8 1/4 strength

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gilberttitan08

gilberttitan08

Mexican Hillbilly!!!
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Will a 8 1/4 handle a mild 383? What kind of modifications will be required to handle such displacement? Worst case scenario might go with 8 3/4.
 
The 8-1/4 is a pretty tough rearend and it really depends on how well the car hooks up. You can stick a Hemi in front of one and it'll live if the car doesn't hook up. If you think it's going to hook real good the 8-1/4 might have a problem living long term behind a 383
 
Sure it will. There's a couple variables though. Gear ratio is one. Lower gears will throw less of a load on the rear end. Automatics are less abusive And. Tire width comes into play. Also! What car? An A-Body?
A 383 Auto with 3.91 gears and a street tire on an A-Body will last forever. A 383 with 3.21s and a ten inch slick and a four speed in a B-Body isn't the same animal.
 
There's only one way to find out how much an 8 1/4 rear can take... after you hit that threshold then go 8 3/4, or better yet Dana 60
 
The 8.25 is one tough ***** of a rear...and the best thing about them is cost and availability of parts. Every wrecking yard in America is loaded with them. Do some research on the interchangeability of those rears, and you'll be surprised.
 
This is for my 68 barracuda with 4 spd. I believe what I have now is like 2.55 gears or something like that (8 1/4 rear) I gotta double check. I'm not doing slicks or anything massive, just basic tire set up for 15x7's and 15x8's.
 
A "mild" 383 with street tires shouldn't be a huge issue, in my opinion. Now, as far as gearing, it could very well be a 2.41. Not very performance oriented, but the teeth on the low numbered R&P's have a lot of meat on them. Is it a SureGrip?
 
If it was me, I'd probably run what you have for now, and keep a eye out for a solid 8 3/4 that has a gear ratio that will work for you. It may take a little time to find one locally, but with the BB, I wouldn't put the coin in the 8.25 if you want different gears & a sure grip.
 
the pinion stem diameter in an 8 1/4 is 1 5/8" so that is actually larger diameter than the 741 cased 8 3/4 which has a 1 3/8"

I would definitely use it even behind a 383 and I wouldn't hesitate to pound on it either. I have found through personal experience that an 8 1/4 is one tough guy. I have yet to hear of anyone breaking one in real life. You always hear of people breaking them in their car fantasies yet no one ever produces evidence of a broken rear end.

I think the 8 1/4 was an asset to Chrysler and there was good reason they were used so extensively over a long period of time, even Jeep used them.
 
Gilbert, you really could end up with $800/$1000 bucks building a solid 8.25 rear end. If there's any chance of finding a drum to drum 8.75 that's in good condition with a sure grip & 3.23's/3.55's I'd look there first.

Right or wrong, the first thing I look at is under the rear end of cars on display or for sale. To be honest, if I saw a 8.25 under a 68' Cuda BB/4spd, i'd think that cost's were cut on the build and I would wonder where else cost's were cut on the car?

You may plan on keeping it forever, and that would be very cool, but if you ever plan on letting it go somewhere down the road, I'd put my money into finding a 8.75 rearend.....Just my opinion.
 
After you upgrade the 8-1/4 with the sure grip and gears, you'll will still be under a 8-3/4 prove tag. There a good strong rear. They can handle 11's in a big block Duster.
That is where I would yeild. Pressing on could, though I do not know first hand, be a problem. Running 10's in a street trimmed car is demanding on parts. The 4spdnis harder on them vs. an auto trans.

IMO, when you say mild, your not running 11's. Maybe high 12's.
 
it's not the rear you gotta worry about, it would handle a 383 fine

i had a '68 dart with a stout 340 and a 4 speed. it broke the yoke.
 
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