What can a 7 1/4 rear take???

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aprfct0 said:
Not to barge into this thread but has anybody ever "spooled" their 7.25 and what were the results when you did? I've heard of a lot of off road guys doing this not sure how it would turn out on a street car.
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I've heard of them snapping/twisting axles in street cars. maybe something big and strong and you would be okay but I think you would twist or snap a 7 1/4 axle.
 
I have an open 2.76 ratio 7.25" behind my stock/tired 318/auto...and I was never kind to it but not outright abusive either It did eventually break in the middle of a power-brake on one of the local roads famous for having slippery pavement. Sure enough, the carrier cracked.

I had it repaired to get the car back on the road but I would have been smart to put the money towards a 8.25" (which I'm now searching high and low for).
 
I guess I will just have to go easy on it. That won't be too hard because I intend on street driving and cruising mainly.

Mrgtx did you pay a lot to fix that 7.25?
 
71swanger said:
I guess I will just have to go easy on it. That won't be too hard because I intend on street driving and cruising mainly.

Mrgtx did you pay a lot to fix that 7.25?
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Yessir...the local rear axle guy (and that's really all he does!) charged $350ish to put it all back together. That hurt at the time...lesson learned.
 
When i was in H.S. I had a '70 Charger, I took the 318 out and put a 440 in it, that only had a 7 1/4 and I ran it like that for about a year till I could afford an 8 3/4.
I wasn't easy on that rear either.
 
Wow a 440 on a 7 1/4? That must have been hard not to blow that rear end out for that year. That gives me more hope for my little 7.25. Like I said, I am not going to race or hot rod the car. I just want a nice driver that will last the test of time. Maybe down the road ill look for an 8.75, but for now I'd like to stay with what I have.

Mrgtx after you had the 7.25 rebuilt/fixed how does the car run? To clarify, does the rear end work as it did before, or do you think it can take more abuse because of being freshly built?
 
I destroyed at least 4, maybe 5, 7 1/4's when I was young behind a 170 slant six, three on the tree. Also a turbo 400 behind a 396.
 
I am running a 7 1/4 behind my 360 727 with no problems. The motor is your standard 360 build. good cam, rpm intake, 650 cfm, headers, and ignition. I am HARD on that rear end and it has still not failed me. I have a 8 1/4 in my garage so I have really been beating it recently and it still will not break. By beating it I mean every time I drive it I am power braking it and kicking it sideways around every left hand turn I come up to. I think you will be fine as long as you keep it straight and dont hook up. As long as the tires are spinning its not going to be THAT tough on the rear.
 
I launched schap metal thru the rear cover on a slant six 73 dart (parts car at the time) doing some burnouts with it, haha. The ring and pinion were fine, but the spider gears and diff pin were another story.
 
ive had good luck sofar with mine, its also a limited slip 2.91 setup being pushed by a stock 87 gran fury highway patrol 318 and lockup 904. few burnouts here and there. Sofar all is well! ill be getting rid of it here soon for an 8.25 setup however, just because and i can, and id rather do it now then when i HAVE to....
 
i had a 7.25 in a dart with a 273 and a 318, 904 auto i really tested the crap outta it it never gave me any problems. both engines were stock 2bbls. kinda give you a idea i was 18 at the time
 
Dang! A lot of folks sure have tested these little rears. That's crazy that some people blow the rear right away and others can beat the for a while and not break em. I guess it's luck of the draw. I know a local guy who sells the 7.25 and 8.25 rears for about $200 so worst case scenario I can alwas replace mine if it blows up
 
The 7 1/4 is not as bad as some make it out to be. As others have said, the best thing for a 7 1/4 is a SG unit. But they are hard to find, and repair parts are even harder to find. There were two different type Sure Grips. Early clutch type, with 4 spider gears, and the later cone type with only 2 spider gears. The clutch type is the best. I have three 7 1/4 rears. A 5.13 SG, a 4.56 SG, and a 3.91 SG. The 3.91, I have been running since 1974 in my slant six cars (been in 4 of them). Just pulled it out in 2012, when the SG started slipping, and installed a 8 3/4. This rear has withstood thousands of 1/4 mile passes on slicks, in a 3200 lb car. The car 60 foots at 1.79, and runs 13.2's at about 100 mph. The engine makes 358 foot lbs torque at 2900 rpm.

All of that said, I don't reccommend the 7 1/4 unless you already have a good one. It is next to impossible to find a good one used, at this late date. Just as hard to find parts to repair it properly, particuly the SG unit. There are better options.
 
I have a stupid question. Could I put 323 gears into a 7.25 rear? What makes the gears compatable or incomparable?
 
You can put any 7 1/4 gear in a 7 1/4 rear, and yes there is a 3.23 ring gear. If you are asking what I think you are asking gears are not interchangeable unless they are from the same size rear end, meaning an 8 1/4 ring gear is not comparable with a 7 1/4.
 
I'll start of by saying - I don't know anything about the smaller diff but I used to do a fair bit of drag racing with other brand cars with small diffs.
If you want the little diff and want it to last - AUTO trans, just be easy with the shift kit, if you have decent power/torque you may want to think about heat treating your axels & gears (did this with my R100 Rotary back in the 80's - it works). The reliability is all in your right foot, push it hard and you may be pushing your luck also. Sometimes it's cheaper to swollow your pride a little, spend the $$$ on a stronger setup and then have the knowledge that your going to be driving home, not paying someone to bring it home for you....then you still have to fix it. IMO
 
One of the Darts I had years ago had one when I put a 360 in it. Took me a whole half a day and it exploded. To get you by while you are saving the $$ for something else is fine, but why throw $$ at something that is just weak?? If you are talking about just a putt putt car then sure but.....
 
Unfortunately, I am one of THOSE people! And I just spent damn near 3 grand on a rebuilt 8.75. That's drum to drum, & did include spring relocation and the hardware to upgrade from the 7.25 and that kinda lessened the bite. The funniest part is that it's going behind a stock /6! I'm planning ahead for the hot small block in the future.

ATB

BC
 
64ragtop said:
Unfortunately, I am one of THOSE people! And I just spent damn near 3 grand on a rebuilt 8.75. That's drum to drum, & did include spring relocation and the hardware to upgrade from the 7.25 and that kinda lessened the bite. The funniest part is that it's going behind a stock /6! I'm planning ahead for the hot small block in the future.

ATB

BC
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You know if you want a non DIY rebuilt a-body 8.75, your gonna pay for it, it also depends on what kind of resto your doing. Hope you get that back out if you sell it.

That is pricey though, damn near a cautionary tale: don't get caught up in brand, no one manufacturer has all the answers.
 
I'm very sure that no one maker ever had all the answers, but there's a little twitch in my tear ducts when I hear of ford and gm parts as improvements to a MOPAR.

WHOA!! I didn't say that they absolutely would not be an improvement, just that little tingle. Chrysler was always #3 in the Detroit "Big 3" automakers, made fewer cars, have fewer survivors and so on. But I grew up on Plymouths, strayed for a while, but found my way back to the old love affair. Like I always say when someone builds one differently than I would, Your car, your money, your choices!

P.S. I probably killed its resale value having it narrowed and set up with spring relocation. But it'll let me put fatter rubber in the ragtop's itty bitty rear wheelwells.

ATB

BC
 
64ragtop said:
but there's a little twitch in my tear ducts when I hear of ford and gm parts as improvements to a MOPAR.
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Sometimes it is not about an improvement.....it is just because Mopar does not have something that will work or is just flat out less money. I am planning on at the minimum a stroked 400......and I want an OD with a lock up convertor.......and the ability to have the trans shift softly when just putting yet get aggressive when the go pedal is mashed on..and have a whole different program for track day.......which leaves out pretty much anything Mopar made........and there aint no way I would have dropped 3k on a rebuilt rear end.......I have a grand total of $75 in the brand new rear housing....a Currie 9+ center case, donated from Dougs Performance Transmission in AZ and some axle tubing from Moser.......
 
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