front wheel drive doesn't work

[sterlun]

I got stuck.... in nothing. Had the 818 in the woods behind the house to drag a big stump out of my way. Backed in, chained up, stuck. Never even pulled tension on the chain. Put it in low range and all it did was dig in. Obviously these trucks have open diffs. Only had left side spinning on both rear axles. I got out and looked while low range was spinning and the front wheels weren't doing anything.

After a friend graciously saved the day pulling me out with his 5 ton I saw that there was some grease slung out around the inside of the front right tire. Smells like gear oil but looks like it comes more from the CV boot. I don't think this would affect my front wheel drive though.

So I checked out the TM which isn't as 'all-knowing' as I had hoped. All it said was to check the air lines on top of the t-case for leaks or kinks. When I get time I will look at those but my truck doesn't lose air pressure and kinks seem unlikely to me in that situation, but I'm sure there's a way.

So I wonder if any of you guys know of some simple checks/procedures I could run through to try to narrow this down. I tried the search but admit that the search and I do NOT get along. Your help is appreciated.

 

[BKubu]

From this limited information, I'd say you have a bad sprag. The sprag itself can be replaced...or you can swap the entire transfer case. In certain rare circumstances, I've heard of sprags freeing up. I have never tried doing that. I've always either replaced the transfer case or replaced the sprag. Replacing the sprag is costly and a lot of labor...but so is replacing the transfer case. I'd bet the truck came from GL so you have no recourse. If you bought it from a private seller or a dealer, contact them to let them know that the truck is not a 6x6 as it was probably advertised.

 

[doghead]

Do you hear air shuttling when you shift 1st and reverse?

Have you ever lubed the air shuttle valve?

Has the front drive ever worked for you?

 

[KsM715]

When sitting in the truck with it running or atleast with the air tanks full, shift from first to reverse and back several times. Do you hear an air release when you shift from first to reverse? If not You may have the valve on top of the transmission plugged up.

 

[bevanet]

You should hear a release of air as you move the gear shift from a forward gear to reverse and from reverse to a forward gear. If you don't, you may have a problem with the sprag activater. If you hear the air, I would get it stuck again and very carefully look to see if the front drive line is turning. Then put it in reverse and see if it is turning in reverse. I would never crawl under it with wheels spinning, but you should be able to see the driveline from a safe location.

 

[KsM715]

Dang DH types faster than I do.

 

[sterlun]

OK so I don't like the suggestion of getting it stuck again.

Thanks a lot guys for all your quick responses. I'm running back and forth to the truck as you guys respond.

After I aired it up, shifting out of 1st into reverse I don't hear anything. When shifting OUT of reverse I get a good strong PSSHHT of air. I turned the truck off and went through the motions again. When going into first or into reverse I hear air that sounds like it's escaping but not a PSSHHT. Only get that when coming out of reverse.

 

[sterlun]

Oh, Doghead;

I have not lubed the air shuttle valve as I don't know what that is. That'll lead me back to the TM I'm sure. And this is the first time I've had it in a front wheel drive situation so I doubt if it has worked since I've had it.

And yes it was a GL purchase.

 

[m139h2otruck]

Jack up front end. With air tanks full & engine off, shift into reverse. You should not be able to rotate both front tires forward, but they will rotate in reverse. Shift into neutral or any forward gear and the reverse should be true. If either or both of these tests fail, the sprag or air system (valves, lines cylinder) that runs the sprag is bad/broken.

 

[jasonjc]

On a side note check that the front and rear tires are the SAME SIZE. Not just by the numbers on the tires but are indeed the same size. If not you could mess up the sprage if you have not all ready. And all the stuff above too.

 

[M813A1]

After you had gotten stuck and engaged the transfer had you tried to backed up ?? Sometime after the transfer is engaged you need to backup a bit to make sure it has engaged before going forward !! But it you did not hear a heavy clunck as you shifted from Reverse and into 1st gear then your air valve could be sticking !!

 

[73m819]

do you here air hiss after you shift into reverse, does it keep hissing, if so the shift cylinder on the transfer needs new seals, if you don't here a hiss and a clunk as you shift forward to reverse, the reverse shift air valve is bad, if you don't here a hiss and a klunk going from reverse to forward, your forward shift valve is bad and if you here the hiss but not the klunk, it is most likely it's the cylinder

 

[sterlun]

I did back up with it in low range several times. I was trying to find some solid ground. I never heard any heavy clunks and I don't get the surge of air release going into reverse, only coming out. I don't get any air release surges with 1st gear at all.

I searched the TM for "sprag" and "air shuttle valve" but those words are not in there. I'm gonna pull the cover from the floorboard maybe this evening or tomorrow and see if I can find something in those air lines. I really hope it's that minor. I need to get this truck sold so I can move on to a different one.

 

[sterlun]

Ron, with the truck aired up and turned off, when going into reverse it doesn't make any noise but once in it does keep hissing. When coming out of reverse it gives a loud hiss. Going into 1st no noise but once in 1st it continues hissing as well. No noise coming out of first.

 

[73m819]

sounds like you need to rebuild your transfer shift cylinder, it sounds like air is by-passing the seals in the cylinder, there are a few GOOD threads on this, one by FLORIDAIAN ( or close spelling)

 

[augiedoggy]

Hey there,
Mine gives a loud pshhhh from the air valves at the transmission when shifted into reverse or out of (meaning neutral or any forward gear). Basicly it either applies air pressure to one air hose OR the other going to the air actuator on the transfer case. The psshhh... is the air venting from the opposite side.
its of course common for the air hoses to leak. One or the other Always has pressure on it.
hope this helps i'm still learing too

 

[73m819]

Hey there,
Mine gives a loud pshhhh from the air valves at the transmission when shifted into reverse or out of (meaning neutral or any forward gear). Basicly it either applies air pressure to one air hose OR the other going to the air actuator on the transfer case. The psshhh... is the air venting from the opposite side.
its of course common for the air hoses to leak. One or the other Always has pressure on it.
hope this helps i'm still learing too

If thay are leaking, thay need to be fixed, the OP stated that the hiss is staying after shifting, about the only way this can happen, is if the air is leaking around the seals in the tcase shift cylinder

 

[sterlun]

Ron, would that be the cause of my front wheel drive not engaging?

 

[73m819]

YES, with the air bypassing, it wont push the piston

 

[augiedoggy]

If thay are leaking, thay need to be fixed, the OP stated that the hiss is staying after shifting, about the only way this can happen, is if the air is leaking around the seals in the tcase shift cylinder

I know you're right, I was just trying to pass on my tiny bit of knowledge I've accumulated recentlly..


Hey...and.....uuuuu..... my actuator cover bolts (4 long bolts) were a little loose allowing air to leak from the copper sealing washer.

Everybody on here is so knowledgable and helpful I just want to pitch in if can to return the favor!

ok thats all I got .......best of luck!