Pinion seal change on 742 case question?

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    Author Topic: Pinion seal change on 742 case question?  (Read 3815 times)

    Offline 71340RT

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    Pinion seal change on 742 case question?
    « on: August 03, 2007 - 01:45:01 PM »
    My 71 Challenger RT has the 742 3rd member and has started leaking gear oil at a pretty high rate. I have a seal part number 2404121 from chrysler bought some time ago. Is the right seal for my case or not? I have never had a pinion apart and need to get it fixed before the drive out to the Mopar Nats. Do I need any special tools and will the old seal just come out and the new seal drive in without any special things needing to be done? I have some pictures of the seal and I will attach them here. Thanks for any help in advance and I will work on this Saturday or Sunday.
    Jeff
    « Last Edit: August 03, 2007 - 01:46:32 PM by 71340RT »
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    70 Plymouth Cuda 340 4-speed
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    Offline Chryco Psycho

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    Re: Pinion seal change on 742 case question?
    « Reply #1 on: August 04, 2007 - 09:03:02 PM »
    not sure if the seal is correct but mark the pinion nut , remove it & change the seal , it will pry otu & tap back into place , then retorque the nut until the mArks line back up
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    Offline 71340RT

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    Re: Pinion seal change on 742 case question?
    « Reply #2 on: August 05, 2007 - 12:59:01 AM »
    Thanks Chryco, I found the seal number on the internet and it was for the 1 3/8 pinion so I got the right one and have marked the nut so I can put it back to the same spot when I took it apart. I'll try to put it back together on Sunday and see if my leak is fixed.
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    70 Plymouth Cuda 340 4-speed
    71 Dodge Challenger RT 340 automatic
    1973 Dodge Challenger 360 automatic EFI
    2002 Harley Davidson Dyna Wide Glide
    2003 Dodge Stratus RT coupe
    2009 Challenger RT Classic B5 Blue
    2014 Ram Express 5.7 Hemi 4X4

    Offline scf100

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    Re: Pinion seal change on 742 case question?
    « Reply #3 on: August 05, 2007 - 12:45:51 PM »
    dumb question but why do you have to mark the nut?
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    1970 Challenger R/T convertible 383…. 4-speed…3.91 suregrip

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    Offline tactransman

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    Re: Pinion seal change on 742 case question?
    « Reply #4 on: August 05, 2007 - 01:34:16 PM »
    So you retighten to the same torque (or close) that it was originally.
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    Terry-tactransman 
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    Offline 71340RT

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    Re: Pinion seal change on 742 case question?
    « Reply #5 on: August 06, 2007 - 12:40:21 AM »
    I got the pinion yoke out with little problems and the seal in and everything back together in time to fill the rear end with gear lube and take the Challenger for a 20 mile test run. Everything seems ok and no more leak. The seal was just like the original which had the seal center area made out of leather instead of rubber. I would of thought over the years they would of made this seal out of rubber like the other 2 carriers seals are. I called around and everyone said the same thing about the seal they carried for the 742 carrier being made out of leather.
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    70 Plymouth Cuda 340 4-speed
    71 Dodge Challenger RT 340 automatic
    1973 Dodge Challenger 360 automatic EFI
    2002 Harley Davidson Dyna Wide Glide
    2003 Dodge Stratus RT coupe
    2009 Challenger RT Classic B5 Blue
    2014 Ram Express 5.7 Hemi 4X4

    Offline scf100

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    Re: Pinion seal change on 742 case question?
    « Reply #6 on: August 06, 2007 - 06:09:15 AM »
    Quote from: tactransman on August 05, 2007 - 01:34:16 PM
    So you retighten to the same torque (or close) that it was originally.

    ok, but why?

    does that let you know its torqued right or to prevent a vibration or?

    just wondering...
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    1970 Challenger R/T convertible 383…. 4-speed…3.91 suregrip

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    Offline tactransman

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    Re: Pinion seal change on 742 case question?
    « Reply #7 on: August 06, 2007 - 08:40:46 AM »
    The pinion bearings need to have a certain pre-load or "drag" you would normally check it with a deflecting beam style torque wrench when the rear end is all apart. Since you are not taking it all apart,you are using the mark on the nut as a reference point. (assuming it was torqued correctly to begin with)
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    Terry-tactransman 
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    Offline scf100

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    Re: Pinion seal change on 742 case question?
    « Reply #8 on: August 06, 2007 - 09:51:06 AM »
    Thanks, you learn something new every day!
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    1970 Challenger R/T convertible 383…. 4-speed…3.91 suregrip

    Triple Black

    Offline tactransman

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    Re: Pinion seal change on 742 case question?
    « Reply #9 on: August 06, 2007 - 10:08:48 AM »
     :2thumbs:
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    Terry-tactransman 
    Torqueflite/Automatic Transmission Specialist
    Union, Mo.
    Give a man a fish and he eats for a day,teach him to fish and he eats for a lifetime.
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