Sprag STAYING engaged in reverse.

[johnknp1]

-M35A2 with sprag t-case

So I learned the hard way that rolling in the opposite direction of the gear your in will pop the sprag and possibly break it as I popped it after I bought my truck. I never drove the sprag style in the national guard, only the air shift and was ignorant of the difference. When this last big snow hit my truck would not engage in either direction. I got under and noticed that my reverse rod assembly was complete trash and couldn't even be adjusted per the TM. I ordered a new one, installed it, adjusted it per the manual and with one tire jacked up I could spin it freely in both directions in 1st gear and also in reverse, so no sprag engagement at all, no matter what I did with the adjustment. I resolved myself to buy an air shift t-case this summer and accepted that my truck would be rear wheel drive until then.

So today I drove to work and when I went to back into a parking space I went into 6x6 on flat dry pavement and left light rubber marks from the front tires to where I stopped. It felt like it was engaged good and strong and had not left any marks coming into the parking lot. There was no slippage of the rear to instigate an engagement and I had backed up a few times in town running errands without any engagement.

I really don't want to ruin my front axle, Im at work on a 13 hour shift and have to drive it home in the morning. My big concern is that it decides to go into 6x6 going forward as well. There's nothing in the TM to address this particular situation. My idea is to just remove the reverse rod assembly before I leave in the morning, that also might be a terrible idea. Also may be noteworthy info, it seemed a little stiffer going into first as I drove around today. This is the first time ive driven it since messing with the sprag or the reverse rod assembly.

I would really appreciate any input on this from someone with experience with this odd situation or knowledge on the sprag or anything that will stop me from messing up my truck. Thanks a million.

 

[gringeltaube]

....... My big concern is that it decides to go into 6x6 going forward as well...

Don't worry, that won't happen - certainly not without that shift rod installed.
And I would say it's not a "terrible" idea to remove it completely until you find some more time to play with the adjustment and get more familiar with its function. (this post might help...)

From what you described I firmly believe that it wasn't your reverse sprag clutch that suddenly revived and locked up, but rather the front sprag that for some reason remained engaged, even after the transmission was already fully shifted into reverse gear.
The rubber marks you noticed was your front axle pushing the rears, so to speak.

You just need to figure out when/why this situation can happen. Possibly the rod is adjusted too short. Also check the rubber mounts of the T-Case.


G.

 

[johnknp1]

It hit me like a bag of bricks, the best thing to do is to just remove the front drive shaft and throw it in the bed for now. I started thinking that if the reverse rod assy isn't there it might be free to engage either sprag as the wind blows, I will try to adjust it to center as best as I can, but I'm definitely dropping the drive shaft in the morning before I take off.

Correct me if I'm wrong, but the shaft into the T-case that is affected by the reverse rod assembly is in a neutral state normally, engages the front sprag when pulled away from the tcase and engages the reverse when pushed into the tcase. I might have that backwards on which way does what, but conceptually it would have to do something both ways or the adjustment procedures make no sense.

Enlightenment hurts my face.

 

[gringeltaube]

No, there is no NEUTRAL position; it is in FORWARD, by default! There is an internal coil spring that keeps the forward (sprag)clutch engaged, all the time, except when you shift the tranny into reverse.

I suggest reading that post I linked to.



G.

 

[johnknp1]

Your right. Reading that post clears it up, thanks for that. I planned on reading it but i didnt have much chance on the job. Good, descriptive info. Im going to try to adjust it properly before i go to removing the drive shaft. If my forward sprag is engaging that strongly is there a chance the sprag is still good and will work if i can pull my head out of my butt and get it adjusted properly? Also, how could it fail the tire spin test in the tm both fw and rv no matter how far i adjusted it either way but now engage? Seems like like it shouldnt be able to at all.