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Thread: Transfer Case Leaks

  1. #1

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    My transfer case is leaking quite a bit. It appears that the fore and aft seals are the culprits. The thing that really strikes me as odd is that my T98 doesn't leak whatsoever, not a drop. On the opposite end of the spectrum, my transfer case leaks like a tipped over can of oil.

    Does the transfer case require any special tools to work on it?

  2. #2

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    Fred,

    It requires a socket to fit the nut. The front output and the rear are the same size nut (if memory serves) and the seal is the same. It takes about 2 hours to do the seals. The only hard one is the input.

    The reason that your 200 is leaking, but your 98 isn't has alot to do with the cooling of the 98 versus the cooling of the 200. 200's tend to run hot and melt seals. You might want to flush the 200 a bit while you got it apart to get any rust out, and that is rumored to make it cool better.

    If you have an impact wrench, then the seal replacement is a breeze. If not then a cheater bar helps as the nuts have to be torqued to 200 (I think).

    Seal part nubmers:
    National #450308 all 3 are the same.

    Hope this helps....and is right.
    -B.

  3. #3
    Join Date
    Dec 2003
    Location
    Giddings, Texas
    Posts
    7,729

    Default

    The e-brake also helps to hold things still while you loosen and tighten the nuts. Otherwise, be sure to block your wheels so you don't wrench the truck over your legs.
    Remember if you didn't build it you can't call it yours.

    6.2 powered M715, 5 M1009's, M416, 2 M101's, 2 M105's, 3 M35's, M1007 6.5 turbo Suburban project called Cowdog.

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  4. #4

    Default NV3550

    Quote Originally Posted by Brian.....Sisson
    Fred,

    It requires a socket to fit the nut. The front output and the rear are the same size nut (if memory serves) and the seal is the same. It takes about 2 hours to do the seals. The only hard one is the input.

    The reason that your 200 is leaking, but your 98 isn't has alot to do with the cooling of the 98 versus the cooling of the 200. 200's tend to run hot and melt seals. You might want to flush the 200 a bit while you got it apart to get any rust out, and that is rumored to make it cool better.

    If you have an impact wrench, then the seal replacement is a breeze. If not then a cheater bar helps as the nuts have to be torqued to 200 (I think).

    Seal part nubmers:
    National #450308 all 3 are the same.

    Hope this helps....and is right.
    -B.
    Hey Brian, thanks a lot for the information. Gee, I wonder if anyone has ever tried to adapt a transmission cooler into the NP200 to help it run cooler. Do you think that that would be feasible?

  5. #5

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    Quote Originally Posted by Barrman
    The e-brake also helps to hold things still while you loosen and tighten the nuts. Otherwise, be sure to block your wheels so you don't wrench the truck over your legs.
    Thanks, Barrman. Yes, wrenching an M715 over your legs would be a very bad thing.

  6. #6
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

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    The proper torque is 140-160 lbs foot.
    The cooler idea has been thought about for a long time but no one has come up with a cheap way to pump heavy weight gear oil around the system to do it.
    Plus heat is a symptom of a problem...one my t-case suffers from while some of them dont...there is an underlying problem, probably bearing clearances hat need adjustment, maybe combined with slop in the internal gears that, if corrected, would be a much better soluton than to run a cooler...treat the condition(s) that is really causing the heat...my opinion...
    brute4c
    Lord send your Holy Ghost into our hearts and make the desire of our hearts Your Will.

    Pro-choice, that's a LIE, babies don't choose to die!!

  7. #7

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    Fred, I had to buy a 1 5/16ths socket (Craftsman) to take the yokes off, but the problem was that it didn't fit inside the yokes and I couldn't get a grip on the nut. I took it to a friend and he machined .05 inch off the outside of the socket and it worked like a charm. When you put them back, the torque is 140 -160 pounds.
    I measure work by how many beers it takes, so my adivce- stop in at the Kum & Go for an 18pk just to be safe.
    -G-
    Mine just keeps getting taken further apart.

    Maybe it\'s all the beer.

  8. #8

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    YUP, inch 5/16's is the socket and you'll need to put it to the grinder just a tad to get it to fit into the yokes. If you don't have impact access, drop the front driveshaft, take a 1" piece of pipe and bolt that into the yoke so that it bottoms out against the frame when you're losening the rear on. On the rear, you may need to chain the pipe to the bottom of the frame. Doing this will prevent the truck from moving and about the time you've got real good pressure on the breaker bar...running out of room. Pipe in yoke works great!!
    Big Blocks RULE!

  9. #9
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default School

    I'm gonna guess you guys are using 1/2 inch drive sockets....I used a 3/4 inch drive socket when I did mine, no grinding was needed on the socket...just fyi...
    brute4c
    Lord send your Holy Ghost into our hearts and make the desire of our hearts Your Will.

    Pro-choice, that's a LIE, babies don't choose to die!!

  10. #10
    Join Date
    Dec 2003
    Location
    Lone Pine, CA
    Posts
    451

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    I used a 3/4 drive Craftsman socket - required grinding the OD.

    I happened across a photo in a completely unrelated topic showing a Tilton brand electric pump used to circulate gear oil through a cooler to keep a diff cool. Probably not a cheap option, but apparently there is something designed for what we need.

    On the note of cooling, I got a response from Chuck's Trucks (they use the 200 in their corny rockwelled trucks). According to them they never have heat problems unless the oil is too low. Of course they probably don't spin the same rpms as us for extended trips and I bet those trucks don't see much freeway use.

    Chris

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