you are going to buy axles and all that why not go to the better housing first. As soon as you say Mopar..the price is always more. The Phord Parts are inexpensive and plentiful.

I have to run an 8 3/4 because my car will be a NHRA class car. Otherwise I would be running a 9 inch and put my extra money left over into the engine.

Jason
indychamp@hotmail.com