M817 Front axle no longer pulls - all of a sudden

[Construction]

My M817 front axle does not dependibly pull. It just started a couple of weeks ago. When it does pull, it pulls well. No odd noises, etc.

Any advice on what it could be? Is there any specific maintenance item I need to look at?

I have to put it in first and then reverse and then first, etc. to get it to engage. Most of the time it will, but sometimes not. It seems to be getting worse.

Any advice would be great.

C

 

[jcappeljr]

Sounds like the sprague.they do that alot.

 

[Construction]

What can I do?

 

[hoop]

Welding works.

 

[Construction]

Weld what?

 

[hoop]

Remove Jack shaft. Take front cone off the transfer case, remove the little sprag things and weld. Attach an air switch and you are either always in or always out of front drive.

 

[doghead]

Has anyone here done that(welded the sprag) ?

 

[73m819]

Not sure where you got your welding info
BECAUSE I Really don't think this will work because ,

First there are TWO sprag clutches F/R, if you weld you will lock up and break something because you WILL BE in F/R at the same time.

Second, a sprag is a OVER RUNNING clutch, only comes in when the rears are turning faster then the fronts in the xcase, if welded and NO slippage, the front and rears will be trying to turn at the same speed,THIS TYPE of clutch is NOT MADE to handle this and SOMETHING WILL break, just like running two different size tires on the front and rear of a 4x4 locked in 4x4 on the street,

The air shift on the xcase is just for shifting the sprag into F/R, NOT in or out, the 5t xcase is NOT LIKE the deuce air sfift with a JAW clutch, and both the front and rears are turning the same soeed in the xcase

 

[73m819]

First try oiling the xcase air shift cylinder (take the air lines loose and put some air tool oil in, then shift back and forth), sounds like it is sticking, look for air leaks, when shifted in forward, do you hear air, if so it is leaking past the packing/rings in the xcase air shift cylinder

 

[M813A1]

I agree with 73m819 look at the air shift valve and clean and lube it first before you do anything drastic as welding !!!! Besides it is alot easier then taking things apart and welding !!

 

[hoop]

I was just offering another way.
I think Squirt-Truck knows what I am talking about. Maybe he will chime in.
Maybe it only works in forward drive....I do not know at this point.
A local logger does this to his when the sprag quits working properly.
I will try to get some pics and more detail, if anyone wants it.

 

[asafk]

as far as I understand the sprag operation, the reason for haveing one for the reverse and one for the front, is because the speed difference (between front and rear t-case output shafts) is in the opposite direction when drivein in opposite directions.
so if everything is welded, (t-case front output shaft to the frond driveshaft) the front will be engaged all the time, front or reverse. no need for an air valve - nothing to engage anymore, it's engaged. permanently. much like driving a part time 4x4 in 4X4 all the time.
As long as we're not driving on good traction - it should work. if a truck never-ever drives on road - I see no problem with this.
am i wrong here?

Asaf.

 

[Construction]

I will try the air tool oil. But, it would be great if I could engage it or not when needed.

When the truck is loaded with sand or dirt, it is not a problem - it pulls great. It is when I am either empty or hauling my bull dozer or excavator behind on my tag trailer when it is the biggest problem. And it is only recently that it has been.

How often do all of you add air tool oil? Is this something I should be doing routinely? I have been running this truck for years and never had to do anything but change fluids and drive.

I do not hear any hissing in forward. But, in reverse it does "stick open" from time to time. I have to put it back into reverse and it stops.

Thanks,

C

 

[hoop]

I "think" not sure, the reason there is a forward and a reverse sprag, is so that the front will "free wheel", if being pushed of sliding, forward or backwards.
Less likely to Jack knife.

 

[pctrans]

Get a rebuild kit for the air diaphragm mounted on the x-case (2 rubber seals and 2 copper washers). Make sure you hone out the cylinder before installing the new seals.

 

[ODdave]

how common is it that the sprage or something internal breaks?

 

[73m819]

I "think" not sure, the reason there is a forward and a reverse sprag, is so that the front will "free wheel", if being pushed of sliding, forward or backwards.
Less likely to Jack knife.

I think you better find out HOW a over running clutch works, The 5t xcase IT IS made up of two OVER RUNNING CLUTCHES F/R, nothing to do with free wheeling or a "JACK KNIFE", The reason there is a forward over running clutch and a reverse over running clutch is because the SPRAG is set up to engage in ONE direction ONLY

 

[doghead]

A good start would be to Google "sprag clutch".

Then to be less generous with advise on topics that you are not quite "up on".

 

[73m819]

how common is it that the sprage or something internal breaks?

Not very common, most times it is a valve or cylinder issue, a few times the sprags may get gummed up and stick, just drain the case, put diesel in, run down the road without a load, drain, one or two times ought to clean up things

 

[hippiedude]

........... Listen to 73m819 ......................