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PostPosted: Thu Dec 07, 2017 8:24 am 
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Turbo Slant 6
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My road race Dart doesn't make a whole lot of power. I'd guess maybe 175 HP as it sits now, with eventual plans (MPFI, then maybe an Eaton blower) possibly getting it into the 225 range. We already have an 8-1/4" rear with 3.55 gears, and that works pretty well. Adding some form of limited slip is the only upgrade I'd really like to have.

I would've never considered spending the time and money to install an 8-3/4" rear in this car, because I think it would be overkill and extra weight that we don't need. But an old drag racer I know is trying to clean out his garage, and he might give me an incredibly reasonable price on a complete A-body housing and center chunk with sure grip. I would have to buy and install my own gear set, because he says these are worn out; they're also probably a ratio more suited to drag racing. I would also have to convert the axles to big bolt pattern. I'm sure I could resell this stuff for a profit, but I won't. He's only talking about cutting me a deal because he wants to support the racing effort.

So the question is this. If you take out price as a major consideration, is changing out my 8-1/4 for an 8-3/4 a good idea? I don't think our power and torque will ever be too much for the current axle, and I'm not sure the added weight is worth the addition of sure grip. Is there a meaningful difference in durability between these units when it comes to hard cornering? How available and expensive are sure grip units for the 8-1/4"?

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PostPosted: Thu Dec 07, 2017 9:05 am 
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The 8.75" axle is stronger and about the same weight as an 8.25" (within 5-10 lbs). Also, the 8.75" bearings do not have c-clips that can cause you to lose an axle. The sure grip will be a big step up on the road course. Is it a cone or clutch style? I would go for a 3.23 gearset, or maybe 3.55. Doctordiff.com has parts and is great to deal with. You can maybe redrill the 8.75" axles for BBP, or find a used set. Stock C-body axles can be cut and resplined for the right length.

All of this said, I have never used an 8.25" axle and do not know much about quality of SG units. I believe they are reasonably cheap (~$300). I doubt you will blow an 8.25", although our LeMons car has an 8.25" 3.55 SG and it is making noise after a couple of races. We are going to an 8.75" because Jason has all the parts except for a center section, and I have a 3.23 SG center section...

My 2 cents...

Lou

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PostPosted: Thu Dec 07, 2017 10:46 am 
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Turbo Slant 6
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Thanks, Lou! I thought the weight difference was bigger than that. Lack of C-clips is also a big plus. I'll see what he wants for it.

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PostPosted: Thu Dec 07, 2017 12:11 pm 
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Ability to swap pumpkins is also a huge plus (different SG or gear ratio in 2 hrs by yourself). I love the 8.75" axle...

Lou

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PostPosted: Thu Dec 07, 2017 4:44 pm 
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Lack of C-clips is also a big plus.


That is the big motivator... the 8 1/4" sure grip will handle launches like anything else... but hard cornering is like dropping money
on the table in vegas... at some point youll hit a jackpot... except in this case, the tolerance from hammering the clip and axle shaft
side to side will allow the C-clip to fall out, or the end of the axle shaft breaks and the axle shaft take a gainer out the axle housing and
you have some serious reckoning to deal with soon after, and maybe a ride in an ambulance....

If the prices were so high for the 8 3/4", I would have gone that route... but they are spendy now.. and I have been lucky to squirrel
away a couple of 8 1/4" since guys were ditching them for a Dana...

Like Lou said, changing ratios is a big bonus....


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PostPosted: Thu Dec 07, 2017 6:30 pm 
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Quote:
So the question is this. If you take out price as a major consideration


8 3/4

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PostPosted: Fri Dec 08, 2017 4:36 am 
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8.75" every time, if price is not a limiter.

Lou

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PostPosted: Mon Dec 11, 2017 9:22 am 
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Does the 8-3/4" rear have Green bearings installed, or original style tapered bearings?

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PostPosted: Mon Dec 11, 2017 11:43 am 
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Personally, I have no problem with using green bearings for road course duty. I think the main issue is that people left the centering block in the diff and side loaded the bearings excessively, causing failure. I had a vehicle w/greens that was assembled this way and I see how it could mess things up in a hurry. You can also grind the axle length down or add spacers to the bearing plates.

Lou

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