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Thread: Transmission swap question

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    4 Star General 74M35A2's Avatar
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    I think the input torque rating of those single shaft 5 and 6 speed Eaton FS series boxes are relatively low? Have you guys compared that to the torque rating of the engine you want to put in front of it? I had one as a 5 speed and could not even sell it for $100, even on here. Scrapped it for like $13. Everybody wanted the overdrive 6 speed.

    You guys know I'm more of a turbo medium duty engine guy (8.3L), but I think those 855's have some serious low end grunt to them, (that I definitely don't have). Would hate to see you do all the work to convert, and it breaks.
    CFO @ Portacharger

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    The transmission I suggested, and interested in is the FSO-8406A with a capacity of 860 lbs.-tq., a 6 speed with over drive. The FS-7206A, FS-8206A are direct drive transmissions, but have a different case with a passenger side 8-bolt PTO drive. Those are more than enough for the nhc250, and is still skinny enough to fit in there. Now if you throw a turbo on it, or switch over to a more powerful Cummins 270, 290, etc. and up, I can't say as I don't know what the torque ratings are for those stronger engines. I don't know about the Eaton 5 speeds, I never looked at them. Hate to hear you had to scrap a good trans for 13$.

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    The FSO-8406A specs out to handling an input of 827 ft. lbs.
    The NHC250 specs out at 685 on the output.
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    Quote Originally Posted by MyothersanM1 View Post
    The FSO-8406A specs out to handling an input of 827 ft. lbs.
    The NHC250 specs out at 685 on the output.

    My source lists it at 860 lbs-ft. of torque. Hmm... still though, that's plenty for the nhc 250. Does any one know what the torque specs are for the Spicer 6453 for a comparison? I know it can handle the nhc 250, just wondering.

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    Quote Originally Posted by Brutacus View Post
    My source lists it at 860 lbs-ft. of torque. Hmm... still though, that's plenty for the nhc 250. Does any one know what the torque specs are for the Spicer 6453 for a comparison? I know it can handle the nhc 250, just wondering.

    Here's where I got that number from. It's in Newton meters so I converted it.

    FSO-8406A Specs.pdf
    Brian McMahon, SPC, USA (Ret.)
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    '77 AMGeneral M818 5 Ton Tractor, "Hannibal 8"
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    -M923 Dropside Bed Installed
    -Converted to full dual circuit Air Brakes
    Only in my memory, always in my heart:
    XM-1, M-1, IPM-1, M1A1 Main Battle Tanks
    M998 HMMWV 1 1/4 ton
    ELA: 0162-0209


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    Sergeant Major Brutacus's Avatar
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    Quote Originally Posted by MyothersanM1 View Post

    Here's where I got that number from. It's in Newton meters so I converted it.

    FSO-8406A Specs.pdf
    I have seen that, but I never converted the Nm to ft-lbs. My source is the https://www.eaton.com/EN/rr/Products...ons/PCT_486870 link. Did you notice the gear ratios for the FSBO-9406A? I know it is an auto shift (manual shift with an X-Y axis shifter), but that has the best gear ratios to compare to the spicer 6453 transmission. If it could be had with just a manual shifter only, it would be the ideal replacement for the M809 series. That trans fills in the hole in-between 3rd and 4th.

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    I have been really studying the prospect of swapping to a Fuller 6 speed. I have found a compatible clutch bell housing, output yoke and a viable way to shift the transfer case sprag. The Fuller and Spicer appear to be very close in length with negligible differences; i.e. shifter location, jackshaft length.

    However, it appears that the OEM PTO is not compatible with the Fuller transmission drive gear.

    Fuller transmission drive gear: 7.00P, 26DEG
    Spicer transmission drive gear: 5.38P, 17.5DEG Pres. Angle, 26.1769DEG Helix Angle

    Dana PTO (OEM) drive gear: 6.00P, 17.5DEG Pres. Angle

    From literature I have read these numbers will not mesh properly.
    Brian McMahon, SPC, USA (Ret.)
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    Quote Originally Posted by MyothersanM1 View Post

    I have found a compatible clutch bell housing, output yoke

    Fuller transmission drive gear: 7.00P, 26DEG
    Spicer transmission drive gear: 5.38P, 17.5DEG Pres. Angle, 26.1769DEG Helix Angle

    Dana PTO (OEM) drive gear: 6.00P, 17.5DEG Pres. Angle

    From literature I have read these numbers will not mesh properly.


    What are the dimensions of the bellhousing? The one on the spicers are short. Do you think the one you found keeps the overall length about the same as the spicer 6453's overall length?
    What literature did you source this from? I want to read more on both transmissions. I have mainly focused on the gear ratios, weight, and physical dimensions of the Eaton 6's. I haven't thought about the PTO drives not being compatible. One question comes to mind. Is the drive gear for the PTO a separate gear (idler) that can be interchange for different pto drives, or is it one of the gears on the counter shaft that a driver would shift thru to get to the top gear (gears 1 thru 6). This is interesting.

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    I only know it because I went through it myself.

    Could be a few options on PTO/gear. A different compatible PTO with shaft output should work same? Or, convert to hydro winch drive and use a belt/clutch pump, the 939 hydraulic tanks are very narrow.
    CFO @ Portacharger

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    Quote Originally Posted by Brutacus View Post
    What are the dimensions of the bellhousing? The one on the spicers are short. Do you think the one you found keeps the overall length about the same as the spicer 6453's overall length?
    What literature did you source this from? I want to read more on both transmissions. I have mainly focused on the gear ratios, weight, and physical dimensions of the Eaton 6's. I haven't thought about the PTO drives not being compatible. One question comes to mind. Is the drive gear for the PTO a separate gear (idler) that can be interchange for different pto drives, or is it one of the gears on the counter shaft that a driver would shift thru to get to the top gear (gears 1 thru 6). This is interesting.
    Yes, the fuller bell housing (A-5025) is longer by about 1 1/4"...Fuller Clutch Housings.pdf
    Somewhere on this site there is side elevation drawing of the 6453 with copious dimensions. However, I did not save it and now I can't find it.
    The overall length is a hair under 30" but the yoke in the graphic extends longer than a "wing" type yoke would...FSO-8406A Specs.pdf
    Post #25 indicates 28" on the Spicer...https://www.steelsoldiers.com/showth...in-an-A3/page3

    The wing type yoke...
    https://www.finditparts.com/products...tion-640480013
    Wing yoke 001.jpgWing yoke 002.jpg


    In Re: The PTO

    PTO drives off the overdrive gear on the countershaft.

    Page 14 for Fuller drive gear specs...PTO Guide.pdf

    OEM PTO Specs.
    https://www.parttarget.com/2520-00-740-9588_2520007409588_002224-2.html/-b3e2d75c-4b27-4dfe-907d-540baaf101e7?searchtext=7409588&searchoption=sku&o riginalsearchtext=7409588
    Last edited by MyothersanM1; 10-08-2019 at 21:18.
    Brian McMahon, SPC, USA (Ret.)
    Culver City, CA, USA (of course)
    MVPA Member #33433


    '77 AMGeneral M818 5 Ton Tractor, "Hannibal 8"
    -20K Winch added
    -M923 Dropside Bed Installed
    -Converted to full dual circuit Air Brakes
    Only in my memory, always in my heart:
    XM-1, M-1, IPM-1, M1A1 Main Battle Tanks
    M998 HMMWV 1 1/4 ton
    ELA: 0162-0209


    I bear my allegiance to those...
    Whom willingly swear to the Oath...
    Then pick up a weapon...
    And bravely stand a post.


  11. The Following User Says Thank You to MyothersanM1 For This Useful Post:

    silverstate55 (10-09-2019)

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