I need advise on an 8 3/4 so I dont break it again

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oldkota

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So two weeks ago at the drag strip I broke my driver side axle shaft and broke a tooth off a spider gear in my auburn cone style posi unit. I wanted to take the cheap and easy way out and get it back on the road to finish the driving season off but I got the wrong spider gears from auburn and am not waiting another two weeks to try another set.

My 8 3/4 is out of an 1970 ebody challenger and has a 489 nodular iron 3rd member. I am thinking I am going to regear so I can run a 28" tire again, and also am thinking on doing a crush sleeve eliminator and upgraded cap bolts.

My main question is what limited slip unit should I get? Ive always like the Detroit trutracs but am being told I'm probably going to break that too. The vehicle weighs 4100lbs with driver, has a 6 speed viper manual transmission and a supercharged 408 with approximately 600hp at the wheels. 95% street driving with drag radials, sees the strip 1-2 times per year with bias ply slicks..
 
heavy car, lot's of power, manual transmission = time for a Dana 60 ???? Might be your cheapest route at the end of the day. Honestly, with that much power and a clutch car and that much weight, a Dana 60 is how you fix a 8.75.
 
318willrun said:
heavy car, lot's of power, manual transmission = time for a Dana 60 ???? Might be your cheapest route at the end of the day. Honestly, with that much power and a clutch car and that much weight, a Dana 60 is how you fix a 8.75.
Click to expand...
That is why the factory installed 60's in the 6 pack and hemi b-body's.
 
Honestly I didn't know I was going to make this much power and wasn't planned for originally, and the 8 3/4 was in before I got it and was hoping it'd last a little while so I could recoupe from the engine build before I upgraded the drivetrain further.. it broke on the first pass I made that I got traction..
 
The way I look at it, a weak link reared it's ugly head. It's cheaper to spend for a dana 60.
or you can wait for the next 8 3/4 failure and do much more expensive damage.
Your money, your choice!
 
My formula chassis ,drive train. engine, tires , paint.
The last one we built yanked the frontend on the first pass, high 9's. lol
 
I know i'm just being lazy now and can research if needed but do you guys know will my willwood disc brakes from my 8 3/4 bolt onto a dana 60?

Either way I don't have money for a dana 60 right this second, maybe ill just try to get it together so I can drive it and take it easier at the track next spring when we go, if I break it then id probably have money again to fix it at that point..lol

Smart? probably not, but id rather be driving on a bandaid then having it on jack stands for 6 months and I'm not worried about breaking it on the street where I do 90% of my driving..

Thanks btw for all the advise.. sometimes I just need to get smacked upside the head a few times before I learn anything haha
 
I like the ease of gear changes with an 8 3/4 but in your case with a 6 speed you dont need that. Just go Dana and dont look back.
Someone had a race dana listed recently IIRC
 
Dana 60 is good advice. But I ran 3 seasons on a 489 case 4.88 gear and never broke it. BUT the difference in my rear was I ran a spool and After market 35 spline axles. 35 spline axles and a Detroit locker will make it live. But then you have compare the costs to going with a Dana.
 
Mopar 8 3/4 Auburn vs Clutch style Sure-Grip. Auburn has 2 spider gears and 1 cross shaft. Clutch style has 4 spiders and the 4 Spider Cross Shaft, much stronger.

If you can keep the differential in tack then it probably won't break the axle either.


4spider.jpeg
 
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