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np241 vibration

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by foxman, Dec 10, 2002.

  1. foxman

    foxman 1/2 ton status

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    Has any one had a np241 go bad, I think mine is. I hear a horrid noise coming form it when running it with the rear wheels off the ground. The clutches don't seem to catch untill it reaches a high RPM like 2200. I also get a bad vibration on the highway which seems to be related to this. any ideas?


    Thanks,
    Jeremy

    OK here's some more info...
    This 90 k5 blazer stock with 32"s has a vibration on the highway which seems to be the worst at @ 45-55 MPH while the trans is in overdrive. I got it home the other night and checked the ujoints for play and ran it in drive with the rear wheels off the ground. while in the truck from an Idle everything seems smooth and quiet. then when applying the gas a kind of churning noise seems to build with the rpm's and if I rev it off an idle, the speedometer reads under 15 mph untill I reach about 2200 rpms and then the churning noise comes on strong and the speedometer jumps up to about 55. It seems like something isn't grabbing all the way in the T-case. I refilled the fluid with the recommended atf a while ago so that should be ok. The vibration really seams to go along with the noise. Please help, what are my options?


    thanks
     
  2. tori89k5

    tori89k5 1/2 ton status

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    ....ummmm........ ya..... we're gonna need a little bit more information here.... yah, riiighhht....

    ....anyone else see "Office Space" ? /forums/images/graemlins/grin.gif
     
  3. foxman

    foxman 1/2 ton status

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  4. tori89k5

    tori89k5 1/2 ton status

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    Dooode,.... we cant help you cause we dont know your truck. Give us more info. Such as year, amount of lift, tire size... and what you have done so far to cure the problem.
     
  5. imiceman44

    imiceman44 1 ton status

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    You seem to be thinking the transfer case has clutches and it's slipping, or you confuse your transmission with your T case. which is it?
    did you hear the same noises and feel the same vibrations while driving it?
    If you are doing this with th truck lifted off the ground you will have weird things happen.
    Please clarify those points I mentionned above so we can proceed.
    /forums/images/graemlins/thumb.gif
     
  6. foxman

    foxman 1/2 ton status

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    It is a 90 K5 stock springs, 32" tires, stock 700r4/NP241 T-case. The rear U-joints have been repleced, T-case fluid changed. That's about it. The T-case was bone dry for about 6 months I think because the front output shaft seal went slowly and then got ripped up and cracked that when I tried to add fluid it came pouring back out. so I replaced that seal and filled it back up. It makes the noise to a lesser effect on the road. the vibration happens mostly in overdrive at low speeds I think it's because there's less torque on the loose/worn part, letting it slop around. I'd like to know what in the world it could be. I can hear this crazy noise coming from the t-case and feel it with my hands when lying under the truck with the shaft spinning and someone giving it gas to go around 45 mph. It will also vibrate like it does on the road, only not as bad when jacked up. then there's the whole slipping thing. off an idle the speedometer hardly reacts to the throttle if you go slow on the peddle. If you rev it, the rpm's build to about 2500 and THEN you can feel/hear the drive train lock up and the speedometer rockets up to about 55 mph, but there is a big delay like something's not catching right away. I'm going crazy over here tryin to figure it out... Please help!!!
    Thanks.
     
  7. imiceman44

    imiceman44 1 ton status

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    Well you have 2 conditions here, the tranny is the one slipping, and the Tcase might have some worn parts or the vibrtion you feel is the chain dragging on the bottom of the tcase.
    Your Tcase is a part time chain driven case, and the chain only works in 4wd.
    If you want to know if it's the chain, put it in 4wd lift the front end and turn the tires back and forth see if there is excessive play and if you here a thug when you hit the stop, meaning you rotate untill you can't and then rotate the opposite direction hard, if it turns more than an inch or 2 and have this thug noise or a chain noise then your chain is worn, needs replacing.
    If not, then you probably have a problem in your tranny, unless you have a hi stall Torque converter, which I doubt.
     
  8. Blue85

    Blue85 Troll Premium Member

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    Sounds like a transmission problem. Check the tranny fluid level. After that, pull the pan and tell us how much metal is down there.
     
  9. foxman

    foxman 1/2 ton status

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    The tranny fluid level is ok and the trany has been rebuilt. no metal in the pan, a little on the magnet. Question though... This noise is happening with the truck in 2 wheel drive, wouldn't that rule out the possibility of it being the chain? and it does have the 3000 stall converter in it. it shifts hard, and the torque converter locks up at erratic times, however, this noise and vibration are coming from the t-case/tail shaft area.. for sure. Is there a bearing or part that wears on these things that are common to go??? what other than bad u-joints and rear pinion bearing (which are all good) is gonna make my truck think it's a vibrator?

    Thanks
     
  10. imiceman44

    imiceman44 1 ton status

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    OK now we're getting somewhere.
    Why in the hell do you want a 3000RPM stall TC?
    do you race it in mud? or deserts?
    Well the high stall explains the hi rpm's before you have the movement.
    About the Tcase, if you grab the driveshaft and try and shake it up and down is there movement? if yes then you have a bad bearing where the slip yoke goes in.
    This is the only part I can think of and it's not uncommon.
     
  11. foxman

    foxman 1/2 ton status

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    I don't know why the guy (the one I bought it from) had the 3000 stall in it, he said it was a "corvette" converter and gave it more punch off the line, and boy, let me tell you, it does. I think it messes up the shift pattern, because of the electronically controoled trans, but anyway, is that output shaft bearing hard to replace? It is probably the case... do I need gaskets? or anything elyse. thanks for the help...

    Jeremy
     

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