1BadDodge71
FABO Rice Hater
Ive been wondering what exactly makes the 7 1/4 such a weak rear end and why no one has figured out a way to strengthen it or beef it up instead of scrapping them:read2:.Is it the gears inside that are weak?Your thoughts?
7 1/4 Why is it so weak?
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pettybludart
Well-Known Member
The axels weren,t built for torque or HP.It,s like a CV joint,add some power and snap,seen it happen too many times at the track.Buddy breaking CV joint in daddys car,good luck explaining that to daddy.
C130 Chief
Mechanical Genius
Physical size of all parts concerned. Cheapest and easiest way to beef up is swap to something else.
The Cheif nailed it and good. While it is possible to strengthen the parts through cryogenics, the cost factor vs strength gain is not worth the effort. The actual part size is very small for the power given to it. Small V8 power will usally destroy it in a short time.
The 1 inch larger rear (8-1/4) is fine for 400+ HP behind a mild big block like a 383 or 400. A 440 will be OK if you leave the power plant alone. It makes enuff torque to kill it if you hammer it alot.
I've seen 500 Indy headed big blocks dish out some really low 9 second runs with an 8-3/4. Only a 1/2 bigger then the 8-1/4. Capable of much more power.
Both of the 8+ sized rears are easy to get with the 8-1/4 being preety cheap. A new sure grip unit is under$500 IIRC for the 8-1/4. Easy up grade.
The 1 inch larger rear (8-1/4) is fine for 400+ HP behind a mild big block like a 383 or 400. A 440 will be OK if you leave the power plant alone. It makes enuff torque to kill it if you hammer it alot.
I've seen 500 Indy headed big blocks dish out some really low 9 second runs with an 8-3/4. Only a 1/2 bigger then the 8-1/4. Capable of much more power.
Both of the 8+ sized rears are easy to get with the 8-1/4 being preety cheap. A new sure grip unit is under$500 IIRC for the 8-1/4. Easy up grade.
Believe it or not Mopar offered a sure grip for the 7.25 axle.
Grinder
Banned
Yes and it added considerable strength to it.
pastortom1
Well-Known Member
If this is true, I think it would be great to have some elaboration on the units that might be available, to help the guys who can't afford to buy then swap out a full rearend....not all the guys can do it themselves, not all the guys can afford to pay a shop to do it (or buy all the parts and essentials and extras needed), and not all the guys have friends to help them with their projects.
IF the sure grip is available for the 7-1/4, and IF it will strengthen the whole unit (I assume by spreading the load evenly, thus reducing the pressure on the weakest points), then LET'S HAVE SOME DETAILS AND INFO.
Might save a bunch of guys some real costly and aggravating headaches. No? :read2:
IF the sure grip is available for the 7-1/4, and IF it will strengthen the whole unit (I assume by spreading the load evenly, thus reducing the pressure on the weakest points), then LET'S HAVE SOME DETAILS AND INFO.
Might save a bunch of guys some real costly and aggravating headaches. No? :read2:
Guitar Jones
aka Angry Johnny
Parts are scarce for one thing, aftermarket gears or axles, etc are pretty much non existent. It's just not worth the effort to mess with. There are more than a few tech threads about 8.8 Ford rearends which are probably the best bang for the buck as the A body 8.75 housings are pretty expensive. It's almost cheaper to get a B or C body 8.75 and have it shortened.
caferacerx
BAND MEMBER
the labor and expense to put a sure grip in a 7 1/4 would far exceed that involved in a simple and cheap 8 1/4 swap
pastortom1
Well-Known Member
Does anybody know what cars would have been offered with the 7-1/4 sure grip in the first place? This is the first I've ever heard of it even being in existence. :read2:
caferacerx
BAND MEMBER
it was standard on the formula "S" barracudas with 3:23 gears if you didnt order the optional 8 3/4 rear and should have been optional on most other models
Grinder
Banned
Could be ordered as an option for any car with a 7 1/4. But the one I had came out of a 66 Formula S Barracuda.
Adding the suregrip is not a cost effective way to beef up the 7 1/4. I would only do it if you find the sure grip for a decent price and never plan to see 300+ hp. Using a 8 1/4 or ford 8.8 is the way to go as far as cost goes.
Adding the suregrip is not a cost effective way to beef up the 7 1/4. I would only do it if you find the sure grip for a decent price and never plan to see 300+ hp. Using a 8 1/4 or ford 8.8 is the way to go as far as cost goes.
dgc333
Well-Known Member
The 7.25 was a perfectly acceptable rear end for it's intended applications, \6's and non performance small block v8's, it was even used on 2wd Dakota 4cyl and v6 pick-ups up to 96.
grimreaper
Cross Member
I've got a pile of 7-1/4 rears which I have ripped the pinion crossshafts right out of the carrier assy.and then trashed everything else. The design is just too small and weak to hold up to any power, including stock 273's. I do have a 7-1/4 Sure Grip in a 64 Barrucuda that has lasted since the car was new, and held up to a little mild punishment, but I'm guessing they are harder to find than a reasonably price 8-3/4 and for sure an 8-1/4. I recommend an upgrade to at least an 8-1/4 or just wait (probably won't be long) until the 7-1/4 fails having a plan in place for a replacement.
Cooter
Well-Known Member
I had a 7.25" sure grip from a 273 Non-Formula S car. Automatic. It had a sure-grip tag on it. It had 3.23 gears. I got rid of it when i sold my 73 Dart. They exist.
340mopar
Sorgermotorsports
When mine broke it was the spider gear shaft.
Chuck
Chuck
69B-Cuda
Well-Known Member
if you don't have the knowledge, skills, friends, or tools to swap out a rear end, you will not be able to install a suregrip carrier in your 7 1/4. It takes more tools and knowledge and tools to set up a new carrier in a rear end than to swap the whole thing out.
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