7 1/4 Posi??????

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xLURKxDOGx

xLURKxDOGx

"An angel fat, at satan's feast"
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I read somewhere on this site that a posi 7 1/4 existed. I was at the junkyard this past weekend and noticed a barracuda siting on top of another and out of curiosity i spun it and both sides turned, does this tell me that its a posi rear end or am i hoping thats what it is?

Also, what years/models did they come in? Im putting a 273 commando in my 63 valiant and figured this would be an upgrade? from what i have in there now, it should bold right up from what i gather but not 100% on the driveshaft.

Thanks,

Jake
 
If you can get someone to try and hold the other side while you turn it and cannot because they are holding it still, it is a sure grip.

If it still turns and turns the yoke while the other side is held still it is an open differential.
 
1967 barracuda formula S cars with a 273 4bbl/automatic supposedly came with a sure grip 7.25 with 3.91 gears. I for sure had a 7.25 sure grip unit with those very gears not too long ago too.
 
You could get a sure grip unit in any 7 1/4, just check the option box and it coulve been yours!
 
xLURKxDOGx said:
I read somewhere on this site that a posi 7 1/4 existed. I was at the junkyard this past weekend and noticed a barracuda siting on top of another and out of curiosity i spun it and both sides turned, does this tell me that its a posi rear end or am i hoping thats what it is?
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Did they turn in the same direction? If so, yes. If opposite directions, no.
 
I had a 67 Dart slant 6 car with a 3.23 sure grip 7 1/4. Back then you could order just about anything.
 
nm9stheham said:
Did they turn in the same direction? If so, yes. If opposite directions, no.
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That's not true every time. With no drive shaft, sometimes an open diff will pass your test. If you do it like I described in post #2 it is foolproof.
 
Jake.....Repeat after me....Sure Grip, Sure Grip.

Posi is for the guys that dont know who their dads are.
 
had a 66 Canadian valiant with a 3.23 sg...I have sales brochure saying sg not available with 3.91 for the 7.25
 
doug 371 said:
had a 66 Canadian valiant with a 3.23 sg...I have sales brochure saying sg not available with 3.91 for the 7.25
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There is no 3:91 gear available for the 7 1/4 with a sure grip! Without my books here I can't verify, but I don't believe that there is a 3:91 year available in any 7 1/4
 
doug 371 said:
had a 66 Canadian valiant with a 3.23 sg...I have sales brochure saying sg not available with 3.91 for the 7.25
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I had one :) Might not have been original but it was for sure a 3.91 ring and pinion on a cone type (I think) sure grip unit


http://www.dippy.org/forum2/index.php?topic=73.0 this is the page I got my info from. About halfway through the second paragraph. Down the page a little it lists all the factory ratios as well (according to this website)
 
If it is real cheap like $100 or less it would be worth it. If more don't waste your money. I blew mine up withe my /
 
xLURKxDOGx said:
I read somewhere on this site that a posi 7 1/4 existed. I was at the junkyard this past weekend and noticed a barracuda siting on top of another and out of curiosity i spun it and both sides turned, does this tell me that its a posi rear end or am i hoping thats what it is?

Also, what years/models did they come in? Im putting a 273 commando in my 63 valiant and figured this would be an upgrade? from what i have in there now, it should bold right up from what i gather but not 100% on the driveshaft.

Thanks,

Jake
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Out of my curiosity, what yard were you in that had 2 Barracudas? DVAP?
 
RustyRatRod said:
If you can get someone to try and hold the other side while you turn it and cannot because they are holding it still, it is a sure grip.
Thats something i need to do, thanks for the heads up rusty!


nm9stheham said:
Did they turn in the same direction? If so, yes. If opposite directions, no.
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I dont recall but im going back to try rustys suggestion.

Johnny Dart said:
Jake.....Repeat after me....Sure Grip, Sure Grip.

:farao:


Moparbrad said:
Out of my curiosity, what yard were you in that had 2 Barracudas? DVAP?
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Yeah, theres a few of them there.
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Click to expand...
 
xLURKxDOGx said:
I read somewhere on this site that a posi 7 1/4 existed. I was at the junkyard this past weekend and noticed a barracuda siting on top of another and out of curiosity i spun it and both sides turned, does this tell me that its a posi rear end or am i hoping thats what it is?

Also, what years/models did they come in? Im putting a 273 commando in my 63 valiant and figured this would be an upgrade? from what i have in there now, it should bold right up from what i gather but not 100% on the driveshaft.

Thanks,

Jake
Click to expand...
No you’re not dreaming I have a 73 340 duster with a 727 trans and a 7 1/4 rear end sure grip Posi. 3.91
 
7 1/4 rear was available as open or SG. early SG's were clutch, later ones were cone. I'm not sure of the year break. Clutch types are more desirable, as they have 4 spider gears, and the cone types only had two. 3.91 ratio was available from the factory in some year new vehicles. From the Direct Connection Program you could get 4.11, 4.56, 4.88, 513 gears. I have been told a 5.38 was also available, but have never see one, or seen documentation for one. I just sold a 3.91 SG unit. I totally rebuilt it after removing the 5.13 gears. The big problem with 7 1/4 rears is parts are made of unobtanium. It took me several years to find all the parts.
PS: These rears are stronger than most people think. I ran a 7 1/4 3.91 SG in my 66 Cuda street/strip car for about 5 years. 3250 lbs, 170 slant six with nitrous, 904 with a 8 inch converter and slicks. Car ran low 13's and would 60 ft at 1.81
 
Someone on Facebook Marketplace sold me an SG 7-1/4. I paid to have it shipped. He turned one wheel and the other turned in the same direction. I paid to have it shipped. when I received it, it was not an SG. the gears were rusted stuck. I was out $600 after shipping. I didn't blame him. So, testing it as described in post #2 is a MUST. I did eventually buy one here on FABO. replaced the seals and bearings, checked clearances and it has been working fine. [I don't do hole-shots with my 273]
 
"Used extensively in passenger cars beginning in 1972, the 8 1/4-inch housing also was used in 1971 and newer Dodge B-vans and pickups. This differential is a great candidate for upgrading many Mopar 7 1/4-inch rear ends by adding strength without spending a lot of money. Original passenger car ratios ranged from 2.45:1 to 3.21:1. The truck 8 1/4-inch differentials had additional ratios of 3.55:1 and 3.90:1. A fuel-sipping 2.24:1 ratio was offered in some 1980-'81 passenger car applications"
 
Scody21 said:
Something is fishy with this. A 340 with a 7 1/4 would have not been factory…
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Mtrhead said:
8.25
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Scody21 said:
At the least with a V8 car..
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A 340 car should have had an 8.25 rear in ‘73.

The 8.25’s didn’t come in all v8 cars 73+, you could get a 318 auto with a 7.25. But with a 340 the 8.25 should have been standard. So either it was swapped out or the 8.25 has been misidentified. Or maybe the 340 has.
 
My 69 Dart had a 7.25 sure grip in it. It went to a member in the Phoenix area that wanted it for a resto on an early A.
 
toolmanmike said:
"Used extensively in passenger cars beginning in 1972, the 8 1/4-inch housing also was used in 1971 and newer Dodge B-vans and pickups. This differential is a great candidate for upgrading many Mopar 7 1/4-inch rear ends by adding strength without spending a lot of money. Original passenger car ratios ranged from 2.45:1 to 3.21:1. The truck 8 1/4-inch differentials had additional ratios of 3.55:1 and 3.90:1. A fuel-sipping 2.24:1 ratio was offered in some 1980-'81 passenger car applications"
Click to expand...

72bluNblu said:
A 340 car should have had an 8.25 rear in ‘73.

The 8.25’s didn’t come in all v8 cars 73+, you could get a 318 auto with a 7.25. But with a 340 the 8.25 should have been standard. So either it was swapped out or the 8.25 has been misidentified. Or maybe the 340 has.
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I’m not posting this as a specific part of the conversation, but just as information you two may or may not find useful, even if just to help someone else.

Not real long ago I ended up with a 73/74 8.25 open rear end.
After some investigation I found that with different carrier bearings, the Durango 4x4 carrier with the cone style sure grip fit perfectly.
The 3.55 gears out of the Durango also went in without issue.
The pinion bearings were even the same as the 73/74 rear end used.
The Jeep Grand Cherokee disc brakes went on with a very slight mod and longer wheel studs, so I ended up with a 3.55 geared 8.25 sure grip with disc brakes.

If I ever trash or wear out the sure grip section, I can get another one for about 30 bucks.
 
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