8.25 Madness - Power Rating

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racerdude5

racerdude5

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What is the most power you've seen someone put or have put through an 8.25? What's the most extreme abuse you've seen one of these rear ends survive?
 
I'll be interested in the repsonses here, hopefully people will chime in. This is the rear end I have, I plan on shooting for 400 hp, I have heard that they can handle up to that. I'm also wondering if adding a posi makes them more susceptible to breakage.
 
A posi is a limited slip differential. In the case of the sure grip type, it uses a set of clutches and a shaft that when force is applied by the pinion to the ring gear, it presses the clutch packs (outwards towards the axle shafts, squeezing them together against the ends of the carrier) together distributing the power to the wheels. The Auburn gear type uses a conical set up. Others may use springs as well. Does that suffice.
 
Posi is what chevy called their Limited Slip. Its a Sure Grip in Mopar Language.
 
For the original question,,The 8 1/4 should be fine for your 400 hp . We installed a 380 horse Magnum crate engine in a 73 Duster with a 4 speed. Also a 69 Valiant with a heathy 340 automatic. Now don't hate me for using the Chevy word, but it has been compared to the Chevy 10 and 12 bolt as far a being durable.
 
It will take the 400hp level easy. How far it can go is a god question and a hard one to answer since I have seen no one person hit them really hard with power. There is also the issue of track and street useage/abuse.

MoPar's 380 crate engine is know to put out more than 400hp and that is with stock Magnum heads. I have seen racers swap to Edelbrock heads and some have told me that there ported (which is a general description given to me and only that much information is offered up) and there 8-1/4 was in use for several years with that set up.

I know this is not exacting first hand information but it is all that I have discovered.
Life of the rear is shortened by more torque and abuse. Track use is abuse but in low amounts for a short time at a time. The shock of launch appling torque is hard on the rear. Manual trans hit harder.
A manual trans car racer is who you need to speak to about there 8-1/4 's life span and if there is any issues.
 
From what I heard from around the way...

I picked up an 8-1/4 a couple of years ago that I ended up selling before using, but it had a sure grip and ~4.56 gear. The guy ran it in a pretty dang fast drag only 340 Duster. I'm pretty sure they will take plenty of beating.
 
I have one in my Dakota with 4.56 suregrip. The truck has 35 inch tires and the engine is superchiped. 113K miles without issue and the tires spin on a regular basis due to the low gearing. I've had them in other trucks and I would use one. I would have put one in my Dart, but wanted to stay sb and found a 8 3/4.
 
I also run a 8 1/4 in my 360 Dart. It really comes down to how hard the car hooks. If you plan on running slicks you will place a whole lot more stress on that 81/4.
 
I've been running a 4.10 Sure Grip 8 1/4 in my Duster for years and haven't had any issues with it. My 383 would be pulling around 400 h/p or so at the flywheel and it's been raced, gone in burnout comps and get's a lot of street driving and has held up fine.. I'll probably jinx myself now..
 
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