Hello,
I looked through the search feature and couldnt find an answer to this question: If i choose to build the stock 225, and I realize significant H.P. gains, either through cam and compression , EFI, or turbo,what will become of the factory 7 1/4 rear ? what reasonable power can be transmitted and still remain in service,
There is 4" on 5 all around. thanks

It really boils down to what kind of condition it's in and how you drive it...

The 7 1/4 lived behind lots of 318's in the 70's and could cope unless you drive like Bullitt or tended to dump the clutch a lot...

If you drive like a sane person and only 'push' the rear occasionally, it should last quite a while...but if you decide that a 14 sec 1/4 time, 300 hp, and you like to get to the next light as fast as possible most of the time, you're looking at getting a better rear (8.25,8.75,8"...?)

-D.Idiot

Mine lasted for years and years.....as soon as I upped the ante to about 180-200hp it was toast.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

The 7 1/4 will take a lot more then most give it credit for. You would be supprised what a 7 1/4 clutch type sure grip rear will handle. I have been running the same 3.91 SG 7 1/4 since 1974, in 4 different cars. I have no idea how many 13 sec passes it has on it.

PS: I will be building a 4.56 SG 7 1/4 in the near furture.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

What Charlie says is true. The old 4-pinion (spider gear) 7 1/4 Sure Grip was pretty good. Most folks that break 7 1/4s break the spider gears as the open differentials only have 2. I say if you have a good 7 1/4 keep it, but don't put any money into it when it breaks.

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Joshua

The clutch type SG units have 4 spiders. The cone type only have 2 spiders. As rare as theses SG units are, and any SG is better then none, try for the clutch type.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I bought a clutch type SG recently. It was missing the 4 spiders and cross X cross pins. The seller said they are they same as the ones used in a 8.75 clutch type SG and he robbed them to replace the broken ones in his '68 RR. I have an old 8.75 clutch SG to rob parts from so I bought it. It will be awhile before I can get to it so for now I'm not sure they swap. If they do, that explains why the 7.25 rear with clutch SG outlasts any of the peg leg 7.25s.

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Slant Cecil

Was there a stock ratio for a 7.25 diff, that would have started out in my 67 A body /6; 3 on tree? Anyone in the know?

My '67 Valiant with the 225 3-speed originally had 3.23s.

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Joshua

Thanks Joshie225, I just swapped in an A-833 OD 4-speed. It seems to go pretty well with the diff and slightly built up 225. Not a dragster, but I don't drive like that anyhow.

Sorry, but they're nowhere close. The 8.75 is much larger.
See attachments. All part numbers are different.




Bob

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Robert Troy
69 slant 6 OD4 Barracuda conv
68 383-S 4 speed convertible

i came across a posi 7 1/4 what would make this different vs the SG 7 1/4?

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1976 Plymouth Feather Duster
2002 Dodge Dakota 4.7l v8

Positraction was Chevrolet's marketing name for their limited slip differential. Sure-Grip was Chrysler's. Studebaker called it Twin Traction. Lots of names for the same or very similar limited slip or improved traction differentials.

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Joshua

ok, i found one for $450 with 2.78 gears,is that a good price?

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1976 Plymouth Feather Duster
2002 Dodge Dakota 4.7l v8

I don't believe that ratio has ever been made available in the 7 1/4 or any other Chrysler rear axle I'm aware of. 2.76 I would believe. Also, that's about double what I'd pay. I paid $150 for an 8 1/4 open rear end because it's stronger, had the ratio I wanted and I have a loose 8 1/4 Sure-Grip.

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Joshua