5 ton sprag stuck?

[jdgreen]

I have a 813A1 that seems to have the sprag stuck. It seems to be full time 6x6 and feels like i have detroit in the front of the truck. But im sure its the sprag is acting up, but not sure where to diagnose the issue and fix it.

When i put the truck in reverse gear, you can hear air blowing out of the hose on one of the sprag air hoses. Put it back in forward gear and it stops. (It leaks out so bad that i loose ALL air pressure even with truck running.)

When shifting forward to reverse or vise versa you do not get the "swoosh" sound like my other 5 ton. So i know there is a air issue. Just cant seem to find it. I have pulled the airvalves off the trans today and took them apart. Everything seems to be ok and good shape. It is the first i have took one apart, but it all looks good.

Do you guys think it can be the sprag itself? Other things to test it first?

Does anyone have the TM that shows the break down of the parts. All i got is a -10.

Also does anyone have the MWO explaining the air disconnect also for them?

Thanks

 

[73m819]

your xcase air piston is in need of a rebuild,
one more thing, are your tires the same in size , front and back

 

[jdgreen]

Yes. Stock NDT right now.

 

[73m819]

I;m guessing that the sprag is shifted into forward, but cant be shifted out to reverse because the xcase cylinder is leaking so bad, so what you are feeling is the windup from traveling in reverse while the sprag is in forward, try removing the air supply line from the trans valves, plug the line, this SHOULD allow the xcase to drop into neutral, you will NOT have front wheel drive till you do the fix and put air back the the xcase shift system

after doing this, jack up a front tire, be carefull, the tire may spin when it leaves the ground, it will be undoing the windup

 

[jdgreen]

It blows the air out no matter if you move or not. Just shift into reverse and it starts. I got the air pop valves off now and got to put them back on. I will jack it up tomorrow and spin it to see what it does. I plan on putting a valve in it to stop the airflow as i have seen wrote about being a MWO on here. I also want to get the Tcase working properly before it goes back out of my shop. I plan on doing a complete go threw on the trucks drivetrain once i get this tcase issue solved before i start driving the truck down the road.

I thought i read someone done a rebuild on the airvalve while in the truck. Been doing a search but can not seem to find it.

 

[73m819]

I think it was FLORIDAIAN

 

[jdgreen]

Well i got chance to supply air to the truck and jack one front tire up over last couple days. Tire did not have no wind up or tension on it.
If the shifter was in neutral the tire would spin freely forward and reverse.
If the shifter was in first or another forward gear the tire would spin freely forward and reverse.
If the shifter was in reverse the tire would NOT spin forward but would spin in reverse by hand.

I then took the driveshaft out and pulled my sprag piston cover off the front of the T-case. after i took the cover off i noticed that there was 2 orings on the outside of the piston. One had a chunck of the oring missing. Im hoping this is the issue? I took my hand and could easily push the piston in and it would pop back out via the resistance of the spring behind the ring collar. Do you guys think i need to tear it down rest of way or just take and replace the orings on the outside of the piston collar and put it back together and try it?


I also tried to take and swap lines and it still dont same thing when i done that before i tore it down. Just to check and see if lines was backwards.

 

[73m819]

rebuild it, your this far, why not

 

[Floridianson]

Sorry I did not catch the thread sooner. You don't have to pull the drive shaft or the flange. You just take off the nut holding on the piston and pull off cyl. as one peice. Replace it as one to as it is a little troublesome to put the piston back in the cyl. You have to use a small tool and get the first seal lip to run into the cyl. the second seal will go right in as it will be faceing the outher way. You should also do the seal on the transfer case that is behind the washer that is in the pic. I used a drill bit just a little larger than the peen hole that secures it in. Then just repeen it back. Memphis eq. had the rebuild kit in stock.

 

[jdgreen]

How much is memphis kit? Did it come with just seals or everything? I got the sleave off. But as stated might as well go threw and rebuild it.

Here is a pic of how it sits right now. Will take it rest of way down tomorrow.

 

[Floridianson]

The kit has everything you need. The piston seals are a PITA to put on but you can work them with a small non sharp tool if they flip on you. Yes I think I would remove the piston and do the seal I showed behind the washer.
Use good rubber lube. I get mine from a pool supply house so it is safe for rubber O rings.
I did not have to drill very much just a light touch and only had to touch two of the peen marks and the washer came off.
Make shure that seal is seated well and not deformed. I used a small blunt flat screw driver to seat it.

Also my piston seemed to like to be unscrew from the shaft. So counterclock twist to get it off and then screw it back on. You just have to snug it up on reassembely then replace the waher and nut and tighten down.

Sorry I don't rember price but was not much

 

[shootiniron]

Can someone please explain what the process would be to install a valve in the air supply to simulate the MWO that has been mentioned here.I would like to free myself of the "wind up worry".Also where would I source the valve?Thanks!!

 

[73m819]

It is just putting a air switch (valve)in the air SUPPLY line to the valves at the trans, this cuts and dumps the air to the valves, thus putting the xcase sprag in neutral, the deucs air shift xcase air switch works great

The air switch (valve) has to cut the air to the valves and also DUMP the air pressure that's in the line, other wise one side of the sprag will still engage for a bit till pressure is drawn off

 

[shootiniron]

Thanks!Got an extra deuce air switch?

 

[jdgreen]

I finally got time today to finish taking it off and reseal it today. I also had to screw it on and off to get the piston off. I also replaced the little oring behind the washer. Memphis got me everything i would need and they was decent priced. I also got enough to do another one so i do not have to worry about shipping if i ever have this same issue again.

Got it all back together and i hear the "swish" now and no air blowing out when in reverse. You can hear the piston moving. I did notice that if the truck is in Neutral or forward with air pressure you can not roll the front tire. If it is in reverse it will let the tire spin in reverse but not forward. But if you bleed all the air pressure off it will allow the tire to free wheel both directions no issues. Now just time to see if it all works out ok.