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NP205 with excessive play

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mike reeh, Nov 9, 2002.

  1. mike reeh

    mike reeh 1/2 ton status

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    So, I got my th350/np205 setup going... I had a good 77 np205 with a 10 spline input that came on a parts truck and I found a wrecked np205 27spline that I stole the input gear out of and installed in my other np205, so I could run it on my th350 transmission in my 77 K20

    well, there is a lot of play, it clunks when youre driving if you let off the gas and hit it hard, the classic driveline slack... it definately is coming from the np205, and not the rear or front end. The trans->tcase coupler is tight..

    So my question is this: for all you np205 experts, what is causing the play and how can I fix it? I put some heavy gear oil in there to quiet it, and it does help to an extent, but when the case heats up its pretty much back to normal. Is there an adjustment or shim or bearing that can be tweaked? Why would there be that much play in an all gear driven case? It kind of bums me out, my np203s with a billion miles never clunked that much...

    look forward to some ideas! /forums/images/graemlins/ears.gif
     
  2. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    It could be a problem in the rear end, bad u-joint, sloppy drivesleeve between the TH350 and NP205 (common problem), or it could be interal in the case (but I don't really see how unless it is totally worn or the idler shaft has excessive play, but both of those are doubtfull).
     
  3. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Also is the rear output slip or fixed. If it is slip, the slip yoke could be worn.
     
  4. TX Mudder

    TX Mudder 1/2 ton status

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    I doubt it is internal. Yes, it's all gear and more gears equakls more total slop.
    I am not the expert by any means, but I agree about checking the drivesleeve and splines on the input shaft.
    -- Mike
     
  5. therobzilla

    therobzilla 1/2 ton status

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    Mike,

    Just some infor for your quest. I just finished a complete 205 rebuild, and I do mean complete. Had the case stripped down to the bare case. Replaced every bearing seal and shimmed the idler shaft to spec. Guess what, I too still have the "When you let off the gas it has a noise" even after the rebuild. My only thinking is is must be worn gears in the 205. Becasue everything else has been either replaced or correctly rebuild.

    On think I do know is after the rebuild, I'm not worried about the noise anymore. It has to be the wear pattern in the 205 on the gears.

    Just my .02.

    Rob
     
  6. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Do either of you have a locker in the rear?
     
  7. Waxer

    Waxer 1/2 ton status Author

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    I have a locker in the rear 14 bolt. When I swapped in a sm465/np205 I too noticed slop in the driveline when I shifted gears. I didnt notice it when I had the th350/np205 combo. So either its the tcase, or its the fact the auto must have always kept positive force on the driveline throughout the driving range.
     
  8. Waxer

    Waxer 1/2 ton status Author

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    by the way, nice pics on your rebuild. I've ready many articles on rebuilding the 205 and it looks pretty easy. Hardest part being inserting the needle bearings and checking the end play on the idler shaft. Does that sound about right? If you dont mind, I have other questions I'd like to ask via email. Thanks...
     
  9. mike reeh

    mike reeh 1/2 ton status

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    hmm.. wait a week and the replies start pouring in /forums/images/graemlins/rolleyes.gif

    anyways maybe I didnt make it clear in my original post but its not, repeat not the coupler or the rear end. All the ujoints are brand new (as in less than a couple hundred miles) spicer and the driveshaft was just shortened and balanced.

    furthermore I said that heavier gear oil DID have a positive effect, thus concluding the search for the origin of the slop.

    the np205 is fixed-yoke. Gov-loc in the 14FF.

    The more I drive the truck like a sane person (instead of FULL throttle or NO throttle) the less noticeable it is.. under normal gas-sipping driving, its nearly un-noticeable. I think half the reason I was so bothered by it, is that I expected the case to be TIGHT, being a np205 and all. I can definately live with it. What I really need to fix is the slop in the linkage /forums/images/graemlins/smile.gif Now THAT is enough annoyance to make you drive off a cliff. Got a bungee cord keeping slack on the shifter handle for now.

    -mike
     
  10. Sandman

    Sandman 3/4 ton status Author

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    My 205 is pretty sloppy also. Big clunk going into reverse and such. My first 205 was not sloppy. I had the same problem with the linkage. The hardware store had the right size "wave washer" for like 50 cents or something. It worked great.
     
  11. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Feel free to email at Christopher.Balise@bhs.org
    In YOUR case I would say the slop is the locker and YES you will notice it more with a manual than an auto.
     
  12. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    furthermore I said that heavier gear oil DID have a positive effect, thus concluding the search for the origin of the slop.

    [/ QUOTE ]

    Your driveline is a "solid connection" assuming good u-joints, pinion bearings, proper backlash etc. Harmonics (or clunks) can be transmitted from the rear end and sound as though they are coming from the t-case (i.e. two paper cups at the end of a long string acting as a "telephone"). Addind thicker gear oil will absorb the harmonics making them SEEM quieter. Because you put thicker oil in the case and it gets quieter makes you think it is a problem with the case (which it still could be), but that is not a good indicator. Again not saying your case is not sloppy, but I would still check your rear-end, as the thicker fluid in the case is now just dampening ANY harmonics in the driveline.

    Also the Gov-Loc has not been know to be the strongest or most reliable LSD (and has often grenaded after becoming "sloppy"). Just a thought.
     
  13. Waxer

    Waxer 1/2 ton status Author

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    I know my 14 bolt's yoke has a good amount of play, noticed it when I had to change the pinion seal. I was told that is normal for a 14 bolt with a Detroit.
     

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