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Discussion Starter · #1 ·
ok so I have these to casting numbers
2723676
23258

Ok it's a 7.25 rear end and it's got 2.76 in it I'm just curious if it's the original rear end
It's 77 Plymouth Volare with a new high compression 360
 

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What was the original engine?
The 7.25" rear axle is weak and only found behind the slant 6 and some 318s.
 

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The 2.7 ratio was standard with the slant 6 and an automatic transmission.
you should be able to find a much stronger 8.25" axle or even an older B body 8.75" axle when the 7.25" axle breaks (which it almost certainly will behind the 360). Finding economy rated gears like 2.7 (or the common 2.2 used in later 8.25" axles) should not be hard.
 

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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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Is there anything currently wrong with it now? Noisy?
If you want to try and get maximum life from the 7.25" differential gears/bearings, change the hypoid oil to a 75W-140 synthetic hypoid lube:
68218657_420.jpg
Drive the 360 gently as the 7.25" isn't made for the torque of this engine.
 

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I had an 77 Aspen that had a 318, that I swapped a 360 into it....it had the 8 1/4" rear end in it,that held up to the motor pretty good. I had a .455 lift cam in it,so the motor had some grunt. So if the motor Isn't too radical...this should work for you. Otherwise look for a late 60's b-body 8 3/4" rear end :)
 

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Discussion Starter · #7 ·
I have done reading and I've seen that about 500hp is most you've wanted to put on a 7 1/4
I'm sure my engine doesn't make that, if it is I'd be surprised like crazy, and yes I'm currently looking for a bigger rear end, and the rear end is quiet and seems fine I believe we changed the fluid in it when we did the engine change witch wasn't that long ago
 

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Discussion Starter · #8 ·
And my dad (we're both MOPAR guys) has a 65 valant and it has a upgraded 318 with some nice heads and intake and he runs a 7 1/4 in it o think it had 3.23

Put that things had a lot of abuse and is still perfect
 

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I have done reading and I've seen that about 500hp is most you've wanted to put on a 7 1/4
I'm sure my engine doesn't make that, if it is I'd be surprised like crazy, and yes I'm currently looking for a bigger rear end, and the rear end is quiet and seems fine I believe we changed the fluid in it when we did the engine change witch wasn't that long ago
It's your money, but there is no way the 7.25" rear axle is good for 500 HP. A stock slant 6 with all of 90-95 HP will kill one.
 

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Been putting 300 HP from my modified 318 through a 7.25 for 15 years now. No problems. Got the 8.75 for when it breaks.
 

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Wow, it's 2 of these and 2 of those! I've repaired a few 7.25 rears, mainly spider gears. They are alright to a point! Take care of it and don't shift gears in snow or mud too fast and you should do alright for while. Look for a larger one though for security in the long run.
 

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had 77 aspen r/t, shoe horned 440 ,4 spd and 9.25 out of 77coronet police car. the 8.25 didn't break but swapped 9.25 to be sure.just had to relocate spring perches but fit in body fine.i agree you would have to be very careful with 7.25
 

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I haven't been careful....
 
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