1. Airstream

    Airstream Member

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    Hi Guys.
    my car has a 8 1/4 diff in it 1978 Newport and i have a 1974 New Yorker parts car witch has a 9 1/4 diff in it.
    been thinking of lower the gears in the diff to 3.23 or 2.92
    as i am thinking to do some mod later to the 360 in the car was looking at 9 1/4 gears.

    But is there a differnce in 9 1/4s diff like early and later ?
    some of the cover don't look the same if this right, is the pinon and ring gear not the same to.

    any light wood help. as living on the other side of the world wouldn't like to buy something thats not right
    thanks.
     
    Last edited: Aug 6, 2011
  2. commando1

    commando1 Mr. Normal FCBO Gold Member

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    A 9 1/4 is a 9 1/4 is a 9 1/4...
    The only difference is the axle lengths between the B's, C's, etc...

    Mosl Jeep 9 1/4's came with 3.23
    If looking for one at a salvage yard, say "Jeep' or Dodge truck instead of Chrysler. Say Chrysler and they'll tell you they don't have any. Use Jeep, truck and demo derby forums looking for one.
    360? Don't go higher than 3.23. 2.91's won't cut it with a 360 if you mod it. When you mod it you'll lose your low end grunt.

    That all said, I find it extremely hard to believe your '78 came with an 8 1/4. In fact, I know it didn't...

    http://www.hemmings.com/mus/stories/2005/12/01/hmn_feature25.html
     
    Last edited: Aug 7, 2011
  3. Airstream

    Airstream Member

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    Thats for that read. i looking at just buying the pinon and ring gear and maybe a suregrip as well.
    Thank you.
    P.S.

    Commando 1 my diff in the newport is 100% 8 1/4. The car has never been play with. i am only the 3rd owner
    The motor is in good shape and i will only hot up a bit once the motor starts play up.
    so the 9 1/4 diff is just something to play with.
    Thanks again.
     
  4. commando1

    commando1 Mr. Normal FCBO Gold Member

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    I have to believe you since I have never personally looked at a 78 with the 360. I just learned something new.
     
  5. Big Blue

    Big Blue Member

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    if you use rock auto catalog and look for for differentials for the newport or new yorker it gives 8.25 as an option.
     
  6. polara71

    polara71 Old Man with a Hat FCBO Gold Member

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    Stan has been humbled....
     
  7. commando1

    commando1 Mr. Normal FCBO Gold Member

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    Hell, I find out something new every day.
    For example, Found out last night I ain't %$& 21 anymore....:mornincoffee:
     
    Last edited: Aug 9, 2011
  8. 1978 NYB

    1978 NYB Warfighter FCBO Gold Member

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    I just climbed under my '78 NYB and I have a 400 with the leveling suspension and a 8 1/4 axle. 10 bolt cover on it.
     
  9. Big Blue

    Big Blue Member

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    No sh!t? I figured just the 360 would have the small rear. Btw, what is the leveling suspension?
     
  10. polara71

    polara71 Old Man with a Hat FCBO Gold Member

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    I agree...... 8 1/4 on a 400? I wouldn't have thought so
     
  11. commando1

    commando1 Mr. Normal FCBO Gold Member

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    Geedammit! Where's my stupid %^&$ reference book?......
     
  12. 1978 NYB

    1978 NYB Warfighter FCBO Gold Member

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    Me too! When I first bought the car, I changed all the fluids, I bought a rear diff gasket and for the hell of it, I pulled it out of the Fel-Pro box just to make sure it matched up and whoa!!! There's 2 extra bolt holes in the gasket. I checked the application on the box, right gasket for a 9 1/4, just happened to have a 8 1/4 axle. Lucky me, I work on the car at the auto craft shop on Aberdeen Proving Ground. That would of been embarrasing if I would of popped the diff cover off first.

    I don't know for sure, Commando probably knows, I think the suspension leveling option was only available on '78 NYB's. It has a lever mounted on the left side of the axle that connects to a valve mounted to the frame, as the payload or stance of the car changes, the height of the body relays through the valve to raise or lower the suspension by way of a vacuum pump mounted in the left front wheel well. The pump operates off the vacuum of the engine. It has special "air type rear shocks" that have hoses that go to the top of the valve that mounted on the rear of the frame. I don't know if mine works or not. The lever that mounts from the axle to the valve is broke. I can easily weld that back together. I can test the vacuum pump to see if it works and then check the shocks to see if they don't leak. I'm sure that parts are probably nonexistant. If it doesn't work, I'll just replace the shocks (and keep the old ones).
     
  13. commando1

    commando1 Mr. Normal FCBO Gold Member

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    I HIGHLY (and I can not emphasize it enough) that you join us over at:

    http://autos.groups.yahoo.com/group/NewYorkerOnline/

    There are guys in there that know the air leveling suspension (along with every other 74-78 C-body minutia) intimately. I personally have never seen one.
     
  14. Big Blue

    Big Blue Member

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  15. commando1

    commando1 Mr. Normal FCBO Gold Member

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    Just talked to a guy who owned two Formal NYB's with big blocks and 8 1/4's...
    Still learning. Every day, still learning......
     
  16. 1978 NYB

    1978 NYB Warfighter FCBO Gold Member

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    I've found the leveling suspension by accident when I discovered the 8.25 axle gasket fiasco. Everytime I work on the car I find something new or very strange. I also believe that the 400 engine is the only Chrysler (or Mopar) engine without an emission air pump. It has the bracket for it but no air pump. No idea why. The 225, 318, 360, 440's all have an emission air pump.
     
  17. 1978 NYB

    1978 NYB Warfighter FCBO Gold Member

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    Thanks Commando1. I will join when I get home. Can't do it from work.