My truck scales out at 28780 with both tanks full.
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M923 Transfer Case upgrade to Oshkosh 55000
- Thread starter simp5782
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big block 88
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No winch on her still correct?
There is a winch in the bed. A 45k off a 916.
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That is a 3126 off a Genset that belongs to another member.
Fitment and mount type pics. 1/2" plate. Bolting to the transfer case I am only going to use 2 of the bolt holes . It should be fine with 5/8" bolts and the transfer case doesn't twist that much under torque. 1/2" x 8" x 4" plate on the transfer case mount. 14-3/8" from front to rear of the mount inside. Top brace is 3" wide and the bottom is 5" wide. This will be the drivers side mount. I plan on using a stronger type mount on the passengers side since it will be about 8 inches from case to the side original mount placement. So some beefup is in order. Probably be a mated box mount. I am sitting it off to the drivers side to help with all the driveline angles since they all sit to the drivers side.
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In. Took a good bit to get everything welded up today. About 2 dozen 7018 and 7024 rods. The bolts and steel will break before the welds do. I think I am going to unbolt the passengers side bracket and move it forward to center on the transfer case bracket. In the event of going back to a 5 ton case atleast it will be easy to realign. Case will sit about 1 inch higher given the mount bushings I have . I will have to raise the spare tire carrier another inch or two as well. Not a big deal. It bends. HA! Bed will have no clearing issues with the 4x4 under it. I will have to swap the driveshafts out between my front tandem/transfer case and the jackshaft i had. The back mounting bracket on the transfer case is 21-3/4" from the crossmember that holds the receiver dryer. Only 1 bolt on each side is holding the mounting bracket on since they are sandwiched to the case no sense in having to bend them back out much
The passengers side mount on the transfer case is mounted 2 inches higher than the support plate on the drivers side being that the in frame mounts are different frame heights. I will have to remove the case to drill the mount holes for the brackets. they are sandwiched on pretty good.
The passengers side mount on the transfer case is mounted 2 inches higher than the support plate on the drivers side being that the in frame mounts are different frame heights. I will have to remove the case to drill the mount holes for the brackets. they are sandwiched on pretty good.
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big block 88
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Could be angle but the transfer looks lower than the toploader input. I know that an inline shaft is a no no but if you have oposing angles either poisitive or negative would be fine i would thinm.
It is for now. The mount bushings are 1.5" thick and aren't installed yet The rear shaft angle out of the transfer case will be slightly to the passengers side going to the diff. The front axle output on the transfer case is direct in line with the rear axle output so you can see the line angle from the underside photos
big block 88
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Roger that. Makes perfect sense.
big block 88
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Im no driveline expert but it sure looks to be a nice offset. Looks nearly stock
Completed. Total cost including transfer case, oil, steel,bolts, 2 U joints, two 4x4x12s, and reamer bits $350. About 10 man hours total into it of solid work.
Used 2 tractor drivershafts that go from the transfer case to the front tandem. Replaced the u joints with some moog. The other one I left alone. All joints are the 280X equivalent Would like to upgrade all of them to that style joint eventually. Just get rid of the companion flanges all together. Used the same transfer case bushings at the T1138 just ground them down to flat. The top of the transfer case clears by about 3 inches. Lower part of the case is higher than my larger fuel tank but i may invest in a rock guard. Runs well down the road. 50mph at 2000rpms in 15th (direct). Posted by RPMs/mph for 13-16th gears. For sure geared lower. I put it in R1 and it dug out of the sand it was sitting down in pretty much at idle on its own with a empty trailer hooked to it. I will monitor the transfer case temps on the next trip. Yeah I am going to lose some higher speed but the T1138 will not handle a bigger engine and it's power. Especially not with a transmission that is 95% efficient in front of it.
Transmission to Transfer driveline is raised by 3 inches. I had to cut the spare tire carrier to make the clearance. It just would not go up high enough. Not like I use it anyway. Output to front tandem shaft angles up almost 2inches and a 1.5" offset. This should be fine as the shaft has plenty of room for toward travel as well as upwards. I will figure the front driveline out after the big cam swap since I will be moving that cross member under the truck as well as using some HEMTT driveshafts instead of the 939s.
Used 2 tractor drivershafts that go from the transfer case to the front tandem. Replaced the u joints with some moog. The other one I left alone. All joints are the 280X equivalent Would like to upgrade all of them to that style joint eventually. Just get rid of the companion flanges all together. Used the same transfer case bushings at the T1138 just ground them down to flat. The top of the transfer case clears by about 3 inches. Lower part of the case is higher than my larger fuel tank but i may invest in a rock guard. Runs well down the road. 50mph at 2000rpms in 15th (direct). Posted by RPMs/mph for 13-16th gears. For sure geared lower. I put it in R1 and it dug out of the sand it was sitting down in pretty much at idle on its own with a empty trailer hooked to it. I will monitor the transfer case temps on the next trip. Yeah I am going to lose some higher speed but the T1138 will not handle a bigger engine and it's power. Especially not with a transmission that is 95% efficient in front of it.
Transmission to Transfer driveline is raised by 3 inches. I had to cut the spare tire carrier to make the clearance. It just would not go up high enough. Not like I use it anyway. Output to front tandem shaft angles up almost 2inches and a 1.5" offset. This should be fine as the shaft has plenty of room for toward travel as well as upwards. I will figure the front driveline out after the big cam swap since I will be moving that cross member under the truck as well as using some HEMTT driveshafts instead of the 939s.
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silverstate55
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Wes, that's amazing! I'm so happy that the transfer case made it out to you!
Good job!! Can't wait to see the BC swap.
Good job!! Can't wait to see the BC swap.
Well I took her out and stretched her legs for a 2,800 mile journey with the new transfer case. Overall the power to the ground is well noticed. Overall speed with an empty trailer is around 62mph at 2100rpms and a little over 9mpg. Loaded with a 925 on the trailer mileage was around 6.5mpg and averaged 58mph over a 1230 mile haul. Granted this speed isn't that high but given the terrain across Missouri as well as western PA it did not fair to bad. Along with the horrible roads in indy and ohio. It did feel nice to pass a Indiana national guard convoy with little effort.
No noticeable vibrations. I did not like the temperature on the input bearing that the transfer case had but after thinking about it, eh not so bad. It has a temp of around 180 or so. Pump temp is around 140 to 155 depending. I was running straight 40 but i switched out to 40 synthetic and it did drop the temp. However thinking about it, I honestly bet an HET towing an Abrams has a higher input bearing temp than 180 running down the highway. So I will just monitor it. I may just add a cooler to it and be done with it.
In the market now for a PTO for the transfer case if i can even find a part number.
Overall though. Even loaded at 62,000 take off in 7th and 8th gear is easy with no bog. Hits 1100rpms within a second. Even at that weight it will easily jump the 2 gears on the CAT all the way 8 to 16 and have plenty of power. And it will break the 1600s loose on pavement in 6th gear so it is pretty efficient on its power distribution. The CAT 7155 is 95% efficient according to the tests.
https://youtu.be/P_DpaefcFbo
No noticeable vibrations. I did not like the temperature on the input bearing that the transfer case had but after thinking about it, eh not so bad. It has a temp of around 180 or so. Pump temp is around 140 to 155 depending. I was running straight 40 but i switched out to 40 synthetic and it did drop the temp. However thinking about it, I honestly bet an HET towing an Abrams has a higher input bearing temp than 180 running down the highway. So I will just monitor it. I may just add a cooler to it and be done with it.
In the market now for a PTO for the transfer case if i can even find a part number.
Overall though. Even loaded at 62,000 take off in 7th and 8th gear is easy with no bog. Hits 1100rpms within a second. Even at that weight it will easily jump the 2 gears on the CAT all the way 8 to 16 and have plenty of power. And it will break the 1600s loose on pavement in 6th gear so it is pretty efficient on its power distribution. The CAT 7155 is 95% efficient according to the tests.
https://youtu.be/P_DpaefcFbo
welp shes busted apart. Looks pretty simple. The rear bearing retainer there has a adjustment for play. She had a noise when you would let off the throttle after 40mph. nothing below that. Was driving along and I guess it locked up hard enough to throw the driveline. I have some noise in the output rotation area. Center gear looks fine and I have some bearing roughness when i spin em with their races on. I did have some small needle bearing material in the oil. I did have some roughness of the needle bearing and the low range gear on the input shaft. Came apart pretty easy in about 10 minutes.
No gears have any cracks or chips and no shafts look to have any damage so I will dismantle it and replace all the bearing and races and the needle bearing and retainers under the gears and put it back together.
https://www.youtube.com/watch?v=x7D10uX_F88
No gears have any cracks or chips and no shafts look to have any damage so I will dismantle it and replace all the bearing and races and the needle bearing and retainers under the gears and put it back together.
https://www.youtube.com/watch?v=x7D10uX_F88
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Bearings just go out. I had an issue when i first got it in which the Input bearing temp would get pretty hot. Sometimes 250 to 270 degrees towing around an empty trailer. Oshkosh assured me that a HET towing an Abrams would hit 300 or more degrees and it was meant for it. I think the front input bearing wasnt in good shape from the get go or the pump was weak or may have had a blockage I did find a piece of plastic that looks like a retainer in the case. it was decent size so maybe it had a restriction on the pump feed. No telling.