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Harsh knock when letting off gas...NP205

Discussion in 'The Garage' started by wy4tt, May 15, 2005.

  1. wy4tt

    wy4tt 1/2 ton status

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    I just got the NP205 in, with a new driveshaft. This is coming from a 203. So, when either going from no throttle to moderate throttle (in low rpms) or from moderate throttle to no throttle, there is a pretty bad knock. Also does it going from park to reverse or from reverse to drive. It does it in either 2H or 4H. Please note that I don't have a front driveshaft on yet. Could this be part of the problem? I'm almost positive it's coming from somewhere near the transfer case. Feels like there is slack there but I can't isolate the problem. Also, it has a rebuilt t350. The new driveshaft has spicer yoke etc. and the 205 has new seals and hardware as well. By the way, there was no such knock with the 203. Maybe it's normal, but it sounds a little excessive to me and I don't want to ruin any of these new parts! Thanks for any insight.
     
  2. RustBuket

    RustBuket 1/2 ton status

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    New ujoints as well? Could be diff gears giving up.
     
  3. wy4tt

    wy4tt 1/2 ton status

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    Yep, new u-joints as well. Pretty much everything is rebuilt or new. When in park and no pressure is on the drivetrain, I can roll the driveshaft back and forth about half an inch or so. The clank seems to come from the area between the txfr case and trans. My buddy's does it as well (mostly same setup) but his driveshaft doesn't have quite as much slack in it. Maybe it's normal?
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I'm going to guess you have a bad drive sleeve. They pretty commonly wear out the splines which would give you a clunk sound when getting on or off the gas.
     
  5. wy4tt

    wy4tt 1/2 ton status

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    Thanks for the replies guys.
    4x4High, is the drive sleeve an expensive replacement? I'm not sure what it is. It's in the txfr case? Also, can driving it like that cause damage to other hardware? Thanks again. I'm new at this, so your advice is a big help.
     
  6. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    the drive sleve is what connects the transmission output shaft to the transfercase input shaft. this was also the same thing i thought of after reading your post.

    i think you can get a new one for around $75, sometimes ive seen them on ebay for $50 or less.
     
  7. FWP

    FWP CRS

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    Did you replace the 203 with a 205, or did you do the doubler thing? What else did you change besides t-case config?

    FYI, the 205 has ALOT of gear slop. If there is ANY driveshaft angle issues, you WILL hear it in the 205.
     
  8. wy4tt

    wy4tt 1/2 ton status

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    Replaced the 203 with the 205, no doubler. Had the 205 setup for a t350. It already had a 4" lift. The entire driveline is pretty much replaced (14ff, D60, driveshaft, etc.) As I mentioned before, there is no front driveshaft on right now.
     
  9. TrcksR4ME

    TrcksR4ME 1/2 ton status

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  10. FWP

    FWP CRS

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    Ah, so now your driveshaft is longer right? The 205 is much shorter than the 203. That means your driveshaft angles changed. Might want to look into it.
     
  11. wy4tt

    wy4tt 1/2 ton status

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    It's longer. It fits snug. The slop sounds like it's between the trans and the 205, apparently where the drive sleeve is. It's not on the rear of the 205, u-joint, etc. Not sure if that has anything to do with the angle or not though.
     
  12. FWP

    FWP CRS

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    Rob(therobzilla) and I have been through hell a couple years ago trying to figure out the cause of the 205 case noise (similar to what you describe). It's the wierdest damn thing, you can have perfect parts throughout the drive train, and it still makes racket. Driveshaft vibration at or near coast would transfer into the 205 gears. The solution was a rear CV driveshaft.

    In searchin for the Solution, I found an old post on Pirate, in which Jess (HAD) replied, saying gear slop and bad angles. Too bad I skipped right over it, I should have payed attention, it would have saved Rob an I whole bunch of headaches.

    Good luck!
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    27 spline is going to be much stronger than a 10 spline, so realistically it should have much less wear over the same period of time/use.

    Drive sleeve is still a dumb idea IMO (and GM's apparently, since they quit using them later on in production) but if you have one, I'd not worry nearly as much about a 27 spline one as I did my 10 spline.
     
  14. garlicbreath

    garlicbreath 1/2 ton status

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    It's prolly ok, but have you gone back and retightened all the crossmember and t-case mounts?
     

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