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This weekend I had my 78 710m "significantly" offroad for the first time at Uwharrie National Forest. Extreme rocks, mud, bumps, etc.

Although everything ran fine, I needed to engage my rear locker once and the lever would not budge -- nor would the front for that matter. This came after a period of heavy brake use, engaged 4wd for about 45 minutes, and reduction gear. In other words, the terrain exceeded my skill. (for now!)

When I got home and cleaned everything off, the lockers would now engage and the lamps would illuminate. I took a very small drive around the neighborhood and confirm the lockers were on, because of the impossibly heavy steering and clattering. No, I didn't drive more than about short distance with them on.

Now the problem.... when I tried to disengage them, the levers went up fine but the lamps stayed on and the diffs were still locked. After crawling back home (struggling of course to turn) the front lamp disengaged, then the rear one. Lockers were confirmed to be off, and everything was normal. This took probably 2-minutes from the time I released the levers.

1) What would have caused the diffs to be impossible to engage while on trail? I hate to sound like a newby, but does the system share hydraulic fluid with the brakes? If so, could a mushy brake and likely air in the lines explain it?

2) Once engaged (back home), why wouldn't they disengage? Same situation? Was the "wait time" really just a question of rebuilding pressure in the lines and brake?

Confused in NC.


Obligatory picture attached. Mine is the one with Andre's bumper and winch.

Over time, and especially without use, the fluid in the lines can become waxy, cheez-wiz like. That's probably why they wouldn't engage. After a while, with pressure on them from when you attempted to move the levers it probably helped break a clog free in the lines which is why you were able to engage them later on. They can be slow to dis-engage for a few reasons but in your case was probably due again to the fluid consistency.

No, the brakes and the lockers are separate systems but both use DOT3 brake fluid.

The reservoir for the lockers is behind the panel with the locker indicator lights. I would start by using a turkey baster or similar to suck out as much of the fluid in the reservoir as you can. If the reservoir is really nasty it would be best to remove it and give it a good cleaning. Then fill with clean brake fluid and flush the system by bleeding each of the 3 locker slave cylinders until clear fluid comes out. Keep filling the reservoir as you go.

This should solve your problem. It has for me in similar times.

Edit: Forgot to add - don't force the levers. They will break and are pricey.

Sometimes my rear lockers stick engaged, so I just vary the RPM or come to a complete stop; if that doesn't work, putting it in reverse always disengages them almost immediately. At times my levers get stiff, but I've learned how to forcefully finesse them down and I don't have a problem, but I imagine they would break if you just forced them. I'll vouch for the nastiness that builds in the lines; when I flushed my system, all sorts of chunky stuff came out. I know I didn't come close to answering your questions, but hopefully it helps some.

CentAr,

Two different causes of lockers staying engaged. One is binding within the drivetrain. When you engage a locker, it locks two "gears" from turning independently. In the case of the differentials, it's keeping both left and right wheels spinning at the same speed. When you go around a corner, the inside tire travels less distance than the outside tire, thus the need for a differential. When you go around a corner with the differential locked, it puts pressure on the locked parts. Off-road, the tires simply skid a little bit. On-road, pressure builds on gears or splined shafts. So when you try to unlock, the binding locking collars don't want to release. Often, backing up will release this pressure and allow things to unlock. Having this problem off-road probably points to gunk in the lines. This situation could be worse if you also have a sludge problem like pcolette described.

I also think JRR has sludge in the lines causing resistance both to locking and unlocking. The problem with moving the locker lever down would not be caused by binding in the drivetrain.

Paul,
You mean: don't force the levers!

I have also had similar problems and have bled the system. The big thing seems to be regular use. I joined a hunt club this year and I have to go six miles down a really awful road before I even get to the gate at the club. I found that I am using the lockers more down to the gate than once I have arrived. The first couple trip the lockers were stiff and slow to disengage. But now that the trips are at least once a week they are working perfectly.

So, my advice is to use them often to keep things free.

This is not what many of you think it is.
It's a battery bulb syringe with the nozzle bent with the help of a heat gun to go through the blank gauge port
to fill/suck out the hydraulic fluid reservoir behind the dash. Has worked for me quite well.

So, my advice is to use them often to keep things free.

I was told by Andre and Jim L. that every time I take the pinz out, flip the lockers ( I do it on straight a-ways, lower speed and one lever at at time) to keep the hydraulic fluid moving to prevent the waxing problem. However, if they now stick that bad, I would
flush the system first!