Simp's Cat 7155 Swap into a M923A1

Coffey1

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And we are all waiting for launch of something someday before we all past over. I am starting to think they are like NASA one day we will get to Mars
 

99nouns

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I am a tree shade fabricator and unless this rain stops I cant get anything done and it has been raining every day for last 3 months in Central FL... We might be competing with Amazon rain forrests this year... We went from "swamp life" to "mow grass everyday"
 

simp5782

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Haven't gotten much done with the rain going on. Also had to make a few trips to get parts. Ended up going to have to swap on my spare cab. The one I was using the cowl has some depression and I don't feel like messing with it in order to get the windshield to seal up. So I got my other cab all painted and the access panel covered up. Installed a MRAP adjustable seat, as well as the shifter. I had to cut the underside of this cab as well to remove the channel runs so it can clear the transmission. I had installed the shifter in the other cab with the drivers seat so you kind of have an idea of what I am looking at.

I also found a 24" x 12" x 12" Aluminum box at northern tool on clearance so I put it to take up the space in the hole to store stuff in. I will probably put it on some wood to raise it up some. I will probably put a map box or two behind the shifter in that area depending on how all the AC and heater hoses fit in. I will probably spray it with some aluminum primer and spray a coat of bedliner on that ugly box.

Also took another step toolbox and cut it and mated it to the original toolbox for battery storage. I am going to put a step on the upper box but it will only be half as wide as the lower step and set further back so it will be easier to climb up and in. It looks close to the cab but at the moment that cab is not sitting level so it has almost an inch of room.
 

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Jbulach

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Got the transfer case installed today along with the brackets it moved back a total of 8.5" I am going to shorten the driveshaft going to the front tandem by about an inch or so...

...As measured from the back of the engine block to the front of the flange is 69 inches. I believe the bellhousing overall's thickness is 6.5". The same as the stock housing. All difference is a 1 vs 2 bellhousing. Transmission overall is 36inches. Plus the flange so say 40 inches total. Still leaves about a 21 to 23inch jackshaft give or take...
Hey Simp, looking back did you actually have to move the transfer case back?
 

simp5782

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Hey Simp, looking back did you actually have to move the transfer case back?
Yes. 8.5 inches. It was going to make it easier to use a companion flange on the transfer case and spicer style on the transmission side rather than fight with the mechanics style joints.

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simp5782

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Well she is sort of in the final stages for a test drive. I have run in to the crap problem of not being able to build air pressure past 60. Go figure. After I chased a few wiring gremlins and just said screw it and bypassed the whole PCB system for starting it was just a long day.

Truck running at 1500rpm idle. all 3 gauges read up to 60. Hold steady. Used the spray bottle. few small leaks but they were tightened down. Closed off both primary and secondary valves. the transmission tanks still only read 60psi. just wont build over that. So tomorrow I am going to install a shut off valve onto the pressure protection valve line that runs to the front I know I have air on it and shut it down and see if that is where the leak is from or what its not building.

The double check valve 7 KN23000 was bad allowing air to get to the suppy port on the air brake valve on the dash and that in turn Is sending air to the inversion valve and to the rear spring brake chambers and it does not drop air when I do that so I am not leaning towards a bad diaphragm plus they were all just replaced 6 months ago.

The Kn23000 is between the supply for the brakes and the spring brake tank. Even a new valve was not letting air get by so I did away with it and let it feed directly into the tank. tank fills up just fine. Air pressure still wont climb above 60. I even checked the air pressure at all ports on the truck. I have air pressure every where. I checked a few of the main ports at the treadle valve and the rear spring brake and it is at 60psi. so the gauges are right. I did pull the governor line off the top of the compressor. but the compressor is pumping no matter what. I have to sit and ponder on this.

Also got the doors on, and new windshield glass put in and all that good stuff. Took the hood off today to paint it and to make the raised mount. I will get it back on tomorrow when I get motivation.

Finished the battery box and installed a half step I will add a step to the fuel tank side so it easier to climb in. That was a before painted pic. It is rhinolined now.
 

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simp5782

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Nothing going on with the governor? Or with the air dryer you installed?
Gov hasn't changed from before and it was fine. Can charge the system with my big compressor and its fine. Going to run thru a few things tomorrow Gov is also recently new from Bendix so who knows.

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Jakelc15

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60 psi is about the secondary cut out pressure. Maybe the valve is installed backwards. When the governor goes bad it usually sticks at 30 psi.
Does it stay at 60 when shut down?

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simp5782

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60 psi is about the secondary cut out pressure. Maybe the valve is installed backwards. When the governor goes bad it usually sticks at 30 psi.
Does it stay at 60 when shut down?

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I didn't remove any valve to install backwards. It bleeds off slowly after an hour or so. It has a few compression fittings that are leaking so I am going to do those tomorrow. I think the second air dryer is causing a conflict since I have it's governor port plugged off. but it doesn't make sense why the other tanks are doing it. I am going to screw with it tomorrow.

I got tired of the pcb and abs wiring crap under the dash that was a birds nest so I bypassed it all and went off inline fuses so that hurt my brain so I didn't have time for this crap to really think about it.
 
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Jakelc15

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I've never seen anything with 2 air dryers before! You may have created a ripple in the space time continuum!
Just unhook the unloader line from the dryer. There should be no air coming from there until the governor hits cutout pressure.

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simp5782

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Figured it out this morning. There was another tractor protection valve up under the dash that the brake handle lines goes to. AFTER the bulkhead point. It then vents out into the engine bay by the exhaust. I guess the handle had a bad valve since it was dumping air even though it was not activated. it was dumping the air right by the open exhaust so yeah no way I was going to hear that with it running. But it wouldn't do it with the air compressor just hooked to it. So I ripped all that crap out and went to a standard system. '

Got some other air line crap figured out. I went ahead and decided to use the feed line for the spring brake tank to T into the other dryer system. then into the transmission tanks. So I have a dryer, wet tank, then another dryer and wet tank, then a regulator and mister so it should be fine on keeping moisture out. I ALSO did it this way since the air dryer has a one way check valve in it air can't back flow causing the trans tank pressures to drop below 60 and the trans to go into neutral during hard braking if the spring brake and other tanks drain. I am working on installing a gauge setup for that tank system.

Seat and shifter installed and got the dashboard back together.

I also had to add a 1/2" spacer to the spare tire carrier bracket on the drivers side so it is angled up. Otherwise the U joints off the transmission would have been smacking it.

8th gear start off test.

https://www.youtube.com/watch?v=eYkLuyOY4T4
 

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simp5782

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Welp. She is up and going. Went on a test drive today. just 8,9,10. Drove fine. Was pretty quick during takeoff in 8th. Did not do much driving since it does not have exhaust on it yet and we all know a NHC will kill every mosquito in 2 square miles at idle. That is the final step. I got a shop I am trading off some work to do my exhaust for me, rather than me cuss at it all day.

I know I wont be using 1st gear. Even with the spring brakes on I dropped it to first and it tried to take a run with the tires locked. So we wont be using that even loaded to the hilt.

Got the hood raised. Went with two 1/2" pieces of steel under the center mounting point. Then I added another 1 inch spacer under the cross mount beam section on each end and bolted it back down. Yeah hoods are a nightmare.

Got everything else done for the most part with the exception of a few small things. AC charged. Transfer pump wired in, just junk. I did raise the AC unit up higher in the truck so that I have a little more room to shift. That is with the air ride at full height. It feels good with the shifting. Just some getting used to.

I have a rattle from the starter area and I can hear the starter spin when I shut the truck down. I have the gear reduction starter on it however the nose cone on a M915 series starter is 1 inch shorter than the nose cone on a 939 starter. M809, 939, and 915s all share the same spacer and gaskets so I am sure it is not that. So I got disco ball working on that.

Will do more after the exhaust is done. Like paint the hood after this storm gets thru.
 

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74M35A2

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Don't run/drive it with the pinion spinning. Over-running clutch will seize, starter will spin 200,000rpm, and the commutator splays out like a peeled banana in a cartoon. Then the pinion gear breaks off and goes round and round inside the flywheel housing, milling the housing. Remove starter, I'll slam a new nose on it, then add more spacers or have a machine shop make up a thicker one of the difference needed. You can just do a depth measurement from starter mounting flange on housing to ring gear face. I'll try to cross-reference the stated p/n's of the original, but they may have been a unique deal. But thicker spacer and longer mount bolts could handle it, same/same.
 

simp5782

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Don't run/drive it with the pinion spinning. Over-running clutch will seize, starter will spin 200,000rpm, and the commutator splays out like a peeled banana in a cartoon. Then the pinion gear breaks off and goes round and round inside the flywheel housing, milling the housing. Remove starter, I'll slam a new nose on it, then add more spacers or have a machine shop make up a thicker one of the difference needed. You can just do a depth measurement from starter mounting flange on housing to ring gear face. I'll try to cross-reference the stated p/n's of the original, but they may have been a unique deal. But thicker spacer and longer mount bolts could handle it, same/same.

I don't think it is unique. the starters both are 20 inches overall. One just has the shorter cone. Ill see. Spacing it out can be a pain cause of the bottom bolt that has the smaller head so you can actually get it on. But I will know in the morning.
 
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