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  1. #1
    I normally woulndt do this, but there are a few times where conditions were bad enough that i have. (White-out blizzard conditions)

    I've heard alot of people who disagree on this point, One group says that it should be fine to run it at any speed, the other believes that running it over 40 will do damage to the transfer case.

    Now, i know that the dana 300's are built pretty tough, but i'd like to get some opinions from other jeepers on just how jeep drivetrains would fare at highway speeds.
    \'82 CJ-7 - AMC 258 -
    Mods: Weber Carb, Borla Catback, Juicebox TFI, 31\" BFG AT, Powermaster 150a alternator, H4 headlights, blazer heater motor conversion, WORKING gas gauge.
    Now with 80% less rust!!!

  2. #2
    Join Date
    Dec 2002
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    Boca Raton, FL
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    1,798

    87 wrangler liftgate

    I dont see why this would be bad. My grandcherokee has full time 4wd. so I am in 4wd no matter what speed I am in. I also have driven in 4wd -Hi in my TJ and never noticed a problem. Being in CNY sometimes there is a foot of snow on the highway. Remember though if it is a white out and there is a ton of snow and ice you shouldnt be doing 40+ mph anyways.

  3. Hello again, Chinard,

    I thought it would be possible to give you an authoritative answer by quoting from a copy of the 1985 CJ/Scrambler owner's manual.

    I just went through the entire manual and, believe it or not, AMC did not include any maximum vehicle speed limitations for four-wheel drive -- high or low range -- in the manual.

    Go figure!

    Regards,

    Gadget

  4. #4
    The Jeep website where they talk about how their 4wd system works says - "4H - Must shift under 55 mph". Sounds to me like you'd have no problem.

  5. #5
    this is pretty much what i thought.

    I think alot of these "general fears" in regards to 4 wheel drive stem from SUV's that have crappy transfer cases and are driven by soccer moms who throw it into 4 wheel drive every time they get a little bit of rain.

    The main reason why i avoid keeping it in 4 wheel is purely gas consumption
    \'82 CJ-7 - AMC 258 -
    Mods: Weber Carb, Borla Catback, Juicebox TFI, 31\" BFG AT, Powermaster 150a alternator, H4 headlights, blazer heater motor conversion, WORKING gas gauge.
    Now with 80% less rust!!!

  6. #6
    how about dangerous -with respect to handling at higher speeds, the case isnt designed like an Audi's Quattro, or a Subaru....

  7. #7
    Quote Originally Posted by hoobness
    how about dangerous -with respect to handling at higher speeds, the case isnt designed like an Audi's Quattro, or a Subaru....
    It's a jeep!
    It doesnt GO to higher speeds

    Seriously tho, I have found that i get alot less steering wobble when i have 4wd enabled on the highway.
    \'82 CJ-7 - AMC 258 -
    Mods: Weber Carb, Borla Catback, Juicebox TFI, 31\" BFG AT, Powermaster 150a alternator, H4 headlights, blazer heater motor conversion, WORKING gas gauge.
    Now with 80% less rust!!!

  8. #8
    You'll be fine at any speed in 4hi, it's what it was designed for. The 55mph mention above is for newer chain-driven transfer cases I believe, and it's meant for shift-on-the-fly 4wd, don't engage 4hi at speeds over 55mph. Once in 4hi, you can exceed 55, but if you need 4wd, who wants to?

    4hi is also okay for spotty slick spots, like a snow drifted road that has spots that have blown clear of snow. You don't have to shift to 2hi for those, the 4wd system will be fine for small clear spots.

  9. #9
    if you need to be in 4wd, you won't be doing much over 30-35 anyway so who cares?? but you wont do damage to the t-case.. if you have full time 4wd you are fine, with part time you will cause your rear tires to drag, causing tthem to wear out much faster on dry pavement.
    When I Die, Bury me in my JEEP. 'Cause it's never been in a hole it couldn't get out of!

    1995 Grand Cherokee w/ swaybar disconnects and 30" tires and a 2000 Grand Cherokee stock.

  10. #10
    The rear tires dragging is true! I freaked out when I first noticed it. Do you know why they design it like that?-al

  11. #11
    how will your rear tires drag? they have the same gearing and should travel at the same speed
    93 YJ 4.0
    Spring Over, 33x12.50 Mastercraft Courser M/T, High Flow Exhaust, Diamondplate Rear Bumper, Trimmed Flares, 6\" spotters


    We, the Sovereign People of the Universe, wish to live in peace. We live among you, but we are not of you.

  12. #12
    They won't drag, but you may feel a little wheel skid or front end binding occasionally, it's when you turn or differences in tire height (uneven air pressure or wear) cause the transfer case to bind.

    Full-time 4wd jeeps have a viscous coupling in the transfer case that allows slippage, no binding between the front and rear axles. Part-time 4wd does not have this, hence occasional bindage.

  13. #13
    Quote Originally Posted by Snitty
    how will your rear tires drag? they have the same gearing and should travel at the same speed
    negative on that one... the transfer case does NOT have the same gearing from front to rear.. if you look inside, the gear on the front output shaft is a little smaller than the gear on the main output shaft... this causes slightly more power to be transferred to the front wheels than the rear wheels. the reason for this is simple.. 90% of 4 wheeling is done in forward, the uneven power split causes the frone wheels to pulll you up over the obstacle using the wheels that have the most weight over them. because of this, if you run in part time 4 wheel drive, the front wheels set the speed of the vehicle, causing the rear wheels to slip on the pavement and actually skid very slowly, wearing the tires down.. if you had a 50/50 split, you would get yourself stuck much easier than you do and would not be able to climb as steep a hill. All 4wheel drives are set up this way.. this is why the jeeps have the viscous coupling in full-time mode... the coupling allows the front shaft to slip slightly and the tires to spin at the same speed.
    When I Die, Bury me in my JEEP. 'Cause it's never been in a hole it couldn't get out of!

    1995 Grand Cherokee w/ swaybar disconnects and 30" tires and a 2000 Grand Cherokee stock.

  14. #14
    graewulf, I disagree with you on this, I don't believe that torque is sent to the front and rear at a different gear ratio in the transfer case. The transfer case, at least the 231, will change driveline speed by 2.72:1 to both the front and rear axles, the same. It's not 2.72:1 to the rear and 2.80:1 to the front or any other mix. If it were, you'd ruin the transfer case in short time.

    A viscous coupling is used in full-time systems simply because long-term 4wd on dry hard surfaces will introduce binding in the transfer case, from turns and slightly different tire heights from air pressure and wear.

    Your a little off on the weight transfer argument too, IMO. If you were to run a Jeep up a hill in rear wheel drive, it would make it further than if it were running 2wd with only the front axle pulling. As the weight shifts rearward going up a hill, most of your traction is in the rear. This is why many 2wd vehicles with a locker can go the same distance or further than many 4wd open diff vehicles.

    Take for example a jeeper who was running ARB's front and rear. The rear driveshaft broke on the trail and he had to limp the rest of the trail in front wheel drive. He tried to climb a slickrock boulder with both front wheels pulling and no luck, just lots of spinning. He then turned the Jeep around and backed up the rock, crawling without a single tire spinning. We use this same argument when Jeepers are trying to decide on where to install the first locker, front or rear. The rear is the obvious choice due to weight transfer.

  15. #15
    Well, regardless of the gearing specs, if you pay close attention, you can hear and feel the rear tires drag. You can really notice it when you have your top off. It is not severe, but it is noticeable.-Al

  16. #16

    how do I find the vent on the Dana 300?

    Quote Originally Posted by Bounty__Hunter
    graewulf, I disagree with you on this, I don't believe that torque is sent to the front and rear at a different gear ratio in the transfer case. The transfer case, at least the 231, will change driveline speed by 2.72:1 to both the front and rear axles, the same. It's not 2.72:1 to the rear and 2.80:1 to the front or any other mix. If it were, you'd ruin the transfer case in short time.
    There is a difference in the gearing form front to rear..... the 2.71:1 is the average of the 2.... you are only talking like 1 or 2 teeth difference from one gear to the other.... Unless the T-cases in jeeps are different than in 4wd trucks.. i know my mazda had an uneven power split. and you will drag rear tires if running 4wd on the highway, how do you explain this if it is a 50/50 split? they would run down the highway at the same speed, not dragging....
    When I Die, Bury me in my JEEP. 'Cause it's never been in a hole it couldn't get out of!

    1995 Grand Cherokee w/ swaybar disconnects and 30" tires and a 2000 Grand Cherokee stock.

  17. #17
    A pickup truck, such as your Mazda, is lightest in the rear, so any binding will cause the rear tires to 'drag', since it's the least resistance to the unloading of the bind that the drivetrain is in. I doubt it's because of this different gearing to the front and rear, but more likely caused by the front axle traveling a further distance in turns than the rear axle.

    If there's no viscous coupling, there is going to be binding between the front and rear on dry pavement, no matter what. Just hope you can get it to let loose as tire slip and not by grenading a transfer case.

  18. #18
    Just so people don't think I am nuts.... read this:
    http://www.jeeptech.com/xfer/np242.html


    Quote:
    The chain driven NP242 is a full time transfer case with a 48/52 torque split front and rear. It is possible to lock it into four low so it behaves like a part-time transfer case. When it is locked in, power will be split regardless of traction. The output for the front axle is on the drivers side. Low range is 2.72 and high is 1.00.

    Usage
    The NP242 is used in Grand Cherokees (ZJ) and Cherokees (XJ).
    End Quote

    So, there are transfer cases with an uneven torque split, hence rear tire drag. Some are 50/50 some are not...
    When I Die, Bury me in my JEEP. 'Cause it's never been in a hole it couldn't get out of!

    1995 Grand Cherokee w/ swaybar disconnects and 30" tires and a 2000 Grand Cherokee stock.

  19. #19
    hmm what transfer case r we talking about? a 300 242 or 231? i know that the 231's have an even split and there is no binding in the t-case unless your tire size is different of that the front and rear gears are dfferent. we had a whole arguement in tech school about this and finally went to an old teacher that was a jeep tech and got it settled on teh TJ there is a 50/50 split and thats the 231 t-case
    hellooo everyoneeee..
    '97 TJ, Black, 8" skyjacker lift w/33x12.50's, Vortec 350, 4L60e, mini spooled dana 44 front, Detroit locked dana 44 rear, moser axles and more to come........ Woooo Hoooooooo

  20. #20
    Quote Originally Posted by jeepin916
    hmm what transfer case r we talking about? a 300 242 or 231?
    I originally asked about this in respect to a dana 300, but it would be useful to include the others into this discussion.
    \'82 CJ-7 - AMC 258 -
    Mods: Weber Carb, Borla Catback, Juicebox TFI, 31\" BFG AT, Powermaster 150a alternator, H4 headlights, blazer heater motor conversion, WORKING gas gauge.
    Now with 80% less rust!!!

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