bulletproof 8.5 10 bolt or Moser M9???

jayoldschool

3,534 posts · Joined 2001

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#2 · Mar 27, 2012

Your 8.5 will be fine. Save your money. Just about all the big numbers guys still run 8.5s.

 

RatSSled

2,336 posts · Joined 2003

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#3 · Mar 27, 2012

It would be interesting to see if the 8.5" could hold up. I put a Moser 9" with 35 spline axles in mine, which is a similar setup to yours. Another option is to go with a 12 bolt 3rd member for the 9". That would be plenty strong and eat less power than the 9".

Whatever you do, brace the rear. I had the Moser 9" in mine for a couple of years, and it got bent by the power. I had it straightened and added the 9" back brace from Moser. So it would be good to buy it up front.

Also, you should consider 5/8" studs with that much power!

 

HDCAPRICE496 Discussion starter

5 posts · Joined 2012

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#4 · Mar 27, 2012

LOL.... Dammit guys. So I got one for the 10 bolt, one for the 9"/12 bolt hybrid lol!!!! I'm still stuck. Thanks for at least trying to point me in the right direction. I did some searching here before I asked the question, but not too much was definitive... Saw someone talking about the 10 bolt and what it could hold, then I saw a debate between a class racer a bracket racer on the subject and it wasn't really lined out on what a 10 bolt could REALLY handle at our weights... So confused.

Nobody running high HP to a 10 bolt with 30 spline axles, WITHOUT a spool???

 

The Bolt-On Terror

2,393 posts · Joined 2000

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#5 · Mar 27, 2012

In my case it's not been the hp, but how hard the engine/trans/TC/gearing combination hits the tires at the line. and how well your suspension setup can keep that hit from rebounding.
I've broken two 8.5" 4.88 gearsets with only 425 rwhp. Both times have been on a poor starting line where the slicks unloaded after the initial hit then re-grabbed with a lot more wheelspeed in 2nd or 3rd gear and impact loaded the gears. The first time was a minspool failure that also took out the gearset, although that impact was enough to flip a sprag in the tranny as well. The second time was with a Strange full spool.

 

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wagonmasterII

46 posts · Joined 2009

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#6 · Mar 28, 2012

Let's not forget that the nose of the pinion gear is supported in the 9" rear like it is in a 10.5" Corporate14 bolt rear. This just seems like a better design to me and keeps the stresses in the case and pinion gear lower as well. There's a reason the 4 wheelers love the 10.5" 14 bolt . 4 wheeling puts massive loads on axles and I've blown an 8.5" truck axle to pieces with my stock 350 TBI engine. That's when it became time to install the full float 14 bolt in my Blazer. It's just a stronger design, too bad the the 9" has the name Ford associated with it, lol.

 

J

Jeff Green

886 posts · Joined 2004

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#7 · Mar 30, 2012 (Edited)

No debate a 9"Ford is a stronger rearend than a 10 bolt Chevy. If you want to put a rearend that you should never be able to break then it's the 9". But the question becomes do you need that or would ever need that. The ten bolt that is the 8.5 is pretty darn good. But it has limits and even though I run a ten bolt if I tried to leave at full power the car would never move and broken parts would be everywhere.

Now are you going to do that, my money is on NO. You have to have some real power, like over 700HP to have a chance to break a ten bolt that has great parts in it. The weakest link for the ten bolt is ring gear because of it's smaller size. Below is all you need to do to a ten bolt to be good.

1. A quality carrier!! Pay 1000 bucks to get the right one or don't claim the rearend failed.


Thats it!! From what I have seen the factory Impala SS axles hold up and if you don't want to take that chance then swap for Mosers. Add a rear cover plate but again, too many out there without a loading rear cover plate and no issues. Maybe a Moser Pinion Yoke but I used the stock GM yoke to mid 9's at 146MPH in a 4500 pound Impala and it didn't break. The last thing is maybe a Motive gear over the GM, but again not sure it matters, and a solid crush sleeve for anyone trying to get all you can out of them.

I'm not saying the ten bolt is the best rearend, it's not!! But just a few good parts gets 98% of the people on here a rearend they will never break. So the question becomes would your money be better spent on a better transmission and/or other motor or chassis parts??

My 2 cents with a lot of real world trial and error.

 

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wagonmasterII

46 posts · Joined 2009

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#8 · Mar 30, 2012

Excellent reply! No need for Ford parts in our car then !