LWB driveshaft question

[Turbo4whl]

GM 12 bolt uses spiral bevel gears.

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Old Ford 9", unless it has been modified, has hypoid gears.

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The Ford 9" offers quick gear ratio swaps many old time drag racers like. Pull the axles on the 9", swap the carrier with one already setup with a different ratio. While the GM housing requires timely gear ratio swaps. So, unless the Ford 9" carrier has been modified to use the spiral bevel gear set, the GM spiral bevel gear offers more tooth area contact and less horsepower to turn it. The integral GM housing, stronger and lighter.

I am a seasoned mechanic with many third member overhauls, from Chevettes to HD 30-ton trucks. Also fixed many that have been set up wrong the first time, by inexperienced mechanics.

Just my 2 cents...

 

[82SquareBurb]

it will need to be shortened the centerline on the 9" (axle to center of yoke) is longer due to design differences.

Thanks for the info David! Yeah the yoke stuff caused some delays even with the stock 10-bolt.

I figured this won't be the last final length, (are they ever really done? lol) and hoping to do the swap in concert with a static drop since that may change it again. My driveline guy said they can just cut/re-weld when the time comes.

I like your suspension setup! I think my leafs are super saggy on this rig, may need to address that down the line along with some traction aids. Pretty much copying you at this point

 

[82SquareBurb]

@Turbo4whl that is interesting! saw a video by Uncle Tony on that topic. I looked at the 9" just for availability, I have searched for a (local) 12 bolt, no luck so far. If you know where there might be drop in ready 12 bolt with all the fixings to put behind (700-1200HP) boosted setup that will live in a 5000 pound truck, pass it on. I am in the market for a new rear with disc brakes.

 

[xm20k]

Stock same gears and setup to fit the same vehicle the 12 bolt is 30lbs lighter than the 9" with a nodular iron center and uses 2-3% less power to turn.

Street usage at 500-600HP it's a wash.

However, when you go to a race build with thru bolt big bearing aluminum center, spool, 40 spline axles, drive hubs, etc. the weight becomes a non-issue as the 9" will take 2000+ HP

The 12 bolt can only handle about 1200 with proper prep, reinforced welds and bracing, 35 spline axles, c clip eliminators, or 9" tube ends with custom axles with press on bearings. They have no were near the aftermarket support as the 9" when going big power. At this point people are either going Dana 60 or bigger or 9"

Mine is setup with a 4.56 on a billet spool in a nodular iron center with 31 spline axles no extra beef and if I decide to make more than the current 615hp I'll just drop a big bearing center in the back braced one I have with 40 spline axles and ladder bars and swap that in.

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[Turbo4whl]

@Turbo4whl that is interesting! saw a video by Uncle Tony on that topic. I looked at the 9" just for availability, I have searched for a (local) 12 bolt, no luck so far. If you know where there might be drop in ready 12 bolt with all the fixings to put behind (700-1200HP) boosted setup that will live in a 5000 pound truck, pass it on. I am in the market for a new rear with disc brakes.

You might find what you want at Carlisle this weekend.

 

[Turbo4whl]

Stock same gears and setup to fit the same vehicle the 12 bolt is 30lbs lighter than the 9" with a nodular iron center and uses 2-3% less power to turn.

Street usage at 500-600HP it's a wash.

However, when you go to a race build with thru bolt big bearing aluminum center, spool, 40 spline axles, drive hubs, etc. the weight becomes a non-issue as the 9" will take 2000+ HP

The 12 bolt can only handle about 1200 with proper prep, reinforced welds and bracing, 35 spline axles, c clip eliminators, or 9" tube ends with custom axles with press on bearings. They have no were near the aftermarket support as the 9" when going big power. At this point people are either going Dana 60 or bigger or 9"

Mine is setup with a 4.56 on a billet spool in a nodular iron center with 31 spline axles no extra beef and if I decide to make more than the current 615hp I'll just drop a big bearing center in the back braced one I have with 40 spline axles and ladder bars and swap that in.

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You are right, way more aftermarket available to build the 9 inch. Me I just run my truck 10 and 12 bolts. Aftermarket gear set behind the modified 700R4 and 402 BB torque engine. The 700R4 breaks first, I keep a spare.

 

[Rustisbest]

Since we're comparing them and they havent been mentioned already, the 9" has the tail bearing support on the pinion like GMs 14 bolt which makes them stronger.
10 and 12 bolts have c clip axles where the 9" axles are has bolt on axle retainer plates. C clip eliminators are made for the 10/12 bolt but unless something has changed recently they leak.
9" is much easier to set up with spanners on each side of the diff instead of shims.
What I did for budget discs on mine was bolt on brakes from a 96 and up Explorer with the 8.8. $100 for a complete axle and got some of that back when I scrapped the 10 bolt and leftover 8.8 stuff. Internal parking brake was easy to hook up using the factory cables. Just changed the cable ends out using clevis' that Wilwood makes.

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