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np205: 10 splines vs. 27 spline

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mike reeh, Jan 25, 2002.

  1. mike reeh

    mike reeh 1/2 ton status

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    the only differences between the 205 from a sm465 and a th350 are the input shaft splines right? (as far as tranny mating goes) .. well assuming I have the adapters, all I would need to use a 10 spline 205 on my th350 is the coupling sleeve right?

    well how rare are these beasts? I tried asking a guy at advance adapters about it but he gave me useless information as a response, and didnt answer my question as to what comes in the $300 kit to use a 10 spline 205 on a th350.....

    so Im assuming its just the spline count. Does anyone besides AA make the couplers? Is taking apart both cases to swap input shafts an option? Ive got all the stuff im talking about laying around in the shop but I dont have the time lately to just start tearing stuff apart and i know you guys have been there done that.

    the thought of having a custom sleeve made has even crossed my mind but Ive talked to a couple machinists and they said to make internal splines is very pricey!! one guy said $180 an hour with like a 2 hour minimum :( .....

    the reason im asking all this is that the th350+np205 adapter and case I have is from '73 and its been in a wreck, while I have another pristine '77 np205 but its 10 spline.. it shifts better and is really low mileage.. Id really like to run the newer one even if it is going to end up costing me a couple hundred......

    thanks for listening!!

    mike reeh
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Hit to ORD forum and ask Stephen. He's going to know what it takes.

    Women dig dents and flat paint!
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  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I think you can swap the 27 spline input gear into the 10 spline 205 with no problems. I know the 32 spline input gear requires some simple maching to do the swap...maybe the 27 is a straight swap? Then you can use the better (low mileage) case behind the TH350.

    Rene

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  4. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    27 and 10 spline interchange directly, same input bearing. They both use the "small" bearing where the 32 spline uses the "big" bearing.
    Basically 3 things have to be present and right to mate a 205 to a transmission:
    1: input gear must match trans spline count, TH350/TH700 use 27, SM465 uses 10, TH400 uses 32
    2: drivesleeve must be correct spline count, obviously if it's going to couple the shafts, it needs to match! Only the SM465 and TH350/TH700 use a drivesleeve, TH400 is a direct connection from output shaft to input gear.
    3: adapter housing must match the cases being bolted together.

    AA has a kit to do just about anything but they generally make very little use of factory parts. They'll leave a 10 spline shaft in the NP205 and have you change the transmission output rather than taking the 205 apart, which is a simpler job by far.
    If you have all the parts you should be able to mix and match to get the TH350 bolted to the NP205, if not we do carry the inputs, drivesleeves and adapter housings to make it work.
    We've also looked into the coupler with different internal splines but price is what it comes to. And the fact that the 10 spline isn't as nice a connection as the 27 spline. Comparable strength and more splines are the criteria there.

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  5. mike reeh

    mike reeh 1/2 ton status

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    GOOD TO HEAR!!

    One other thing i noticed was that the 27spline 205 that I DIDNT want to run was a yoke-type front driveshaft and I dont have any front shafts like that....... I personally like the flange style better and thats what Ive always had. what do you guys think? Is there a benefit to either/or ?

    It looks as simple as removing the nut and swapping "yokes" except that little aluminum cover that holds the seal are different castings.. I didnt bust out the calipers to take any precise measurements though......

    thanks a million steve, and others.

    Its also good to know that now that I have the 27 spline input, if the T-Case ever explodes, I can just find another 10 spline one which are dime a dozen (and i think i have about 3 of em sitting around) to replace/fix it.........................

    Ill take some pics of the "swap" and let you all know how it turns out. good day

    mike
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The flange front output 205's are stronger...by how much I'm not sure though.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
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