sprag gear transfercase question

[jeep thing]

i have a 816 wrecker,i beleive the transfercase in the truck is a sprag gear case,its the one where the front axel locks in on its own when it feels like it,which is only about half the time that it should lock in,my question is can i take the two air lines coming off the top of trans and run lines up behind the dash and put in a switch like the deuce has to engage the front axel,has anybody done this ,does this sound like a good idea or bad ideathanks any help would be appreciatted

 

[KsM715]

Dang wheres that popcorn smiley? I'd also like to know if thats possible.

 

[jwaller]

sure it's possible but it will only fix a problem in the valve on the transmission. if you have a problem with the transfer case then no it won't fix the problem.

 

[m16ty]

There was a thread about this same thing a couple of days ago. It's my understanding that all the air valve does is switch the sprag from foward to reverse depending on the trans gear. It doesn't engage the front end. If you added a manual valve you'd more than likely tear up your t-case even more.

 

[jasonjc]

 

[KsM715]

http://www.steelsoldiers.com/5-ton-larger/41467-m816-sprag.html

Jeep Thing,
He tried to answer here but couldnt, I linked it just incase you missed it

 

[m139h2otruck]

All the 5 tons (M39s and M800s) use a sprag transfer case that has air shift through the transmission valves forward and reverse. Some outfits added an air switch like the M35s that just shuts off the air to the transmission valves, so then the sprags go into neutral. DO NOT run the truck if the air is hooked up but not correctly shifting between forward and reverse.

 

[jeep thing]

thankyou for the info,next question is there a direct bolt in for 816 wrecker that is not sprag case so i can control when the front axel engages,and if there is another choice is it weaker or stronger or the same,any advantages or dissadvantages

 

[m16ty]

Well you could put in a deuce case but it would be weaker. I've seen some big civilain trucks that were all wheel drive. May find something there that would work.

 

[jwaller]

thankyou for the info,next question is there a direct bolt in for 816 wrecker that is not sprag case so i can control when the front axel engages,and if there is another choice is it weaker or stronger or the same,any advantages or dissadvantages

no. not unless you have bill gates money and if you did you wouldn't have bought an old rusty army truck.

fix what you have and it will work wonderfully and probably cheaper than anything else you can dream up.

 

[m16ty]

no. not unless you have bill gates money and if you did you wouldn't have bought an old rusty army truck.

I've said this before, If won the lottery I'd still have junk. It would be higher quality junk though .

 

[papabear]

I agree with the fix what ya got theory.

We have 6 5tons in the CAMO group...all with sprague units and they all work. It's actually a pretty good system.

I do agree it might be better to switch the front axle when ya think ya might need it but heck..as long as she knows when to do it...let her roll!!

 

[Csm Davis]

the sprags only work in 1st and reverse if they get air pressure from the switches on the transmission so you can put switch in the main line to the trans to turn off the front shaft completely. I am thinking of away to engage the foward sprag in the higher gears without damaging it.

 

[jasonjc]

NO

The sprag works or should work in all grears. It only shifts into fwd in frist but it stays fwd unless you go into reverse.

 

[Csm Davis]

Maybe CSMS is wrong they only worked on them for last 20+ years but it makes sense to me because when you pull it out of first you hear it release the only other gear you hear it on is reverse I tell you what as soon as I can I will unhook the line and see for myself if the guys that have been fixing them for the army know what they are talking about.and jasonjc this not a smack down I realy will find out. Because I need to know if they are fixing the trucks right.

 

[dk8019]

I suppose the Sprag could be setup to work in all forward gears by just adjust the mechanism that decides when and where air goes, I don't think manual switches would be required. I would think a manual switch, say one for forward, and one for reverse, could result in very bad things happening the one time you didn't pay attention.

 

[jasonjc]

So the army made a truck that can only drive down a muddy road in 1st grear?

 

[Csm Davis]

So the army made a truck that can only drive down a muddy road in 1st grear?

that's what I said when they told me!

 

[Westech]

so does anyone know the TM number or a link to it... I have a 813 here for a SS member at Gl and the valve is leaking

 

[martinsaunders06]

the sprags only work in 1st and reverse if they get air pressure from the switches on the transmission so you can put switch in the main line to the trans to turn off the front shaft completely. I am thinking of away to engage the foward sprag in the higher gears without damaging it.

this is wrong.The sprag will operate in reverse and as soon as you pull back into neutral and then consequently any forward gear it then changes back again= its not a forward or 1st gear thats selects it ,its the neutral position, hence if you sit in neutral and stationary your sprag is engaged in the forward position and this is why you should not roll backwards in neutral or any forward gear except having reverse gear selected as this is why it twists up the transmission and will break something.I fitted a m35 type dash air switch into the air supply to the gearbox valves and it works great, transfer sprag is in neutral and been fine for 2 years now. martin