M813 transfer case issues

[timgc78]

Hello gentlemen I finally got my m813 running. I attempted to drive it but can't seem to get the transfer case to shift into hi or low. The transmission goes in all gears and I can see the short shaft turning between the transmission and transfer case. I have some air leaking at the poppets on the transmission. Could air supply to the transfer case be the issue?

 

[simp5782]

No.

If the linkage is not moving at the transfer case for high to low then you will need to crawl under and look at it. Maybe use a prybar against the linkage for motivation in or out to lock it all the way in. It may be adjuster wrong

 

[tobyS]

Hello gentlemen I finally got my m813 running. I attempted to drive it but can't seem to get the transfer case to shift into hi or low. The transmission goes in all gears and I can see the short shaft turning between the transmission and transfer case. I have some air leaking at the poppets on the transmission. Could air supply to the transfer case be the issue?

The sprag clutch uses air to shift forward to reverse. It could be in a bind if it is not shifting...possibly....

You should research the tranny. Tthe sprag is a one way clutch that releases the gears from a difference in gear ratio back 16/1 and front 17/1 or something like that. Can you jack it up where a wheel could turn and relieve the drivetrain stress?

 

[timgc78]

No.

If the linkage is not moving at the transfer case for high to low then you will need to crawl under and look at it. Maybe use a prybar against the linkage for motivation in or out to lock it all the way in. It may be adjuster wrong

 

[timgc78]

The linkage is moving freely. The shift plunger is moving slightly and I did already attempt to use a pry bar to give a little persuasion both forward and rearward. It just doesn't seem to want to go into gear in low or high. I've already made sure there wasnt a bind on the drive train.

 

[Lovetofix]

Was the transfer case shifting normally last time it was driven?
Your transfer case is stuck in neutral, some of these have a very strong detent on the shift fork rod. It could also be the gears are not aligned to let you engage either high or low, usually you can get into one or the other to get you rolling a bit then you can grab the range you want.
If you can, roll the truck slightly forward or backward as you try and engage the transfer case. Sitting still my M817 will go into low much more easily than high range.


Sent from my iPhone using Tapatalk

 

[timgc78]

Was the transfer case shifting normally last time it was driven?
Your transfer case is stuck in neutral, some of these have a very strong detent on the shift fork rod. It could also be the gears are not aligned to let you engage either high or low, usually you can get into one or the other to get you rolling a bit then you can grab the range you want.
If you can, roll the truck slightly forward or backward as you try and engage the transfer case. Sitting still my M817 will go into low much more easily than high range.


Sent from my iPhone using Tapatalk

 

[timgc78]

I bought the truck not running and had it towed home. I've since installed all new wheel cylinders and the engine seems to run good so far. The drive shafts were completely taken loose and wired up for transport...both front and rear axles. Which tells me there may have been a drive train issue that parked the truck. I reassembled and tried to get it to move and the transfer case isnt wanting to move from neutral. When I bolted the drive shafts back up the transfer case spun both front and rear yokes together freely.

 

[Lovetofix]

A slightly different issue that will not affect getting the transfer into gear but still could be an issue. You said the front and rear yokes were turning together, was that with the truck running/aired up? With zero air pressure the front yoke should turn independently of the rear. With the sprague engaged front propeller shaft, the front axle shift ring is held in the neutral position by springs and needs air pressure to put into either forward or reverse position controlled by those poppets on the transmission you said were leaking.
This is a totally separate control system from the high/neutral/low of the main transfer case and I wouldn’t worry about it yet but it needs to be assessed at some point before you take it on the road. I can outline an easy way to test the sprague by jacking up one front wheel but some other time. You need to get the transfer case in gear first any way you look at it.


Sent from my iPhone using Tapatalk

 

[Lovetofix]

There is a square cover on the transfer case, high on the passenger side. Taking out those four bolts and removing the cover will give you a good look at the shift fork and gear and may shed some light on it all.
Also, I have had several Rockwell’s apart for rebuild so I am not sure if the shift detent spring and ball is under that square cover or under a bolt cap next to the cover but you could try removing that spring and ball temporarily to get rid of that interference on the shift rod. It can be a lot to over come if it is rusted or things are not well lubricated.


Sent from my iPhone using Tapatalk

 

[timgc78]

A slightly different issue that will not affect getting the transfer into gear but still could be an issue. You said the front and rear yokes were turning together, was that with the truck running/aired up? With zero air pressure the front yoke should turn independently of the rear. With the sprague engaged front propeller shaft, the front axle shift ring is held in the neutral position by springs and needs air pressure to put into either forward or reverse position controlled by those poppets on the transmission you said were leaking.
This is a totally separate control system from the high/neutral/low of the main transfer case and I wouldn’t worry about it yet but it needs to be assessed at some point before you take it on the road. I can outline an easy way to test the sprague by jacking up one front wheel but some other time. You need to get the transfer case in gear first any way you look at it.


Sent from my iPhone using Tapatalk

 

[timgc78]

Yes the front and rear yokes turned together with no air. That's why I said there was no drivetrain pressure on the transfer case.
You mentioned a 4 bolt cover. I looked the transfer over rather well today. The front cover looks to make up the entire front of the case. The rear half of the case has cast reinforcing ribs all the way around and unless I over looked the access plate.... I didn't see one. I was concentrated on getting the shifter to make a choice.

 

[Lovetofix]

The access cover is on the side, not the front or back. It is next to the truck frame up high on the passenger side.


Sent from my iPhone using Tapatalk

 

[tobyS]

my first impression was the sprag engaging for the wrong direction.

My 817 is long gone but I had the tc apart and don't recall an access plate.

 

[timgc78]

The access cover is on the side, not the front or back. It is next to the truck frame up high on the passenger side.


Sent from my iPhone using Tapatalk

 

[timgc78]

I've looked over the tm now and I see the access plate and the detent bolt beside it. I'm curious how much I'm gonna be able see with the transfer in the truck. There isnt much room above the mount. I may hafta drop it to get it to free up or fix it.

 

[Ajax MD]

I've found the transfer case to be a bit grumpy to shift, especially if left sitting for long periods.

Squirt some "liquid persuader" on the shift plunger, move the truck forward or backwards a few feet and try again. I know you said the plunger moves but it sounds to me like you're not getting nearly enough travel in either direction.

Also, if the lever is hitting the floor or seat, you have a lot of slop or you're out of adjustment. If the shift linkage is worn, you might need a trip to the hardware store to fabricate some linkage shims/spacers to eliminate some of the slop.

You could also drain the oil and check for metal bits and then replace it with fresh oil. Be sure to use only GL-1 mineral based oil as called out in the lube order. These older trucks have some "yellow metal" in the transmission and maybe the transfer case (I can't recall right now). The modern GL-4 lubricants are not compatible with these softer metals.

 

[jasonjc]

Disconnecting the drive shafts is a standard tow procedure , so don't read to much into that. Also under that cover plate is a big set screw that holds the shift fork to the shaft. If it is lose it will not move the shift fork.

 

[timgc78]

 

[timgc78]

View attachment 817607

Well guys turns out it wouldn't shift because the input shaft is is broken clean off. The forward gear on the input is totally stripped of teeth. The transfer seems to be locked in 6 wheel drive. Anybody seen this before?