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8.25" weak points #2761158
04/07/20 03:58 PM
04/07/20 03:58 PM
Joined: Feb 2020
Posts: 16
Winnipeg, Manitoba, Canada
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'70Satellite Offline OP
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'70Satellite  Offline OP
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Joined: Feb 2020
Posts: 16
Winnipeg, Manitoba, Canada
So what are the weak points of the corporate axle? To be clear, I still run one if these in my B Body. It has a 3.55 Yukon geared Dura Grip posi in it. I will continue to run it after the 440 is put in. Will I blow it up? Sure. Maybe. At some point. I'm not doing hard launches. It's not a 4 speed car. It's a cruiser. But, eventually, it's on the list to upgrade. For right now, what is the weak point of this diff? I've read countless posts of guys drag racing these, I guess because they are light weight, and not snapping them every run. Some running them for years. So if the unit has a weak spot, what is it and what can be done about it, aside from replacing it with a 8.75" or Dana? Just trying to keep my mind going while sitting at home. Stupid plague.

Last edited by '70Satellite; 04/07/20 04:00 PM.
Re: 8.25" weak points [Re: '70Satellite] #2761167
04/07/20 04:24 PM
04/07/20 04:24 PM
Joined: Jan 2003
Posts: 12,231
md
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mopars4ever Offline
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I have had good luck with the 8 1/4`s that i have but they have been small block (one 4 speed, one auto). I would think it would hold up for a while if you don`t beat on it. No way to really know. Honestly, what do you got to lose if it lets go?

Re: 8.25" weak points [Re: mopars4ever] #2761173
04/07/20 04:35 PM
04/07/20 04:35 PM
Joined: Jan 2003
Posts: 3,102
Auburn WA
Dave_J Offline
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Dave_J  Offline
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Joined: Jan 2003
Posts: 3,102
Auburn WA
The 8 1/4 is the same size carrier as the 8 3/8's in 1,000's of pickups and vans. They are stout enough for most low level hot rodding. So is the 7 1/4 within reason.

My buddy cracked a spider gear on his 8 3/8's but he was stupid doing burn outs by backing up and slamming it into drive or around corners all the time. .


Retired, US ARMY 1973-1994
ASE mechanic, Electrical 1994-1997
Retired GTE/VERIZON/FRONTIER 1997-2015


Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, some may be good.

03 Suzuki Burgman 650(Burger King) Scooter
65 Formula S Cuda
78 Little Red Express Truck
98 Buick Regal (wifes car)
Re: 8.25" weak points [Re: Dave_J] #2761181
04/07/20 04:43 PM
04/07/20 04:43 PM
Joined: Nov 2007
Posts: 20,428
Kirkland, Washington
Pacnorthcuda Offline
Too Many Posts
Pacnorthcuda  Offline
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Posts: 20,428
Kirkland, Washington
In terms of driving, the weak point (for any diff really) is heavy throttle in turns. If you are careful with the throttle in any cornering situation (the tighter the corner the gentler you should be) the diff has a chance of survival.

Re: 8.25" weak points [Re: Pacnorthcuda] #2761189
04/07/20 05:00 PM
04/07/20 05:00 PM
Joined: Oct 2005
Posts: 4,290
WI
Dcuda69 Offline
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Posts: 4,290
WI
I run one with 3:73 gears/factory sure grip in a 470" BB A-body 4 spd. Zero issues. BUT....it's a street car with street tires so those are the fuse. As long as it doesn't hook hard(it can't...lol) it'll live just fine. Different story as soon as you put sticky tires on it....then the fuse moves elsewhere. Good luck!! drive

Re: 8.25" weak points [Re: Dcuda69] #2761207
04/07/20 05:55 PM
04/07/20 05:55 PM
Joined: Jan 2003
Posts: 3,205
Canada -- Posts: 4034 -Registe...
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5thAve Offline
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I've never had problems with any of mine. 7 1/4 on the other hand....

Re: 8.25" weak points [Re: 5thAve] #2761224
04/07/20 07:03 PM
04/07/20 07:03 PM
Joined: May 2019
Posts: 1,227
nowhere
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Sniper Offline
pro stock
Sniper  Offline
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nowhere
I ran one for about 100k miles behind a mild 360 and a 4 speed, SG, with decent meats (255's). Zero issues. Never tried one behind a big block though I did beat on mine when I felt like it.

Re: 8.25" weak points [Re: Sniper] #2761245
04/07/20 08:05 PM
04/07/20 08:05 PM
Joined: Feb 2020
Posts: 16
Winnipeg, Manitoba, Canada
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'70Satellite Offline OP
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Joined: Feb 2020
Posts: 16
Winnipeg, Manitoba, Canada
Well thanks all. That does make me feel better about the situation. Unfortunately, like a lot of other things, my budget for this car, specifically the 440 swap, is feeling the pinch of no work right now because of the current pandemic. The engine should be done by May 1st, but there's the tranny to do, the drive shaft, the cooling system, and whatever else I can't think of right now that just adds to the cost of a swap. But at least knowing that with good quality parts in my 8.25", and some common sense driving, I should be able to hold off on the rear end upgrade for a season or two of taking the wife for ice cream on a Sunday afternoon. Since it was brought up, I am running 255's(BFGTA's). Not that big or sticky. Also, hard acceleration on corners in this big girl isn't really something I'm comfortable with, lol.

Re: 8.25" weak points [Re: '70Satellite] #2761281
04/07/20 09:58 PM
04/07/20 09:58 PM
Joined: Jan 2003
Posts: 7,222
Freeport IL USA
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poorboy Offline
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Freeport IL USA
I had an 8 1/4 with 3:55 limited slip in my 1st street rod, a 35 Dodge 2 door sedan. It had a built small block with a built 904 trans. I beat that thing without mercy.
One day I really got traction and the 8 1/4 paid the price. I'm pretty sure those 2-3 years of previous abuse probably helped with the breakage, it certainly was not because of this one event. The failure was one broken and one bent carrier bearing retaining bolts, which allowed the carrier to shift and took teeth off of both the ring and the pinion gears.When you play as hard as I did back then, you break stuff.
I think your going to be OK, those BFGR tires can't get enough traction to hurt too many parts, just watch your rpms as the tires spin. Gene

Re: 8.25" weak points [Re: poorboy] #2761289
04/07/20 10:11 PM
04/07/20 10:11 PM
Joined: May 2019
Posts: 1,227
nowhere
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Sniper Offline
pro stock
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I almost wonder is the crush sleeve failed and took out the bolts you mentioned. Like the 489 case 8 3/4, the 8 1/4 uses a crush sleeve to maintain preload and, at least in the 489's case, those have been known to crush more allowing mayhem to ensue.

Re: 8.25" weak points [Re: poorboy] #2761290
04/07/20 10:14 PM
04/07/20 10:14 PM
Joined: Jun 2006
Posts: 277
Cincinnati, Ohio
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chargincharles Offline
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Posts: 277
Cincinnati, Ohio
I'm going to agree. I have a 3.55 suregrip that's lived behind my 410 stroker for the last 4 years. It's a cruiser I don't beat on often.
If you just wanna cruise with the occasional burst then you should be just fine. If you plan on EVER going to the strip, upgrade now. Sell your existing set up and find a 8 3/4. Cost of finding and rebuilding now is going to be less than fixing the damage later.

Just my pennies
cc.

Re: 8.25" weak points [Re: chargincharles] #2761624
04/08/20 06:01 PM
04/08/20 06:01 PM
Joined: Jan 2004
Posts: 4,746
fredericksburg,va
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cudaman1969 Offline
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fredericksburg,va
Pretty sure they make the jack bolt cover for the 8-1/4 rear. Then shim the pinion instead of a crush sleeve. Final thing should be c-clip eliminators, break an axel and by by wheel. I’ll find out, I’m putting one in the Duster, 4.30 sure grip and Hoosier radials.


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