Tell me how strong was or is you 7 1/4 rear.

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Confusedcuda

Confusedcuda

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Just curious, are they as weak as some say? Tell me your findings with the 7 1/4 rear end...
 
Confusedcuda said:
Just curious, are they as weak as some say? Tell me your findings with the 7 1/4 rear end...
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I ran mine with a 340 in my 65 Cuda with a 4 speed. I had those crhome ladder bars on it and it handled the power ok. I had little 60 series 14's, but then I tried a narrow little slick and she broke good. We couln't even push her off the track it had to be towed. Now the 65 has a 8 3/4 from a 69 Dart.
 
Don't try to do any brake stand burnouts or you'll hear a sudden "SNAP"!

Don't make a 90* turn and pour the power to it in the turn. Yep "SNAP"!

Having given these warnings, the one I just pulled out of my 66 has been in there behind a hot 360 / 727 combo for about 15 or more years now. And it's still good to go, even with the 2.94 (?) gears. I drove that sucker pretty hard, but always made sure I was level and straight before putting the go pedal to the metal. :)
 
I read that the 7 1/4 was junk(weak), specially when compared to the 8 1/4 or the strongest 8 3/4. It can handle abuse from a six but if you change engines, change it, or take it easy! Like said previously, it won't handle slicks. But on the good side, they even came from the factory behind a V8, on the last year they made the Cordoba.
 
mine lasted 6 months behind a stock 360 4bbl and a 4 speed in my '63 Dart including some burnouts altho that was on 20+ year old 5.60x13 bias plies...

broke a big chunk off the crown wheel when push starting the car one day and swapped in an 8.25 - no problems since.
 
J.G., you're right. When compared to the 8.25" or 8.75", the 7.25" is definitely the weaker of the three. That's why I have a complete 8.75" ready to go into the Vart this time around. I figure I pushed my luck long enough with the old, weak, but reliable 7.25". :)
 
for all you people who said it went "snap", where exactly did it go "snap".
just curious.
 
Spider gears tend to blow apart in the 7 1/4. They fly sometimes to, right thru the cover. But you can have fun with one before you yank it and turn it into a Lincoln or Miller Locker.
 
I've never broken one, but I've also never had one behind anything but a stock /6 with skinny tires or a tired 318.
 
I had one behind the stock 273 2 barrel with a 4 speed & about 9" wide tread 60 series bias ply tires. I broke teeth off a spider gear on a hard shift into 2nd gear. It took some abuse from me beforehand, but I don't remember for how long. Probably about a year. I also think somebody had been into the rear, before I bought the car, to fix a problem.
 
I never found out, took it straight to the scrap yard, was probably recycled into a Honda!
 
I had a 7 1/4 in a stock '86 Gran Fury driving down the road after a hard lunch one day "snap".On the dissection,I found that not only did the Differential pinion shaft break,I split the Differential itself in half.Along with a few Pinion gear teeth.
 
Its probably ok to run one behind a slant or 318 they are'nt making enough power to break one,but if your going to run a 340/360 i would;nt trust a 7 1/4 behind one go 8 3/4...
 
on a 74 duster leaning tower of power we let the right tire roast and snap there she went. how we got it to spin I don't know I think it had something to do with a lot of beer...
 
340srule said:
None that i've ever seen..they're call "boat anchors" for a reason..lol...
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I destroyed 2, 7 1/4's, with a stock 1977 2 barrel 318 in a "Roadrunner" of the same vintage. The last one was a SureGrip. Did all this carnage on E-70x14 Goodyear Polyglas rim protectors. The first one went snap pulling out of a gas station and turning right. The second one went snap when I found myself going backwards at 60MPH, after hitting a foot of water in the road that I didn't see in the dark, and I floored it. On the other hand, I've seen 7 1/4's live forever with the right gears. The break seems to be around 3.55. I have a 3.55 in my '66 Valiant that is showing no signs of distress, and Dad pulled a 25' travel trailer using a slant powered '67 Valiant with 3.91's for years. I'm guessing the smaller pinion gear on the lower numerical ratios puts too much side load on the carrier and they split. If you want your 7 1/4" to live, lose the highway gears. Just my $.02.
 
Boat anchors... That's funny. There are few 318's around here that would put a hurting on lots of 400+ ci stroker motors.

Bob Mazzolini has one of them.

There are plenty on /6 and 318's that could torch a 7 1/4.
 
my 7 1/4" withstood about 3 months of daily driving and weekend abuse behind a 250hp 360 before it went bang. it was the spider gears that went. however, upon later removal of the trans, i found that the snout of the torque converter was cracked in two places!!! front to back!!! so make sure if you break anything in the rear end that you check out other elements of the driveline to be safe unless you are absolutely sure your parts are bulletproof. i made 6 dyno pulls to 5000+ rpm on that converter, that really could have been a disaster - think flying shrapnel and missing body parts. i'm thankful to be so lucky that nothing happened.
-tim
 
I beat the hell outta my 7 1/4 SBP rear and never did break the thing. I used to run the car up to 100mph on the ice, do neutral drops and that was before I swapped the 360 into it. Then I took it to the drags about 2 times a month not to mention the street beating it got. I used to power brake that poor thing all the time. I am definately surprised it never popped. I finally swapped it out for another one only because I was planning a cross country trip and needed more apprpriate gears. That rear didnt see but several hundred miles before I swapped it out for the 8 3/4 sure grip I have now.
Hmmm guess it just depends on how lucky you are?
 
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