RTH: Rear Locker Actuator

BirfMark · 11-01-09, 12:46 PM

This past snow storm, my rear locker wouldn't engage - the light on the dash just stayed flashing.

With the help of some older posts, I was able to remove & start trouble-shooting my rear locker actuator. It runs in & out nice & smooth, but it seems as though the actuator rod that connects the actuator assembly to the shift fork isn't in the correct position - it needs to move out one tooth or so.

When I retract the actuator rod all the way using the 9 volt battery method, and try to reinstall the assembly in the axle, the hole for the shift fork doesn't line up. Same goes for if I extend the actuator rod & try lining up the bolt that goes from the shift fork to the actuator rod (while the axle is locked, of course).

How do I realign the actuator rod with the shift fork hole? Do I need to take the actuator motor and spring assembly apart in order to adjust this, or can I just run the shaft out a little with the 9 volt & reinstall everything?

This is the thread that makes me think I can just 'adjust' the actuator rod position with the 9v: http://forum.ih8mud.com/80-series-te...volt-test.html

But this image from the FSM makes me think I have to take everything apart to realign the gears or something:
Image refused to prevent confusion.

BirfMark · 11-02-09, 09:05 AM

UPDATE: Seems to be fixed.

I measured at the axle to determine where the bolt hole in the actuator rod needed to be relative to the mounting face of the actuator assembly (not the round section I'm measuring in the photos above - measured from the flat face where the orange sealant is). The numbers I came up with were:

Locker Unlocked (actuator rod retracted): 1.2"
Locker Locked (actuator rod extended): 1.6"

When I pulled the actuator assembly, when I measured the shift rod in the unlocked position, I was at 0.9", so it needed to be extended by 0.3".

All I did was remove the three 10mm bolts holding the gear cover on, and removed the cover. Thankfully, when I removed the cover, I found this:

A nice & clean, unrusted gear and spring assembly. Phew. Note the orientation of the gears & springs - the is the how everything was aligned before I moved on to the next step.

Inside was the gear assembly, which I was able to carefully pry up and remove with a small screwdriver. I used the edge of the actuator housing as a fulcrum, and pried under the gold colored plate seen in the above picture. It didn't take much force, and it popped out. There are no clips or retainers holding the main gear & spring assembly in - it is simply sandwiched between the actuator housing & the gear cover plate. This is what the reverse side of the main gear looks like:

You can see where the contacts have been wiping across it.

And with the gear & spring assembly removed, this is what the interior of the actuator housing looks like:

At this point, I simply pulled the actuator rod out until I reached the magic 1.2" number (measured from the main, flat face of the assembly, to the center of the bolt hole in the shaft). I then reinstalled the gear assembly into the housing, and checked for continuity between pins 4&5. If there is continuity between 4&5, that means that the actuator is in the unlocked position, and the motor will not continue to run. Raventai's post here: http://forum.ih8mud.com/80-series-te...tml#post172256 was invaluable for this information. I had to remove & rotate the gear assembly one tooth at a time until I had the actuator rod in the correct position and had continuity between 4&5. I think I only ended up clocking it two, maybe three teeth in order to achieve the correct alignments on everything.

After that, it was merely a matter of reinstalling the gear cover plate, and reinstalling the actuator assembly into the truck. I took it for a quick test drive last night in a gravel lot, and the locker engaged in about two seconds while driving a tight turn.

Hopefully these pictures will help someone else down the line.

corsair23 · 11-02-09, 11:19 AM

Great info!

Thanks

Tools R Us · 11-02-09, 11:55 AM

Some notes:

The above FSM page is for the front locker, a different setup.

On the rear actuator, running with a battery connected to the motor only confirms that the motor runs. Doing this can get you into trouble, as you found out the limit switches determine where the motor stops, so when running the motor directly it's easy to go too far, messing up the timing. The timing is the relationship between where the limit switches stop the motor and how far the shift shaft is extended.

I never run the rears directly with battery power, only plug it into the harness, have a helper turn the switch, run it in and out confirming the measurements before installation.

Be sure to seal it well when assembling, I use RTV/silicone sealer on the cover and motor housing. Don't want it to leak and rust out.