How strong is an a-body 8.25 and can you make it stronger?

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migsBIG

migsBIG

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So my 73’ duster just happens to sport the big bolt pattern 8.25 rearend. Now I plan to upgrade the engine to most likely a big block with a torque factor of ‘ridiculous’. These are not 8 3/4-Dana 50 rears, so I’m sure their power-to-survival rate is much lower. So my question is, how much power can it take in stock form, and how much can it take with an upgraded truetrac center section and aftermarket axles with an aluminum diff cover?
 
If you can find the diff cover with the set screws that hold the bearing caps, that's one way to add a little strength.
 
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There’s a good amount of post on this if you search 8.25 or 8 1/4. To answer your question though, there’s only one way to find out.

I’m at a tame 430 ft lbs but my tires spin enough to not abuse the rear end too much.
 
I don’t care if you run a Dana 60.
If you abuse it, it’s gonna break.
I’ve allways run 8-3/4 rears and love them. But stuff happened because I got stupid.
Syleng1
 
Cool. I’m thinking if I decide to go big block, I could always sell it and swap in a 8 3/4 or a ford 8.8 rearend. It would just be nice to know what those little guys can take.
 
migsBIG said:
So my 73’ duster just happens to sport the big bolt pattern 8.25 rearend. Now I plan to upgrade the engine to most likely a big block with a torque factor of ‘ridiculous’. These are not 8 3/4-Dana 50 rears, so I’m sure their power-to-survival rate is much lower. So my question is, how much power can it take in stock form, and how much can it take with an upgraded truetrac center section and aftermarket axles with an aluminum diff cover?
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Ridiculous question with that much torque. Just sell it off and get a REAL rear axle in there.
 
As stated, with enough traction, you can destroy any rear axle. We need to know what your final intentions are, street car, race car,
 
If you put sticky tires on and try to make it hook up, then you could have a problem.
 
good golly, people getting excited about a question.

My question was a simple one. Just wondering if there was a hp/torque range for these rearends is all. If they die at 350hp/tq, then say so. I figured it would blow up at real horsepower, but if I can cruise it around before I start going mad scientist on the deivetrain and pop some speed goodies on the small block to make it a bit more fun.

If you don’t know, that’s fine.
 
@Bighead440 used an 8.25 behind a 408? 416? I don't remember for a while and it never broke. He removed it when he did some other upgrades and put something else in it. From the sound of what you plan on, I'd just go straight to a Dana 60.
 
You state “ridiculous torque”. So any money you put into that 8.25 is wasted money. Put it towards a real rear axle
 
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I have had the cross shaft retaining pin shear off on a couple occasions. This would be the sure grip version. I have run them with 340's. I wouldnt even bother with a big block.
 
migsBIG said:
So my 73’ duster just happens to sport the big bolt pattern 8.25 rearend. Now I plan to upgrade the engine to most likely a big block with a torque factor of ‘ridiculous’. These are not 8 3/4-Dana 50 rears, so I’m sure their power-to-survival rate is much lower. So my question is, how much power can it take in stock form, and how much can it take with an upgraded truetrac center section and aftermarket axles with an aluminum diff cover?
Click to expand...

If it helps you any I’m right at 350hp/400tq with fairly soft compound Nitto tires and 3.55 gears 8.25 sure grip.
I twisted off a driveshaft on a stoplight launch once and crossed places where tires repeatedly brake loose and grab again (which makes me cringe because it pretty violent) but no rear problems.
So far :D
 
I ran a Stock Eliminator race car for a number of years
with an 8 1/4. But it was a good one with a spool/Aftermarket
Axles/ and Chryo treated gears. It was 385 Flywheel HP. that
I believe was about the limit of power for reliability for serious racing
It is getting hard to find a selection of gears anymore for it for drag racing.
You might get by with another 50 more Hp on a street cars without a
high stall converter and slicks like the race car.
I talked to Larry Shephard who was the Direct Connection racer liaison
back in the early 70 and he said when Mopar went to the 8 1/4 over the 8 3/4
they saved a whole $2.00 per unit. They discouraged us from using the 8 1/4
for Drag Racing back then!
 
I have a 440 with around 500 hp on a 8.25. They seem ok up till there. Now I did steal a track loc out of a jeep also not sure if that is better or worse. I would be more worried about axel splines actually.
 
413 said:
@rumblefish360 would you care to share your wisdom on these axles, your don’t agree with me so lets hear it.
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What? I don’t agree?

Oh for fucks sake… I had to go back and re read the whole ******* thread again.

Whatever ridiculous torque is, I’d just do a DANA 60 and have a good day. I’ve had 8-1/4 live with over 400 ft/lbs for years. Certainly not a ridiculous amount of torque. After than, hell if I know.

Just WTF is your problem?

O-M-G!!!!!!! Seriously? Un-freakin-believable

Don’t freakin bother me which stupid **** like this!

(Rant edited)
 
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Everything has it’s limits. Weight, sticky tires or street tires. They do make 29 spline axles and crush sleeve eliminators for them. In the end, you may be money ahead in the long run with a 60 if you intend to race
 
rumblefish360 said:
What? I don’t agree?

Oh for fucks sake… I had to go back and re read the whole ******* thread again.

Whatever ridiculous torque is, I’d just do a DANA 60 and have a good day. I’ve had 8-1/4 live with over 400 ft/lbs for years. Certainly not a ridiculous amount of torque. After than, hell if I know.

Just WTF is your problem?

O-M-G!!!!!!! Seriously? Un-freakin-believable

Don’t freakin bother me which stupid **** like this!

(Rant edited)
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You click the red X so explain what you disagree with. don’t click the .X and not explain why. We are all here to learn, well should be anyway.
 
ok. Confirmed with a few racers I know that used these rearends in the 1980's-1990's. general consensus from them was this. Based on launches, heavy vehicles, big tires.
Stock, these could handle 350-400 hp/tq.
upgraded axles, gears and a spool would be good to 450-500 hp/tq before significant flex/carrier failure.
Most said they would upgrade to stronger rearends like 57' Oldsmobile rearend, ford 9in 83/4 and 93/4. Mostly big blocks motor plate applications.
 
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