Is my M813 sprag sticking?

[comike27]

I have 1982 m813 usmc model with rear lockers . I think my sprag is stuck engaged because I can't get up to speed and the truck shutters when put into third gear like its towing a trailer . I'm planning on dropping the front drive shaft and seeing if the problem goes away . If truck goes better I'm going to flush out the transfer case with diesel then next would trouble shoot air poppets . If the sprag is stuck does it do any harm if the front drive shaft is removed . What's the procedure for flushing transfer case put in diesel run and repeat thanks . Mike

 

[comike27]

also am I supposed to hear a air valve noise when shifting from reverse to first I havent tried with the truck off but when running I can't hear any air valve noise .

 

[Ajax MD]

Yes on the air sound. I'm new, and can't answer your other questions about flushing.

 

[simp5782]

Just fill with diesel. Drive it for a bit drain and refill. You should hear the air psht sound when shifting. Even with the engine running

 

[comike27]

If the sprag is stuck and I drop the front drive shaft will that no longer hurt anything . Thanks the info guys

 

[162tcat]

I have 1982 m813 usmc model with rear lockers . I think my sprag is stuck engaged because I can't get up to speed and the truck shutters when put into third gear like its towing a trailer . I'm planning on dropping the front drive shaft and seeing if the problem goes away . If truck goes better I'm going to flush out the transfer case with diesel then next would trouble shoot air poppets . If the sprag is stuck does it do any harm if the front drive shaft is removed . What's the procedure for flushing transfer case put in diesel run and repeat thanks . Mike

Have you checked the trans, transfer, diffs and hubs to see if anything is excessively hot? Same issue in high and low range? Might have a bad bearing somewhere. Could also have a brake sticking. I would check all of those items. Dropping the front driveshaft would be a good start to trouble shooting.




Sent from my iPhone using Tapatalk

 

[comike27]

I haven't checked for heat that's a good idea will do that tomorrow, the truck rolls freely so wasnt thinking of anything stuck definitely something to look into .

 

[comike27]

I haven't tried to see if the problem is the same in low range yet that was also planned for tomorrow .

 

[Floridianson]

Did you roll backwards in a forward gear with the clutch in or roll forward in reverse with the clutch in? Did you hop the rears playing in the mud? Sounds like you locked up the sprag and I don't believe a diesel flush is going to help plus problem not in the poppets. You can PM me for my phone number and I will tell you how I fixed my locked up sprag but I got lucky.

 

[comike27]

I haven’t rolled in the opposite direction in gear , this truck has sat since 2002 I’ve only owned 6 weeks I haven’t driven it much yet .

 

[Ajax MD]

I haven’t rolled in the opposite direction in gear , this truck has sat since 2002 I’ve only owned 6 weeks I haven’t driven it much yet .

Ah, you're in the same situation as I am. (New (old) truck with deferred maintenance.) YOU have not rolled it in the opposite direction in gear, but SOMEONE may have, in its lifetime.
In any case, these guys will set you right. I'll be following because I have the same truck, minus the lockers.

An IR heatgun is your friend: https://www.amazon.com/Etekcity-Las...r=8-1-spons&keywords=ir+temperature+gun&psc=1
Safer and more accurate than using your hand.

 

[tobyS]

The sprag unit comes apart without taking the TC case out, I seem to recall. But first, I would take the cylinder apart and make sure the plunger is moving free. That air sound is changing from forward to reverse. Some people say the sprag has a neutral position in the middle, but I don't recall that, I only recall a forward position and reverse position. I've since sold my 817 so can't go look, but I recall only one air line going to the sprag shifting cylinder. I think there is a return spring and air is applied when reversing. That all has to work freely. Please check and see if one or two air lines go to the air cylinder and set me straight.

 

[comike27]

I’m going to check it out some more this afternoon I’m hoping if I remove the front drive shaft it will drive normal then I’m going to troubleshoot from there. I could only get the truck up to 40 mph downhill flooring it, it was a long slow ride to get diesel mostly 30 mph .

 

[Ajax MD]

I’m going to check it out some more this afternoon I’m hoping if I remove the front drive shaft it will drive normal then I’m going to troubleshoot from there. I could only get the truck up to 40 mph downhill flooring it, it was a long slow ride to get diesel mostly 30 mph .

Although the absence of air sounds during shifting from R to 1 indicate at least some kind of problem, how do you figure that you had some kind of drag rather than just a loss of engine power?

I apologize for asking this, but are you certain that you had the transfer case selected for the high range? 30mph is the top speed for the low range, and that seems to be where your speed topped out. (The transfer case lever should be pulled UP rather than down to the floor.)

 

[Floridianson]

The sprag unit comes apart without taking the TC case out, I seem to recall. But first, I would take the cylinder apart and make sure the plunger is moving free. That air sound is changing from forward to reverse. Some people say the sprag has a neutral position in the middle, but I don't recall that, I only recall a forward position and reverse position. I've since sold my 817 so can't go look, but I recall only one air line going to the sprag shifting cylinder. I think there is a return spring and air is applied when reversing. That all has to work freely. Please check and see if one or two air lines go to the air cylinder and set me straight.

The other air line is on the transfer case and the Deuce has the return spring on the air shift transfer case so just one line.
Yes the is a position where there is no engagement without full air pressure.


As for the drag yes if you lock up the sprag it will feel like something is dragging and it is.
I am waiting for a call from him now.

 

[Ajax MD]

Flor- You'd better not just disappear after you purge your fleet. It would be a huge loss of knowledge.

 

[Floridianson]

Just talked to Mike and he is going to pull the air cylinder. Guess if the air cylinder had enough crud/rust it could stay in gaged the little bit it takes to be in gaged. The pics show how little it needs to be for in gaged. The piston can be in forward position or reverse but if the spring is not compressed with air it is not in gaged so a neutral.

 

[Floridianson]

Flor- You'd better not just disappear after you purge your fleet. It would be a huge loss of knowledge.

No most everything can be Googled or if not it is just smoke and mirrors. If you can't dazzle them with brilliance baffle them with bullsmit.

 

[98G]

I’m going to check it out some more this afternoon I’m hoping if I remove the front drive shaft it will drive normal then I’m going to troubleshoot from there. I could only get the truck up to 40 mph downhill flooring it, it was a long slow ride to get diesel mostly 30 mph .

Forgive me for asking the obvious.... but you're aware of the atypical shift pattern on these trucks right? You *are* in 5th gear?

 

[162tcat]

Could be bad diesel too. It's the thing sat since 2002 and you're still trying to run that old diesel the engine may idle OK but will be really low on power. Lots of things to look at, time to start narrowing it down.


Sent from my iPhone using Tapatalk