Disconnecting the fording kit on a M923...

[TacticalDoc]

Then I disconnected every line (and left it open) going to the 4 way intersection except the short line just above the motor. And, that still didn't help.

So its getting air from somewhere. I just don't know where it's getting pressure from.

I looked up and posted on those threads already in the past. And, checked the TM. That's why I'm doing what I'm doing but its not working. So, this problem seems specific to my vehicle.

If anyone, has answers please email me instead.

 

[Tow4]

Did you drain the fluid yet?

I posted a couple of Allison manuals. One of them explains how to check the fluid level.

You need to verify how much fluid is in there. Since you say it blows out when its running, you probably haven't checked the level. If you drain the fluid out, and put it back in, you will know how much is in there.

While you have the fluid in the bucket, look and see if there's any coolant in it. If the transmission oil cooler leaks it will make the transmission fluid level high also.

Report back after you have drained and refilled it.

 

[Jeepsinker]

The vent line on the transmission is plugged. Dirt dobbers do this all the time. Transmissions will build internal pressure all on their own with no pressure input and puke out of the dipstick if the vent is plugged. No two ways about it, that is your problem.

 

[TacticalDoc]

Did you drain the fluid yet?

I posted a couple of Allison manuals. One of them explains how to check the fluid level.

You need to verify how much fluid is in there. Since you say it blows out when its running, you probably haven't checked the level. If you drain the fluid out, and put it back in, you will know how much is in there.

While you have the fluid in the bucket, look and see if there's any coolant in it. If the transmission oil cooler leaks it will make the transmission fluid level high also.

Report back after you have drained and refilled it.

I did that and completely drained it. I didn't flush the lines. And it still did it. I also put it in all the gears before checking the level. It doesn't look like any other fluid is mixing. But the fluid looks like the torque converter is foaming the fluid as someone suggested to me. The other problem is that the vent could be blocked.

I thinking I need to tow it to a truck shop and change out the oil to the proper ATF. I don't want to mess around with it any more and damage anything.

Will need a tow...recommendations in Polk Co area?

 

[TacticalDoc]

Up date...

So, I took it to an Allison trans shop and they said its not the trans. The pressure build up is in the transfer case that is over flowing into the trans for some reason because the vents are connected. They said they can disconnect the vent from the trans and that should solve the problem but I wont be able to switch it between low or high gear. As a trans shop they said they don't work on the transfer case. I'm also going to have them flush the oil out and put in what they recommended which was Dex3. They said there will be less swelling of the plates with dex 3.

 

[RAYZER]

Low to Hi gear on the transmission or transfer case?

 

[TacticalDoc]

Low to Hi gear on the transmission or transfer case?

transfer case

 

[plode]

transfer case

That doesn't even make sense. A vent line on the transmission will have nothing to do with transfer case operation...
The transfer case has its own shift lever. The transfer case has an air interlock that keeps it from shifting from high to low without the transmission being in neutral, or by depressing the button on the transfer case shift lever. I disconnected that air line on my truck because it would not shift whenever the truck was up to pressure(~120psi), regardless of what I did with the button(which did function, but it still would not shift) or transmission selector. Now it shifts great, and still has plenty of resistance from shifting accidentally(what the air interlock was for).

 

[TacticalDoc]

what they told me is that the vent lines are connected between the t case and trans. If they disconnect it it wont over pressurize the trans but I cant switch the t case . I'll check back with them on Monday to clarify

 

[Jeepsinker]

They are bull*hitting you. Did they even look under the truck? The vents would have to be connected together with NO outlet for what they said to be correct.

 

[Csm Davis]

Okay just unhook the vent line on the transmission. Leave the other lines alone you are going to have so many things undone and twisted around you won't ever be able to get it back right. Don't go running other ball valves and lines. Deal with 1 problem at a time. First you are changing to many things at once, stop. Start with the transmission vent, unhook it. Crank the truck and check for fluid output on the vent then the dipstick as you make sure your level is correct. Do not change the type fluid yet. You have to narrow down your problems first. If you still have fluid pushing out the dipstick you have a problem with the vent it should be open to let pressure out it should have a little outflow but not enough to tell in 5 seconds of viewing. Once you have the transmission fluid problem fixed then move to the vent if you do have air coming from the transfer case check and make sure that all the air lines that got to it are in the correct place, the boys in green get in a hurry sometimes. See if the vent on the TC has air going out of the case or air coming from a line to the vent. Once you figure this out you should be able to drive the truck home or to a shop to have the fording kit checked and reattached. Come on doc if you are one this is like chasing down a bleeder, you can do this.

 

[TacticalDoc]

Okay just unhook the vent line on the transmission. Leave the other lines alone you are going to have so many things undone and twisted around you won't ever be able to get it back right. Don't go running other ball valves and lines. Deal with 1 problem at a time. First you are changing to many things at once, stop. Start with the transmission vent, unhook it. Crank the truck and check for fluid output on the vent then the dipstick as you make sure your level is correct. Do not change the type fluid yet. You have to narrow down your problems first. If you still have fluid pushing out the dipstick you have a problem with the vent it should be open to let pressure out it should have a little outflow but not enough to tell in 5 seconds of viewing. Once you have the transmission fluid problem fixed then move to the vent if you do have air coming from the transfer case check and make sure that all the air lines that got to it are in the correct place, the boys in green get in a hurry sometimes. See if the vent on the TC has air going out of the case or air coming from a line to the vent. Once you figure this out you should be able to drive the truck home or to a shop to have the fording kit checked and reattached. Come on doc if you are one this is like chasing down a bleeder, you can do this.

After disconnecting the fording kit I put it back together in the original way it was. So, that's back to normal. I didn't do anything to the trans because I don't know anything about the trans and t case. I'm not a mechanic. I dropped it of to Trans Diesel in Lakeland that is an Allison Certified shop.

 

[Tow4]

They are bull*hitting you. Did they even look under the truck? The vents would have to be connected together with NO outlet for what they said to be correct.

How do we know they are NOT connected together?

 

[Csm Davis]

After disconnecting the fording kit I put it back together in the original way it was. So, that's back to normal. I didn't do anything to the trans because I don't know anything about the trans and t case. I'm not a mechanic. I dropped it of to Trans Diesel in Lakeland that is an Allison Certified shop.

Are you a Doctor? If so you are probably a lot more of a mechanic than you give yourself credit for airlines are just like veins. And bones move like steel parts, if you can work on human beings you can work on trucks. Trucks don't fuss if you break something it just cost a little bit more money. I am willing to bet the guys at that shop have no clue about your truck, if they did they wouldn't be shy about the TC. I have been a mechanic all my life and would pull my truck out of a shop that was skiddesh about this simple of a truck.

 

[TacticalDoc]

I was able to get my truck looked at over the past 2 weeks. Summary...the trans was over pressurizing and oil was spitting/pouring out the trans fill tube. I disconnected the fording kit and it still did it. The problem was with the air shift transfer case diaphragm which was leaking and over pressurizing the transfer case. The transfer case vent is shared with the trans vent. This then pressurized the trans causing the motor oil to spit out of the fill tube of the trans. However, no t-case fluid spilled into the trans. This connection was disconnected which prevented the problem. Now, I need the diaphragm to be fixed in the t-case. You would think a certified Allison trans shop would be able to work on the t-case but not in this case. So, now its at a truck shop.

When it was at the trans shop I had the oil flushed and Dex3 added like they recommended. It shifts much better but feels like it has less power. When down shifting it doesn't make a big clunking sound and jerking motion especially when it shifts down into first gear. A big difference is noted.

I just wanted to update everyone in case this ever happens to anyone. It may be just on trucks with fording kits that share vents between the t-case and trans. I'm not sure if all trucks share this line or not. Or, if its just on trucks with fording kits.

 

[162tcat]

The air shift diaphragm shouldn't have any air pressure unless your in 6wd. Is it pressurized all of the time? If so, it's hooked up wrong and that's an easy fix. Now if it's also blowing air by the seal on the actuator and pressurizing the case, pull the actuator because the piston or seal is installed backwards. Also an easy fix.

 

[TacticalDoc]

It was not in 6 wheel drive and did it. I have it at the shop and the mechanic is looking at it.

 

[162tcat]

The piston could be installed backwards and the airlines installed wrong causing it to be pressurized but still not in 6wd.