M923A2 CTIS Problem

[Andyrv6av8r]

Is there a source for parts on the Eaton pcu? I have 2 dead coils. Part number on the coil looks to be 5C-411-P7.

I have new coils. PM me if you're interested.

 

[1 Patriot-of-many]

Just replace the coils. It's not that hard.

 

[KN6KXR]

I recently got around to making the tool I needed to test wheel seals per the TM each wheel. It's not totally necessary to plug the QRV off but be advised the QRV will not close until you take the tool off so with the assembly under 80psi pressure you need a firm grip or accidents will happen. Tool works great.

Actually I should say "tools". One has a JIC (aka AN) end and the other an SAE. The JIC is in front and the SAE is in the rear I know not why. It's just an adapter, a tee, a gauge and a tank valve. That's it. Best thing I've done after rigging 120psi shop air to drop to the truck. Identified bad hub seals in a heartbeat. Even with the truck off it was hard to hear EXACTLY where. The damn drums are so big....

In my case it immediately identified the three right side hubs as failed and the left rearmost as slow leak. FML it's going to be awhile until my CTIS is fixed!

Way better than testing one thing at a time then letting it freak out, flatten all the tires and spend oodles of time refiling them. Highly recommend.

 

[KN6KXR]

Well I fixed the right two rear hub seals. There was shredded rubber fluffy crap in there. I assume the seal. I changed all the fittings over to JIC. This required 4 new 3/4" 45 degree NPT/JIC adapters and tube ends. The tube ends were expensive but at least they are longer, have more grip and are a better product. Now everything on the truck is JIC and I'll continue the theme as I work on the vehicle to standardize. At some point the brake system will need love and I think I'll go with DOT brass or stainless push lock on the air supply. This ain't going to be cheap but is going to be right. Way it is at least I'm cheap labor!

Some useful notes:
-I still have to do a front hub seal but am impatient so picked up a JIC cap to blank it off. It's super easy to reach this and cap it.
-With one hub blanked the system sees an imbalance and will initiate the run flat mode (see manual). It may fault but a reset and it'll keep going. When it gets close to pressure the run flat mode will disappear and it'll act normally. It does this more at lower pressures like X-C than HWY. It's also sensitive to having the truck compressor running at full speed than idle. Times out I think. I expect this to get better when all 6 wheels are connected.
-CTIS works fine (once proper pressure achieved) when rolling and one wheel blanked. I tested this for about 30 miles. It does it's checks, releases air, etc.. All good. I'm adding to my on board spares a JIC cap, some service wrenches and my test tool. That way if I have a failure in the field I can blank off just the one and be about my business until I can make a repair.
-The truck is new to me and I'm still getting to all the fluids. Not a lot came out of the axles when I did the seals. After the seals I topped up the axles and they took about a gallon apiece (which is a bout a third of their capacity). Luckily the gears look great (thanks US ARMY for over engineering these!). I think low axle levels may be a contributor to CTIS hub seals going bad. The seals need that splash lube on the outsides to keep intact. Also I cleaned the hub passages front to back there are annular passages that allow the lube to travel from the flange side to the interior and lubricate the inner bearing and therefore CTIS seal. Mine had grease chunks in there I assume from the RSMS monkeys and it may have impeded flow.

That's about it. Front seal on order. Super happy to have an operational CTIS system! Thought I would update this as somebody may find the info useful.

 

[Stellaevil]

Well I fixed the right two rear hub seals. There was shredded rubber fluffy crap in there. I assume the seal. I changed all the fittings over to JIC. This required 4 new 3/4" 45 degree NPT/JIC adapters and tube ends. The tube ends were expensive but at least they are longer, have more grip and are a better product. Now everything on the truck is JIC and I'll continue the theme as I work on the vehicle to standardize. At some point the brake system will need love and I think I'll go with DOT brass or stainless push lock on the air supply. This ain't going to be cheap but is going to be right. Way it is at least I'm cheap labor!

Some useful notes:
-I still have to do a front hub seal but am impatient so picked up a JIC cap to blank it off. It's super easy to reach this and cap it.
-With one hub blanked the system sees an imbalance and will initiate the run flat mode (see manual). It may fault but a reset and it'll keep going. When it gets close to pressure the run flat mode will disappear and it'll act normally. It does this more at lower pressures like X-C than HWY. It's also sensitive to having the truck compressor running at full speed than idle. Times out I think. I expect this to get better when all 6 wheels are connected.
-CTIS works fine (once proper pressure achieved) when rolling and one wheel blanked. I tested this for about 30 miles. It does it's checks, releases air, etc.. All good. I'm adding to my on board spares a JIC cap, some service wrenches and my test tool. That way if I have a failure in the field I can blank off just the one and be about my business until I can make a repair.
-The truck is new to me and I'm still getting to all the fluids. Not a lot came out of the axles when I did the seals. After the seals I topped up the axles and they took about a gallon apiece (which is a bout a third of their capacity). Luckily the gears look great (thanks US ARMY for over engineering these!). I think low axle levels may be a contributor to CTIS hub seals going bad. The seals need that splash lube on the outsides to keep intact. Also I cleaned the hub passages front to back there are annular passages that allow the lube to travel from the flange side to the interior and lubricate the inner bearing and therefore CTIS seal. Mine had grease chunks in there I assume from the RSMS monkeys and it may have impeded flow.

That's about it. Front seal on order. Super happy to have an operational CTIS system! Thought I would update this as somebody may find the info useful.

Great to hear, we hope to have some better wheel valve parts coming soon that will solve the old cold temperature issues.

 

[KN6KXR]

Great to hear, we hope to have some better wheel valve parts coming soon that will solve the old cold temperature issues.

From what I understand talking to some motor pool guys that were stationed in AK the issue was moisture in the lines (for the most part) causing their malfunctions. Occurs to me that, on the truck I have at least, the air supply is right off the wet tank and there's a rather whimpy moisture separator under the dash. Maybe an investment there is a good idea? Mine leaked and I stuck a schraeder in there and periodically bleed it. I live in a temperate climate though so for me it's not worth chasing......

I did get my whole system working. For just a minute. Then the CTIS ECU went dead. I walked the pins in the harness from the schematic the truck is fine the ECU just won't do anything. So I got some older green replacements and the CTIS works. Unfortunately I can't seem to locate a 676603 at all which I think is the updated one. One I had was a black box 676422 which was a 70/80psi but at least had comms. I don't know if the green boxes had comm chips. So anyways I'll keep looking for either of those as Spicer says they have J1708 and J1939 available. According to the schematic not pinned to the harness STE/ICE I'd have to make an adapter (that would be too convenient!). I saw your post about the adapter cable I may take a stab at making one. Looking at a STE/ICE kit on eBay not because it'll do much for me on a wrecker but because it appears the cheapest way to get a Dearborn adapter!

Well anyways as you can tell I'm over in the deep end and on the steep section of the learning curve. I see some folks have had luck with talking to the CTIS on other platforms but not much on the M939A2. We shall see if I get someplace or go mad and give up on the way. I dunno I'm pretty stubborn.....

 

[KN6KXR]

Somebody sent me a PM request for a picture of my test tool I carry and I can't add to a PM so posting the image here. Basically it's a gas pressure test setup from Home Cheapo with a different gauge then plumbed to a JIC fitting. So if I have a suspect wheel I unplug the flex line from the supply under the truck, swing it down, connect this and test. The cap on there can then blank off the bad wheel. Zip tie up the flex line and now at least 5/6 of the system functions as it should. Beats the heck out of filling all 6 tires because one wheel failed.

When testing it should hold 80 psi with no leak down. Be aware that the official Army tool has a valve to quickly release the pressure (close the QRV). With this when you unscrew it then it'll leak and then pop off with some force so you have to have a good grip on it and be ready for that.

When you have a bad seal you'll know it. Works like a charm. I've used it on the road once definitely recommended spare for those who travel with operational CTIS.