7 1/4 rearend

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Scampin

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So I know its weak. But how weak? Will it withstand a few trips to the track? Got a 64 barracuda, 273 4spd w/ 2.96 posi rear end. Plan on either playing around some with the 273 or upgrading to a 318, nothing radical, probably wont go over 250-275hp. Plan on using old belted street tires. Would like it to be in the 14's.
So... will it last?
 
Put either a 8.25 or 8.75 or Dana 60. Otherwise you'll be that guy at the track when you're 7.25 blew up. If your itchin to blow up it up just do a hard launch/burnout in front of you're home. That way you just have to push it up the driveway.
 
They failed behind stock slant sixes.
 
my 72 duster has its original 7.25 that had a 318 nd a 4spd infront of it which now it has a older 318 and a rebuilt 727 with a small shift kit in it now ever since ive bought the car ive tried to roast the tires and ive done some hard launches and its still going
 
i had one added 410 gears to it and beat the tar out of it and it woildnt break just makemsure u put a street tire because sticky tiremwill kill it..and itmwas behind a 509 cammed 360
 
bignasty123 said:
i had one added 410 gears to it and beat the tar out of it and it woildnt break just makemsure u put a street tire because sticky tiremwill kill it..and itmwas behind a 509 cammed 360
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7-1/4" or 8-1/4"? I have never heard of 4.10 gears being available for the 7-1/4"?
 
No. My 7 1/4 didn't even last one trip around the block behind my nearly stock 318/904 back in high school. My friend turned a corner, goosed it and busted the spider gears. Luckily we were only 100 yards from his house.

I think it would be even easier to break with a 4 speed.
 
I had one in my car for a few months. After reading a little my opinion is this: if it sticks, it will blow.

So unless you have bald tires, buy a new axle. 8 1/4's(which i have) are dirt cheap, and very easy to swap in.
 
ramman7284 said:
my 72 duster has its original 7.25 that had a 318 nd a 4spd infront of it which now it has a older 318 and a rebuilt 727 with a small shift kit in it now ever since ive bought the car ive tried to roast the tires and ive done some hard launches and its still going
Click to expand...

One of these days don't be alarmed when you hear the fatal "Bang".
 
The poor little 7-1/4 breaks behind slant sixes if you get one wheel spinning. (like on a little bit of ice around a corner and then it grabs some traction) I've gone through 7 of the one leggers on various cars. I'd just replace a 7-1/4 with a 7-/14 because they were $20 at the local yard. I still have a 7-1/4 sure grip that is intact in one of my Barracudas but I would really recommend that you pull that 7-1/4 and sell it to someone restoring a slant six car and upgrade to at least an 8-1/4 with your combo. The sorry 7-1/4s are no match for any sort of performance improvements.
 
I have 2 A-body 8.75's in my garage now. Not for sale, but I'd consider trading the one that needs attention for an 8.25 that's ready to go, give or take. So, they are out there, pricier, but worth it for the added peace of mind and durability.
 
Maybe I'm an exception to the rule but I ran a 7 1/4 posi in my '67 Cuda on the street behind a mild 318/727 & later behind a strong 360 until I got an 8 3/4 & never had any problems. I'm not recommending it - just sayin'.

Now running a Dana 60/ 4:88s behind a RB!
 
ive ran a 7 1/4 one wheel wonder behind a 360/727 with some 275/60/15s and it would light it up no problem, never broke. though i wouldnt recommend trying to do burnouts with these things, but for normal use , ive never seen one let go.
 
the 7 1/4's poor rep. is exaggerated for daily use & occasional spirited driving on the street but would recommend upgrade if you ever go to track. Like grimreaper said spinning to traction kills these poor little guys. Made the mistake of getting aggressive at a test & tune instead of walking off of line in previous pass trying to get better time in my 65 valiant & that's all it took to get it to puke instantly and this was with sturdier 7 1/4 sure grip.
 
I have a brand new dana 60 sitting under my 71 scamp. That hasn't moved in 8yrs. I guess if the 7 1/4 pukes I can throw that in? Will that bolt into a 64?
 
richmond gears sell 411 s for 150 bucks look at the website and i beat the tar out of it and welded the spider gears and made a poormans posi much fun
 
I had one in my ex-wifes daily driver duster.
3.23 open rear with 235-60-14 tires, the car would never hook up just spin.
My ex wife had a lead foot so it went thru alot of motors with a 4-speed.
She blowed up the original slant with 70K on it this was in about 1987.
She then proceded to blowed up at least 3 more small blocks in 10 year span in the same car.
The rear never broke because it would not hook up...... or I was just lucky
 
Man, I feel lucky after reading some of these 7.25 horror stories.

I used to burn the crap out of my tires back in the day with my Duster which had a 318/904/7.25. Never once did I have a problem with that rear end. The wheel bearings did go out on one side once, but that was an easy fix. I also raced it at the track probably a half dozen times, including burnouts before lining up at the tree. I also did plenty of burnouts off the track as well. I did upgrade the intake, cam, and carburetor (600 cfm eddie), the little guy still seemed to do fine. Mine did get posi when I burned out, so I'm guessing I had some kind of limited slip going on back there. I have never done a burnout in my Dart, and I don't plan on it. I'm 10 years older and a bit wiser I guess.

Maybe I just had an extremely well built unit, that and the previous owner, my Dad, took excellent care of that car.
 
bignasty123 said:
richmond gears sell 411 s for 150 bucks look at the website and i beat the tar out of it and welded the spider gears and made a poormans posi much fun
Click to expand...


Not being a prick, but on their website, 8.25" is the smallest R&P set I see listed.
 
I've done some pretty good burnouts with the barracuda and it has held up so far. I wonder what the record for the fastest pass with a 7 1/4 is?
 
I've had 2 failures...
Neither what your talking about though.
One, a hundred miles from home, the yoke fell off... As in the nut...As in PO musta had a new seal installed and yoke wasn't properly tightened. Got it reassembled but only about15-20 ft/lbs tight with the channelocks in my tool kit I had with me...Used a centerpunch to bugger the threads so it wouldn't come off 'til I got to a gas station. It's a Sunday...The bonehead working says "bring it in, I'll tighten it up and refill the oil" , then proceeds with Ingersoll-Rand to try and pull the pinion all the way through the yoke.
I shoulda just had him add oil...
It was smoked by the time I got home...

I also would NOT jack a car with a 7 1/4 up by placing the jack under the rear(Diff). The junkyard replacement had an axle tube break loose from the center section...:eek:ops:

It wasn't the V8 and burnouts I had trouble with...:burnout:
 
Weakest link,,,Ya might get 5 or 20 passes out of a 7.25.Then again I have been down the strip 5 times at Vegas and drove the car there and back from LA.butt it was aluminum block slant six and only ran high 17s.I was worried more about my aluminun block than my rear end.
 
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