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Discussion Starter · #1 ·
Buddy said they did a tech article a little while ago on the old 8's. tried a search but didn't work. How much can these diffs handle power/tq wise? Thanks, Matt.
 

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Depends. They will put up with a lot for a little while. I can tell you that we got 1100~1200 passes out of a set of 8 inch 4.11 Richmond gears on slicks before the pinion gave it up. That's with a 260 HP motor. Since the car will be getting a 400 HP 351C, we will not be going back with the 8 inch.
 

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8" setups are allot stronger then people think. Axles are probably the weakest link.
 

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Buddy blew up four of them. 1 axle tube,1 cap, 1 pinion, and split a detriot locker right down the middle. All of this was done on the street, with street tires. He never did blow an axle though. Mine on the other hand never blew. I was making about 75-100hp more than him.On slicks at the track, too. Kind of a crap shoot. Like a stock block. Not if, when is it going out.
 

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Got a friend running 6.60's 1/8 mile with a 366 Dart stroker, doing it on 28 spline axles. Yet we ate a pinion on an 8" running 8.30s. Depends on what your plan is. I spent $1600 on building a 9 for the Falcon - after 6 years and 1800 or so drag passes, the only maintenance has been to change the wheel bearings this year. All parts look nice and new in there.
 

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I think both are very strong rear ends and as previously mentioned the axles appear to be the weakest point. I have "blown up" both with street (ab)use. I've noticed 8 inch parts are getting harder to find. If I were to be building a car from the ground up I would use a 9 but if you already have a good running car with an 8 I have a hard time justifing the cost of switching to the 9. And for speed, the gears in the 8 are smaller, lighter and not going to suck up as much power (I assume this, I have never weighed them).
 

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Broke the original one in my 65 Mustang on the 2nd or 3rd pass I made at the strip with slicks. Blew the caps off the back.
 

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On 2006-12-11 16:23, XR7Cougar wrote:
And for speed, the gears in the 8 are smaller, lighter and not going to suck up as much power (I assume this, I have never weighed them).
This is 100% true. Buddy lost 2 tenths in the 1/8 when he switched to the 9in. Gear ratio stayed the same.
 

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Discussion Starter · #10 ·
Thanks for the replies. Sounds like for any kind of heavy use the 9 is a safer choice. Anyone know the weight difference?
 

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Depends - with stock housings, the 9" is maybe 30ish lbs more. If you buy an after market housing with thick wall 3" tubes, probably 40~50 lbs. For the stock setup, it's going to be all in the pumpkin - latch onto an 8" center and it's a brick, snatch a 9" center and you'll know right off. I can load an 8" under the car no problem, a 9" center is easier going up on a jack.
 

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All 8" are not the same. The center sections are different. Some like mine are cross bridged in the castings. I run 4:11 Richmond gears with MT's street drag radials. So far 100 passes or so not had any issues.
I make good power as i have broken the forward direct hub in the C4 this yr.
 

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What about for the road racers here? Not as much shock loading, and the light weight may be a bonus. Any word on how they last on the road courses??

Rusty
 

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Actually the pre67 ones are very weak. Just as there is weak 9" models out there to.
 

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On 2006-12-12 13:11, forthman wrote:
All 8" are not the same. The center sections are different. Some like mine are cross bridged in the castings. I run 4:11 Richmond gears with MT's street drag radials. So far 100 passes or so not had any issues.
I make good power as i have broken the forward direct hub in the C4 this yr.
It'll hold up a while, but it WILL go eventually. You'll likely lose the pinion, just like we did. I have no problem trading ET for reliability.
 

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I gave up on the 8" and put a 8.8 in my car. Late model Ford Explorer and Ranger rears are almost the exact width as the orignal rear. I got a 3.73 posi unit with disc brakes from the Junkyard for $375. You have to move the leaf spring mounts, and need a new set of u-bolts and shock plates due to the larger diameter of the 8.8
 

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i had a 302 that made 325hp with an 8'' as so as i sprayed a 125 shot of juice it broke. I shouldnt have done with slicks and a well preped track. good luck!!!
 

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My 8 " has had 500 fly wheel hp motors ahead of it. it keeps in ticking

_________________
1966 Stang Coupe Org. 6 cyl. 351w,Sealed Power Hypers, ARP bolts,Total Seal rings,Eagle H-beams rods,Balanced,Hedman long tubes, Pro Comp 2.05/1.60 Heads, Shaft roller Rockers, Victor Jr intake, Holley 750 DP, Ed Nix Custom .600/.600 254/258 @.050 Solid Cam, Crane solid roller lifters,Richmond 4.11, Strange mini spool, Modified C4, 3500 stall, ******* Transbrake, B&M Hammer shifter, Shelby lowered, Pro Comp 6Al system. Mickey Thompson 275/50 Et Street Drag radials.

<font size=-1>[ This Message was edited by: forthman on 2/28/07 9:48am ]</font>
 
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