Transmission swap question

[Olly]

I was thinking about swapping out my transmission in my XM818 to a Fuller 10 speed. Was wondering if it would mate up to the NHC 250 Cummins, or if there would be any clearance issues or anything like that? Would the stock clutch pedal work, would there even be enough room between the trans and the transfer case....would the front driveshaft have enough clearance? Any input would be appreciated or suggestions for other trannys that would fit..... Liked the idea of the 10 speed but it's not set in stone yet.
Thanks

 

[Brutacus]

The Fuller 10 speed is a great transmission, but it is a wide transmission. It can bolt to the back of the engine if you find the correct bell housing. If you search, the part number should be on a couple of threads here. There would definitely be clearance issues with the air pack. The drive shaft to the front axle might have to have an offset carrier bearing to clearance the transmission. You also wouldn't have any room on your passenger side for a pto. I have looked into the swap for my M818. Have you thought about an Eaton FSO-8406A 6 speed. They will fit for sure. Check this out for other Eaton transmissions https://www.eaton.com/EN/rr/ProductsServices/ProductsbyCategory/Transmissions/PCT_486870

 

[Olly]

The Fuller 10 speed is a great transmission, but it is a wide transmission. It can bolt to the back of the engine if you find the correct bell housing. If you search, the part number should be on a couple of threads here. There would definitely be clearance issues with the air pack. The drive shaft to the front axle might have to have an offset carrier bearing to clearance the transmission. You also wouldn't have any room on your passenger side for a pto. I have looked into the swap for my M818. Have you thought about an Eaton FSO-8406A 6 speed. They will fit for sure. Check this out for other Eaton transmissions https://www.eaton.com/EN/rr/ProductsServices/ProductsbyCategory/Transmissions/PCT_486870

Thanks for the response and the info. Hadn't actually thought about that do you know if the shift points between 4 and 5 are better than on the stock transmission? Basically just want a reliable more user friendly transmission but still want to retain the 6 wheel drive without having to do any crazy modding. Also thought I don't have a pto right now would like to keep that option available.

 

[Brutacus]

Thanks for the response and the info. Hadn't actually thought about that do you know if the shift points between 4 and 5 are better than on the stock transmission? Basically just want a reliable more user friendly transmission but still want to retain the 6 wheel drive without having to do any crazy modding. Also thought I don't have a pto right now would like to keep that option available.

The shift points for the 6 speeds and the 10 speeds are much better. On the spicer 5 speed transmission, there is a 78% jump between 3rd and 4th gear which is a WIDE gap. It really needs another gear in there to fill up that hole. The gap between 4th and 5th gear in the spicer 5 speed is about 28% which is pretty good. In the 6 speed eatons, the gap between 4th and 5th gear ranges from 59% - 37% depending on which model you have which is good, and the 10 speeds it's about 35% to 38%, which is even better. Everyone who has an M809 series truck has noticed the missing gear in between 3rd and 4th.

 

[Olly]

The shift points for the 6 speeds and the 10 speeds are much better. On the spicer 5 speed transmission, there is a 78% jump between 3rd and 4th gear which is a WIDE gap. It really needs another gear in there to fill up that hole. The gap between 4th and 5th gear in the spicer 5 speed is about 28% which is pretty good. In the 6 speed eatons, the gap between 4th and 5th gear ranges from 59% - 37% depending on which model you have which is good, and the 10 speeds it's about 35% to 38%, which is even better. Everyone who has an M809 series truck has noticed the missing gear in between 3rd and 4th.

Thanks for that info as well.... probably will be going with the six speed so I don't have to modify the truck. It's good to know that it'll get rid of the gap between third and fourth.

 

[msgjd]

Thanks for that info as well.... probably will be going with the six speed so I don't have to modify the truck. It's good to know that it'll get rid of the gap between third and fourth.

A town highway dept near here put a 13-speed in a M813 they had a commercial dump box on. I inspected their work. It's quite an involved project if you want to retain 6x6 capability as they did. Booster pack was relocated due to tranny width, transfer case remounted further back to accomodate tranny length, and the front, stub, and rear-forward driveshafts each had to be custom built to fit. Some mounts also had to be custom built. There was also another issue with having things line up but I don't remember what it was. Maybe it was about the location of the shifter. Whatever it was, the engine had to be moved forward, which required the removal of the stock fan. They had to install electric fans in front of the radiator, the only room that was left.

If you don't need an active front axle, the conversion to a fuller 9sp, or 10 or 13 or 18 would be less involved as you would permanently remove the transfer case, stub shaft, and front driveshaft. The rear-forward driveshaft would need to be extended, the booster pack relocated, and there is still the possibility your shifter will not come up thru the floor in the right place.

I've not seen any 6-speed conversions, thus I cannot comment on those.

This is the converted truck :

 

[MyothersanM1]

The Fuller 10 speed is a great transmission, but it is a wide transmission. It can bolt to the back of the engine if you find the correct bell housing. If you search, the part number should be on a couple of threads here. There would definitely be clearance issues with the air pack. The drive shaft to the front axle might have to have an offset carrier bearing to clearance the transmission. You also wouldn't have any room on your passenger side for a pto. I have looked into the swap for my M818. Have you thought about an Eaton FSO-8406A 6 speed. They will fit for sure. Check this out for other Eaton transmissions https://www.eaton.com/EN/rr/ProductsServices/ProductsbyCategory/Transmissions/PCT_486870

This intrigues me as I really dislike that lag between 3 and 4, but it raises several questions...

1) What output companion flange do you use as the mainshaft splines are different?
2) Does the PTO and associated linkages bolt up to the right side without modification?
3) How would one modify the poppet valve actuation for shifting the sprag cylinder?

 

[Brutacus]

Common flanges are available for the eaton six speeds. I've seen them on the trucks at work, I don't know what the part number is though. If one can't be located, I suppose a drive shaft shop would be able to fab something together. I'm sure the PTO linkages would have to be modified, as well as the length of the drive shaft for the winch. Probably would have to make the linkage rods a little longer/a little shorter because the location would be off a little from the stock position. As for the poppet valves for the sprag, I'm looking into getting new gears cut so I can eliminate the sprag/poppet valve setup. I suppose you could switch transfer cases over to the T-1138 also. I'd be a little wary of that because some of those six speeds have 9 to 1 ratio first/reverse gear. Anyways the 6speeds vary in length from 20 inches to 28 inches long and can handle up to 820 lbs-ft. of torque. I don't know how tall these are compared to the spicers. They don't look like these would require much modification to the floor of the M809 cabs, just relocation of the hole for the gear shifter. More modifications needed if the transmission is taller.

 

[MyothersanM1]

Common flanges are available for the eaton six speeds. I've seen them on the trucks at work, I don't know what the part number is though. If one can't be located, I suppose a drive shaft shop would be able to fab something together. I'm sure the PTO linkages would have to be modified, as well as the length of the drive shaft for the winch. Probably would have to make the linkage rods a little longer/a little shorter because the location would be off a little from the stock position. As for the poppet valves for the sprag, I'm looking into getting new gears cut so I can eliminate the sprag/poppet valve setup. I suppose you could switch transfer cases over to the T-1138 also. I'd be a little wary of that because some of those six speeds have 9 to 1 ratio first/reverse gear. Anyways the 6speeds vary in length from 20 inches to 28 inches long and can handle up to 820 lbs-ft. of torque. I don't know how tall these are compared to the spicers. They don't look like these would require much modification to the floor of the M809 cabs, just relocation of the hole for the gear shifter. More modifications needed if the transmission is taller.

View attachment 777734

All those issues I guess are doable.

-The sprag can be shifted electro-mechanically through the reverse light switch with a 4-way valve.
-PTO linkage and drive shaft could be "cut-and-pasted". Question though...would the OEM PTO be compatible with a Fuller Eaton transmission?
-Some crafty sheet metal work on the cab tunnel would be in order, as the shift lever would sit farther back.

After some studying, it appears one would have to replace everything from the flywheel back including the whole clutch assembly, release bearing, bell housing so on and so forth. Am I right in this observation?

 

[Brutacus]

All those issues I guess are doable.



After some studying, it appears one would have to replace everything from the flywheel back including the whole clutch assembly, release bearing, bell housing so on and so forth. Am I right in this observation?

Yes, you are correct in these observations. I know a different bell housing would be required as the spicer bell housing will not bolt up to the eaton transmission.
I don't know if a different clutch disc, spring plate, throw-out bearing, and linkage would be needed. If a bell housing with the same dimensions as the spicers, with the same depth, SEA 2 pattern, and the clutch linkage in the same location is available, one might be able to re-use some of the stock equipment. The input shaft on the six speeds are 1.75", but can be changed over to 2" and 1.5" in varying legnths which would also be helpful in using the stock clutch equipment. My observations would be, if the input shaft, and bell housing were the same dimensions as the spicers, then it could be possible to re-use the stock clutch components with 6speed trans. If it's cheaper, or at least more common parts (easier to obtain) then new clutch disc, spring plate, etc. might be better anyways. My preference would be to use a bell housing that keeps the dimensions as close to stock as possible. After that is found, then get clutch components that fit it.

 

[74M35A2]

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.

 

[Brutacus]

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$.

 

[MyothersanM1]

The FSO-8406A specs out to handling an input of 827 ft. lbs.
The NHC250 specs out at 685 on the output.

 

[Brutacus]

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.

 

[MyothersanM1]

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.
View attachment FSO-8406A Specs.pdf

 

[Brutacus]

Here's where I got that number from. It's in Newton meters so I converted it.
View attachment 778274

I have seen that, but I never converted the Nm to ft-lbs. My source is the https://www.eaton.com/EN/rr/ProductsServices/ProductsbyCategory/Transmissions/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.

 

[MyothersanM1]

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.

 

[Brutacus]

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.

 

[74M35A2]

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.

 

[MyothersanM1]

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"...View attachment 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...View attachment FSO-8406A Specs.pdf
Post #25 indicates 28" on the Spicer...https://www.steelsoldiers.com/showthread.php?64336-Spicer-5-Speed-in-an-A3/page3

The wing type yoke...
https://www.finditparts.com/products/221115/dana-holding-corporation-640480013



In Re: The PTO

PTO drives off the overdrive gear on the countershaft.

Page 14 for Fuller drive gear specs...View attachment 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&originalsearchtext=7409588