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Thread: main reason 200case runs hot

  1. #1

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    the main reason the 200 case runs hot is because helical gears have finer tooth than a 205. a 200 case is stronger than a205, because the 205s gears are more coarse there is less fricton. early model military vehicles wernt desgined to run long distances on a hiway all the time. 5.89 gears 900-16 ntd fine tooth gears in tcase,4000rpm=heat!! before i went to a205 ,i welded fins on the 200. this helped alot but the noise from the case drove me crazy! again fine tooth gears. any way find a205 they are more user friendly. matt

  2. #2

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    Matt, there are a dozen theories on what makes them run hot. Mine is one of them that runs hot. Only at 60 though. I never go that fast anymore and it does just fine. Some designs out there in the automotive world had problems built in from the start. Like the 60 degree chev V-6's. Not a very good motor I hear. When I rebuild my transfer case I intend to mic absolutely everything. I just want to rule out some things. Thanks for the input. It will get put on the possibilities list..
    Liz, covid, murdered 10/19/21

  3. #3
    Join Date
    Dec 2003
    Location
    parsons Kansas
    Posts
    476

    Default

    I have several questions too that Im wondering about ! does it heat up with and with out front axle engaged? does it stop overheating with rear driveshaft swapped straight thru? I wonder if with rear driveshaft swap and lockout hubs would end the over heating cause you stop the front axle from turning and rear is straight thru, unless like some transfer cases the input isnt straight thru to rear output. it has to be something overlooked or miss designed?
    67 M725, 67 M715, 68 M715

  4. #4
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default

    I have lockout hubs on the front and mine still overheats. I have the straight thru rear swap and it still over heats.
    Even with the 75W90 synthetic, on a hot day, over 50 MPH for long and I'm overheating. On hills I have to let it slow down to whatever it wants...not pushing any more RPM's than 50 MPH equivalent on flat ground. If the outside temp is below 50, I can run close to 3 hours at 55-60 before it gets too hot. If the temp is below 20 degrees out, I'm hard pressed to get the case up above 140 degrees, first line of the gauge.
    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!!

  5. #5

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    I am aiming for stock, but cheat with lockouts. I over heated in the Tucson desert with an outside temp estimated to be around 65-75 degrees. We left early for that very reason. So yes Dave, they will still over heat with lockouts....
    Liz, covid, murdered 10/19/21

  6. #6
    Join Date
    Jan 2004
    Location
    New Haven, CT
    Posts
    1,954

    Default

    I guess the main point is that if the NP200 was mounted on a regular civilian 4x4, with 3.30 gears, the transfer case would only turn at roughly half the speed, so that overheating would never be a problem, unless you drove at 180MPH all day long.
    Those here with 4.56 gears, do you have any overheating problems??

  7. #7
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default

    I guess by factoring off my experiences we can make some conclusions...
    In the heat of the day in August...doing 50 MPH on flats and slowing to around 40 on hills, I can keep down to 240 degrees or less with lockouts, rear driveshaft swap, synthetic lube and 5.87 gears and 9.00X16 tires.
    If we only play with the gearing:

    Presently 5.87 @ 50 MPH= 2860 RPM
    With 4.56 gears this would be 64.5 MPH

    Presently with 5.87 @ 40 MPH= 2290 RPM
    With 4.56 gears this would be 51.5 MPH

    Definately seems that it would help quite a bit if 60 MPH was used as the top speed of the truck.
    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!!

  8. #8

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    I have the 4:88 Gears with the 38inch tires and mine would not heat up that much, but noise it does. I would roll with Luckypabst and his would be so hot you couldn't touch it where mine you could touch it for a sec and his was stock 5:88

  9. #9

    Default Fuel Pump rebuild Hints

    even w/driveline swap mine ran hot,ieven have 4.56s i could only go about 50-60 miles before i would start smelling it . it never puked 90w but it sure smelled like it. igot the idea of welding cooling fins from summit, they have a unit that slips over an oil fliter to cool the oil. and it does cool the oil iwas out of options so i welded 1/4x1 flat bar top and bottom as close to each other as i could ,not welding the full length but solid staggered tacks. the flat bar has to be fitted to the contour of the case. it does cool it off to where it didnt smell like burnt 90w. its alot of work but it helps.matt

  10. #10

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    Mine never gets hot. My first truck with everything stock could run down the highway with the speedometer pegged in excess of 60 mph for hours without the transfer case getting too hot to touch. I know this because I used to work for the previous owner and I drove it that way for days while we used to to drive back and forth to the jobsites.

    Rollie

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