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Thread: np-200 and heat?

  1. #1
    Join Date
    Dec 2006
    Location
    Farmington hills MI
    Posts
    251

    Default np-200 and heat?

    I have seen this posted so many times, and maybe I just don't get it. So correct me if Im wrong, but isn't the heat in the t-case caused from running the truck so fast with the stock axle ratios, and wouldnt a np205 have the same thing happen? Or, if the rear output shaft was switched to a straight through type set up, would this problem would go away, and there for, the problem doesn't happen to the np-205 because of the rear output? I have not yet driven my truck this fast, or I would have figured this all out. Much of this is just thinking out loud, but Im guessing its both the high rpms and the off set rear of the np-200 that is causing the high heat or cooking of the lube. So, off the top of my head, wouldnt the 205 and the 200 then be almost identical if I was to change the out put to a straight through?
    I guess I could look up both, in my books, if I could get to them, but they are in my garage and Im in the house. Oh, and my back wont allow me to make that trip. When I step wrong, I get PAIN

  2. #2

    Default

    This has been discussed since the beginning of time...LOL

    The gears in the 200 and 205 are cut differently, seems to be the general concencious of why the 200 builds more heat than the 205. Many theories on coolers/fluids and changes have been debated, but it seems the cheapest and most logical conclusion is that if you want to drive over 45 for extended periods of time, you need to swap to a 205. Center output may help a smidge, but it's not the cure.
    This post is closed-captioned for the hearing impaired.

  3. #3
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default

    Yep to all that....

    The NP202 and NP205 are 60's updates to the 40's design that brought forth the NP200...the changes that were made in that update allow the NP202/205 to live comfortably in an environment the NP200 cannot....and wasnt desgned for anyway...remember, it was designed for vehicles, flatheads, with governors at 2800-2900 RPM's max. THE M715 does 3400+ RPM's at 60 MPH stock...
    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!!

  4. #4
    Join Date
    Dec 2006
    Location
    Southern Indiana
    Posts
    246

    Default

    OK, so running 456's, overdrive and turning around 1800 at 55 will the 200 live? I'd like to just leave mine where it is(If I don't just use the j-truck drivetrain that is).

  5. #5
    Join Date
    Dec 2006
    Location
    Northwest Montana
    Posts
    33

    Default

    Mine never seemed to overheat. I took mine on a 40 mile round trip at 55 with no problems.

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

    Default

    I have run mine with a temp gauge, synthetic lube, driveshaft swapped to center output....

    On a warm to hot day:
    about 1 hour at 60 and the temp goes through the roof
    about 1¼ hours at 55 and the temp goes through the roof
    I found that at 50 MPH max and letting the truck slow down on hills...keeping the RPMs roughly constant...the temp stays just barely in the safe zone.

    In my truck, once 240 is exceeded on the gauge plumbed directly into the drain hole of the NP200, the temp goes up at an alarming rate....like from 240 to 280 in a quarter mile or less...and still climbing...

    Keeping my speed to 50 and letting it slow on hills left me looking at just under 240 most of the time durng daylight hours. Once the sun went down AND we climbed a big hill that brought a definite drop in ambient temperatures, the gauge dropped some. We could run 55-60 for several miles, then have to slow back to the 50 method until it cooled again.

    These are my experiences, your mileage may vary...
    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
    Join Date
    Dec 2006
    Location
    Farmington hills MI
    Posts
    251

    Default

    Jon, I remember back some time ago on the old site you did that to your t-case. If its not too much trouble can you tell how much of that test truck as I will call it, was stock? Axle ratio, tire size, tornado 6. Thanks.

  8. #8
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default

    The driveshaft was swapped to the center position, lockout hubs on the front axle, civvy 2 barrel carb and civvy ignition on an otherwise stock 230. Eaton full synthetic lube in all gear boxes.

    Gears, tire sizes, trans and tcase otherwise stock.

    Speed was checked by Wi715 in chase truck on that trip with GPS...he was a little surprised I could keep the speed so steady on such a long trip...50 was actually 49.7 MPH almost all the time...close enough...
    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!!

  9. #9
    Join Date
    Dec 2006
    Location
    Farmington hills MI
    Posts
    251

    Default

    Thanks Jon!

  10. #10
    Join Date
    Dec 2006
    Location
    KINGSPORT, TN.
    Posts
    229

    Default

    the np200 is straight cut gears and the np202,205,s are helical gears like the diffs.do yourself a favor and swap em out.

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