Why do I have no front drive in forward, but do in reverse?

[dma251]

My XM813A1 is doing great EXCEPT for the recent snows lately have made it very obvious that when in forward gears I have no forward axle engagement but in reverse I do.

I have a spare complete transfercase, but I'd rather get some possiible ideas lined up before I tear into it. I want to do this quick and easy before the next snowfall.


I will add that when shifting from forward gears to reverse I can hear the air "psssttt" sound, and there are no weird noises or clunks from the truck.

I've also got an opportunity to buy a set of locking front hubs for it, any idea what they are worth?

 

[Recovry4x4]

RE: Why do I have no front drive in forward, but do in rever

Someone else will chime in on the adjustment of the air stuff for the solenoids. Buy the hubs even though they aren't much value with the sprag case. 5 ton hubs are few and far between. I haven't seen any since the 80's and they were made by Warn.

 

[rizzo]

Re: RE: Why do I have no front drive in forward, but do in r

Someone else will chime in on the adjustment of the air stuff for the solenoids. Buy the hubs even though they aren't much value with the sprag case. 5 ton hubs are few and far between. I haven't seen any since the 80's and they were made by Warn.

if a person drove it alot they would be good for a rear axle.

the noise you hear is the air venting when you switch from forward to reverse. the first think I would do is remove your air lines that hook to the t-case and make sure you are getting air out of both lines. one in forward and one in reverse. make sure the flow is good too.

 

[G744]

RE: Re: RE: Why do I have no front drive in forward, but do

The air piston cylinder on the transfer can rust up, causing it not to move freely and stop the signal getting to the sprag fork. It is a simple operation to pull the can and clean it out.

As stated, front axle hubs are not useful on a 5-ton with the sprag t-case.



dg

 

[dma251]

RE: Re: RE: Why do I have no front drive in forward, but do

Sorry to hear that about the hubs.. They sure are cool looking. HUGE monsters!

I may put them on anyway just for the neat factor. What do you all think they are worth?

 

[M1075]

RE: Re: RE: Why do I have no front drive in forward, but do

DMA-

Do you have a picture of these hubs? I'd like to see what you are talking about. I didn't know there was such a thing for 5 tons!

 

[Recovry4x4]

RE: Re: RE: Why do I have no front drive in forward, but do

They would be good for a 900 seriers truck or even Leonard Jones Baby HEMTT. M1075, seen them quite a bit in the early days of monster trucks and them using 5 ton running gear.

 

[dma251]

RE: Re: RE: Why do I have no front drive in forward, but do

I don't have a pic now, but as soon as I pic them up I'll post one. We are fabricating the center spline shaft for them. Should be done soon, it's a pretty easy deal.

 

[m139h2otruck]

See my post about the sprag unit in our M139. Your's may just be gummed up or as suggested, the air cylinder is rough. Check that you are getting full air pressure to the cylinder in both forward and reverse, ours was leaking at the shift valves, bad.

I still maintain that if a valve was installed in the air system, closing off pressure to the shift valves, then the sprag goes to neutral and a set of front hubs would be worthwhile. Want to let me know where your source is?
Thanks

 

[dma251]

Sure, I'm getting them from the guy I bought my truck from. He's a MV collector, mostly focusing on armor. He found them at a swapmeet a few years ago and just stashed them away for a rainy day.

He suggested welding the sprags and using an air-actuation setup to engage the front axle. Anyone done that?

 

[Junkyard Wars Crusher]

I still maintain that if a valve was installed in the air system, closing off pressure to the shift valves, then the sprag goes to neutral and a set of front hubs would be worthwhile.

M139' , I agree. I have done this, and it does work as described.

http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=6944

 

[rmgill]

Not engaging the Front axle is how M819 got his 5 Ton stuck on our trail ride.... There's definately a method to disable the front axle.

 

[dma251]

I like this airvalve idea. Tell me more.

Which airline does the valve go on? Is that all? Do I need to do anything to the sprags? (I still need to figure out why there is no reverse engagement)

 

[Junkyard Wars Crusher]

I like this airvalve idea. Tell me more.
Which airline does the valve go on? Is that all? Do I need to do anything to the sprags? (I still need to figure out why there is no reverse engagement)

Ok, I am no expert on this, I am just trying to explain what I did to my truck. If anyone can refute this, please do - I would like to learn also. Let me also add that my truck is the G744 (M39) series - I am not sure if this is applicable to your 800 series.

dma, I sent a PM with my phone number, if you want to talk this through

 

[dma251]

So where is the advantage to running locking front hubs with this setup? Seems like aside froma little bit of drag from turning the front diff/driveline, it accomplishes the same thing.
Like I said before, I'll still probably put the lockling hubs on, just cuz they're so darn cool looking.... But I definitely think this air valve method is the smart way to go with these trucks.

Would a M35 Deuce front axle engage lever work for this? Is it vented?

 

[dma251]

Oh, by the way, Junkyard Wars Crusher- thanks a lot for the help. It really made it clear for me.

 

[jwaller]

there is actually a MWO from the military that does this exact thing. it simply cuts the supply from getting to the transmission. it's the same switch that the airshift deuces have.

RON's M819 has this mod on his truck and it was there when he got it from the gooberment. the only thing I don't like about it is that is seems like if you don't ever use it and leave the air off 99.9% of the time the system would quickly become inop when you needed it.

probably won't stop me from doing it to my truck but at least it wont leak air anymore.

I don't see what it's going to help bc the entire front driveline will still be turning unless you find some locking hubs built by warn 30yrs ago.