Tire sizes on a m916a3

[Timberslinger]

I’m looking at getting an m916a3. I use these trucks for logging. Plan to fit it with some 28” wide floatation tires. The original tires are 425/65r22.5 and the rears are 315/80r22.5. That works out to a 2” diameter difference larger in the front. It’s a 6x6 truck. Always thought the tires had to be the same diameter. I checked other trucks previously sold on GovPlanet and they have the same setup with different size tires. Anybody know what’s up with the difference? Any help would be appreciated.

 

[simp5782]

They wanted a wider steer tire with more load capacity. They are only 1 inch different though When you put a wheel on em. The military does this on several trucks. They did not want super singles in the rear so that was their only option. Some have had 385 65 22.5s on them as well. You can triple wide the wheels in the rear. Weld a Dayton style wheel to a normal 10lug budd wheel. Your studs are already long enough. Put the normal dual wheel on the inside and your welded combo on the outside. Or you can go with 24R21s they are nice and wide

 

[Timberslinger]

So inch difference In diameter does not put unnecessary strain on the u-joints and transfer case? We currently are dualling up the stock super singles that come on the 5 tons. It takes a little fabrication but it can be done. Problem is, the 5 tons don’t hold up to what we use them for. I’ve been trying to find Oshkosh 55000 transfer cases to put in them, but I can’t find those for a reasonable price either. I’ve gone through five transfer cases this year already in those trucks. So now I guess it’s on to the freightliners.

I like the 3 wide idea. What do you do for space between the rims when you weld them together? Or don’t you worry about it?

 

[simp5782]

Would be cheaper to go to the m809 series cases and modify the spray. They are tougher. You wont find many of the oshkosh cases. I put one in my truck and I have a few spares that I will keep. Eastern has PLS cases for 950 but unknown condition.

The Dayton wheel is welded on the inside lip of the outer wheel. It's fine. You just have to assemble it on the truck then air them up.

I would look for a plain on 916. The 400 has more low end grunt over the D60. And the cat has lower gear pairings. I have one for sale in Tennessee.

So inch difference In diameter does not put unnecessary strain on the u-joints and transfer case? We currently are dualling up the stock super singles that come on the 5 tons. It takes a little fabrication but it can be done. Problem is, the 5 tons don’t hold up to what we use them for. I’ve been trying to find Oshkosh 55000 transfer cases to put in them, but I can’t find those for a reasonable price either. I’ve gone through five transfer cases this year already in those trucks. So now I guess it’s on to the freightliners.

I like the 3 wide idea. What do you do for space between the rims when you weld them together? Or don’t you worry about it?

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[simp5782]

So inch difference In diameter does not put unnecessary strain on the u-joints and transfer case? We currently are dualling up the stock super singles that come on the 5 tons. It takes a little fabrication but it can be done. Problem is, the 5 tons don’t hold up to what we use them for. I’ve been trying to find Oshkosh 55000 transfer cases to put in them, but I can’t find those for a reasonable price either. I’ve gone through five transfer cases this year already in those trucks. So now I guess it’s on to the freightliners.

I like the 3 wide idea. What do you do for space between the rims when you weld them together? Or don’t you worry about it?

Dualing up 395s or 1400s only takes a specific wheel found on surplus, a 1/2" spacer and longer studs.

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[Timberslinger]

Dualing up 395s or 1400s only takes a specific wheel found on surplus, a 1/2" spacer and longer studs.

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Here’s what we do for duals. Works well. No spacers or longer studs. Constantly pull 30+ tons of wood not including trailer. Only ever broke one “modified” rim.

 

[Timberslinger]

I just bought an 800 series t case. Trying to figure it out. There are 2 air lines going into what I think are the sprags?? How do I modify them?

 

[Timberslinger]

Just for the record, I know NOTHING about the 809 series t case. I just bought one today. Would like to drop it in one of my 900 series trucks tomorrow, but started reading about sprags..... this is the first one I have seen. I assumed it would be pretty straight forward but now I’m not so sure. Any help would be appreciated.

 

[simp5782]

Just for the record, I know NOTHING about the 809 series t case. I just bought one today. Would like to drop it in one of my 900 series trucks tomorrow, but started reading about sprags..... this is the first one I have seen. I assumed it would be pretty straight forward but now I’m not so sure. Any help would be appreciated.

You will have to get a different output yoke for your allison or for the transfer case since one is a companion flange and the other is a mechanics style.



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[simp5782]

There are also some of the Mk48 Transfer cases available. Not as abundant as the HEMTT cases or as easy to probably configure but it would probably be able to work. However you would not be able to use it on a tractor/dump configuration as it won't allow enough room between the transmission and the front tandem for a driveshaft to be made properly i am sure.

 

[Timberslinger]

You will have to get a different output yoke for your allison or for the transfer case since one is a companion flange and the other is a mechanics style.



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I can do all the bracket and drive line modifications, but what about the sprags? I know nothing other than what I can find on google and SS. I’m gonna open this thing up and see what I can figure out. What I read was that in a nutshell, I have to put air to one side or the other depending on what direction I’m going or I’ll damage the t case. I’ll never be able to get my employees to do that. I could barely get them trained on not backing up in low range. Another logger I work with said years ago he opened one up and welded something to make it full time 6x6, and it ran for years until the truck was completely wore out. He just didn’t remember what he welded. We run on sand and mud all the time. Very little time on hard ground. And usually never over 20mph. Loaded we’re usually in the 4-8mph range.

 

[Floridianson]

Don't know about welding something up. On the 809 series transfer case the air cylinder / rod is in reverse sprag when it is pushed in towards the transfer case. Pulling it out will be forward. If you use the air cylinder then yes it has to have the full amount of truck psi air to keep it in gaged. If you did a manual leaver then just all in or all out. The cylinder piston has a spring on both ends and that is why you need the air to keep it fully in gaged.

 

[simp5782]

There are several old threads on here about welding the sprag up but no pics of it being done.

So basically my understanding is that you are going to 809 series cases cause your workers are breaking 939 cases since they can't follow instructions printed on the dashboard? well then they could probably screw up an Abrams if that is the case cause they can't follow directions and it will not matter what transfer case you put in there. That is the weak link at the moment so if the T138 is stronger than the T1138 the next weak link will show up. more than likely the tailshaft on the allison.

There are several Oshkosh 55000 series transfer cases available on the civilian markets as well for around $1500 but like i said on a tractor/dump truck you will run into flange and yoke issues along with driveline lengths that can not be accomplished on the NHC250 platforms in the SWB trucks.

 

[Timberslinger]

The last 3 have split pulling a load straight ahead. I’ve been looking for a 55000 but haven’t been able to find a reasonably priced one with a known history. I’m planning on picking up an m916 Monday. It has 98 miles on it. I’ll see if that holds up. In the mean time Im just trying to get the 5 tons a little more reliable. i appreciate the help.

 

[Special T]

Timberslinger what size/kind donor wheel did you use for those home made duals? Were they 22.5 or 24.5 tubeless?

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[Special T]

What kind of wheel did you run on the inside?

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[tobyS]

I had my T138 apart and found it had been installed in the 817 recently (now sold), apparently a new one. But it made a heck of a racket at 30 mph. I found that yes it was new, but all three shafts had not had the bearings set and the output shaft could move up 1/8". Just saying... check to see there is a light preload, starting on the input shaft and going to the middle and output. Don't simply throw a NOS in.

Oh yea...there is a different gear ratio on the front output and the rear output of the T138. I can't recall the ratio but the back is always trying to over-run the front and the Sprag relieves it in whatever direction, forward or reverse. Welding locks in that gearing difference and will break rather soon.

Edit...I guess welding could be the axle pig....which for timber I would do on the rears or one axle if lockers were too pricey.

 

[Timberslinger]

For the outside I used a regular 14r20 rim, and cut the spider out. On the opposite side of the same rim I welded the spider and lip from a 22.5 stud piloted trailer wheel. Then took the spider I cut from the 14r20 and using it as a 1/4" spacer, put it on the hub first, then a regular 14r20 wheel backwards, and finally the modified rim and wheel on the outside. Weve been using them on 3 trucks for over a year, running 80 lbs on the inside, 50lbs on the outside, only cracked 1modified spider. Hauling 30 tons more or less on a log trailer.

 

[Special T]

For the outside I used a regular 14r20 rim, and cut the spider out. On the opposite side of the same rim I welded the spider and lip from a 22.5 stud piloted trailer wheel. Then took the spider I cut from the 14r20 and using it as a 1/4" spacer, put it on the hub first, then a regular 14r20 wheel backwards, and finally the modified rim and wheel on the outside. Weve been using them on 3 trucks for over a year, running 80 lbs on the inside, 50lbs on the outside, only cracked 1modified spider. Hauling 30 tons more or less on a log trailer.

Forgive my ignorance what is the spider?

Is it the center disk of the wheel?

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[tobyS]

Yes, spider appears to be the wheel center.

In case you want to go to the 425 Mich XZL tires on 22.5 rims on the back, I would possibly sell them (4) from my M322 (trailer in classified). If I can't sell the trailer, I hope to go shorter duals.