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11/02/2020 9:45 AM  #1


Axle housing 8” or 9”

What advantage(s) is there to having non tapered outer ends?
Or disadvantages?

Obviously concourse is of no concern to me.

This would be with any small block only. (260-351w stock as well as stroked)

Last edited by Nos681 (11/02/2020 9:46 AM)


Dan - A9L/5.0/T5/3.25 Currie 8” TL/2016 Mustang GT brakes - I’m further north than some Canadians.
 

11/02/2020 10:12 AM  #2


Re: Axle housing 8” or 9”

Tapered ends make your ride height a little higher...  Lighter weight.  Use original u-bolts and shock plates.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

11/02/2020 10:46 AM  #3


Re: Axle housing 8” or 9”

For our application there's no strength advantage or disadvantage to the housing itself.  The 9" center section is stronger, and has an unlimited amount of options for differentials, gears, axles, and cases for everything from stock to 6 second door car.  On the street you should be able to find a decent street gear set for the 8" and there are a few differentials that are good choices out there.  With street tires you shouldn't be able to shock load it enough to break it; the tires will just spin. 

 

11/02/2020 4:40 PM  #4


Re: Axle housing 8” or 9”

One other thing to consider is if you have a banjo style housing or not.  The banjo style housing is weaker but offers better clearance for exhaust. 

 

11/02/2020 9:03 PM  #5


Re: Axle housing 8” or 9”

what horse power does it take to turn each one?
 

 

11/02/2020 10:51 PM  #6


Re: Axle housing 8” or 9”

TKOPerformance wrote:

On the street you should be able to find a decent street gear set for the 8" and there are a few differentials that are good choices out there. With street tires you shouldn't be able to shock load it enough to break it; the tires will just spin. 

Tell that to my brother with a 289 with 3.89 gears and an untimely side step of the clutch

Last edited by Bearing Bob (11/02/2020 10:53 PM)


Bob. 69 Mach 1, 393W, SMOD Toploader, Armstrong  steering.
 

11/03/2020 6:03 AM  #7


Re: Axle housing 8” or 9”

Bearing Bob wrote:

TKOPerformance wrote:

On the street you should be able to find a decent street gear set for the 8" and there are a few differentials that are good choices out there. With street tires you shouldn't be able to shock load it enough to break it; the tires will just spin. 

Tell that to my brother with a 289 with 3.89 gears and an untimely side step of the clutch

Key word there was "shouldn't".  I didn't say "can't".  I've seen all kinds of rears, transmissions, etc. broken with power levels that shouldn't have been able to break them, but enough abuse can break anything.

There's a couple things to keep in mind with 8" and 9" rears.  The 9" is touted as being so strong, almost mythically unbreakable.  I'm here to tell you that's a crock.  The run of the mill 9" break all the time under hard use.  That unbreakable reputation was built on a handful of N case rears that had Detroit lockers in them from the factory. 

The inherent design of the 8" and 9" has a flaw.  The pinion bearings are too close together.  This necessitates the pocket bearing to support the pinion head.  The problem is that they put a crush collar in the mix.  Those crush collars do not remain static length under shock loads; they oscillate.  That often translates into a huge load on the pocket bearing, and blam!  I've seen dozens of 9" cases with the pocket bearing bore fractured, and at that point basically the whole center section was junk except maybe the diff.  Using a solid spacer instead of a crush sleeve greatly improves strength and durability.  Its one of the reasons Dana rears are so highly regarded.  Most if not all use solid spacers from the factory, making even puny rears like the D30 and D44 pretty hard to break.

Some 8" rears also had diffs that only had 3 pinions, and those for obvious reasons are pretty weak as well.  There are 4 pinion ones available though, and those should be considered mandatory if you're going to hammer on it. 
 

 

11/03/2020 6:11 AM  #8


Re: Axle housing 8” or 9”

val fulesday wrote:

what horse power does it take to turn each one?
 

The difference is pretty negligible between an 8" and a 9".  The basic design is inherently less efficient than say a Chevy 10 or 12 bolt due to where the pinion connects with the ring gear, but even this difference is marginal.  Strong transmissions, rears, etc. all soak up power.  Its just a fact of life.  A lot of those super tough automatics can absorb 25% or flywheel HP.  Its why I believe in matching the drivetrain to the intended use.  An overbuilt drivetrain behind a mouse of an engine tends to be a lackluster setup, unless the future plans call for more power, in which case you're just super smart. 

 

11/04/2020 6:50 AM  #9


Re: Axle housing 8” or 9”

the 8" rear end i bought has a carrier the is cross webbed, like little boxes, the carrier that came out of the 8" in my falcon just had lines the run across it. in handling both of them i noticed a significant difference in weight. is the cross webbed really that much better an alternative for strength? i am taking the 3.80 gears out of the auburn unit and putting in the 3.25. out here in west texas, i like the idea of being able to drive the car to car shows. my theory is if it's on a trailer it's because it's broke.

 

 

11/04/2020 7:31 AM  #10


Re: Axle housing 8” or 9”

The early 8" housings only had the horizontal ribs. On '67 and later 8" housings Ford added the vertical ribs which created the "little boxes". The later housing is the only way to go if you have a performance engine.

 

11/04/2020 4:11 PM  #11


Re: Axle housing 8” or 9”

You will see the same pattern on all modern transmission cases and even engine blocks.  The webbing allows them to remove weight that doesn't add to strength, while keeping the casing very strong.  One of the first manual transmissions that was built like this was the T5. 

 

Board footera


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