Diff Lock Question

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Aug 17, 2005
Forest Falls, CA
Tell me how this makes any sense...

I get the truck back from the guy in Portland and test the lockers. He said he was embarrassed to say, but he never engaged them or even used them once.

So i press the center diff lock button (have that the 7 pin mod) and i get no light on the dash, no abs light either (i can hear the relay in the kick panel). I figure, crap that's weird. So i try the diff locks anyways, like if the bulbs are out or whatever. The diff locks engage, good to go.

Yesterday for the heck of it, i try locking front and rear diffs without depressing the Center Diff lock button and they lock! How could that happen when the lockers need a green light from the center diff first?

So here's the quick overview of what i have..

-locking diffs without engaging CDL
-no ABS light
-no Center Diff Light

strange eh?
If you're hearing the click as you've found out, you are engagad. Had a similar problem years ago (before I used lockers!). Basically the center diff actuator either needs TLC (slee's site has instructions) or you can purchase a new one from Dan. I did the later.

Best way to test this theory on the center diff actuator is to unplug it an stick that most expensive of diagnostic tools available...a paper clip on the TRUCK side of the conntector and repeat your process. If the lights appear on your dash, the center diff actuator is shot or in need of repair.
Ok the center diff is locking with or without paper clip.

Paper clip in - i get no abs light or center diff light still. However, when in park i get a A/T P light. Which in the manual it says "Shift Four Wheel Drive control out of "N".


Im locked, but i just don't know what happened to my 2 idiot lights. They worked fine when i sold the rig :(
So you're seeing lights now with AND without the paperclip in the truck side of the connector? That makes no sense.
Negative. Im still not seeing ABS and Diff Locked with the paper clip IN or OUT.

I am however seeing that A/T P light come on with the paper clip IN when i put it in park. Without the paper clip i do not see this A/T P light.
If you're seeing the necessary idiot lights with the paper clip in, it sounds like the center actuator has gone bad. That tells me the electrical system in the truck is ok.
Yea, it is. No clue. You've run thru all the tests Cdan walked me thru diagnosing my center diff lock actuator failure. At the time I didn't have the center diff lock switch.

I also have not done the 7 pin mod. Can't see the need to lock fronts and rears in high. If I understand that mod, that is it's intended purpose. Center diff lock button alone allows the truck to lock the center in high and the 7 pin mod takes that a step further with the ability to lock the front and rear in high with the switch 'on', correct?
Plenty of benefits.

7pin/Center diff button is good if you want to limp home or off the trail in front wheel drive. Or if you want to be in true 4 wheel drive in snow/sand in high range. Or want to lock the diffs for sand/snow in high range also. They're great mods.
So, w/o the 7 pin mod, when I depress the switch, I'm in 4 high with the center locked only right? Good enough for me. For what I do, I just can't see the need to lock up fronts or rears in high.
Are you sure the center diff is truly locked, or just that you can lock the F/R diffs when you wouldn't normally be able to?

Have you driven on pavement when you are under the impression that the center is locked? If it truly is locked, you'll know because you'll experience the front and rear tires "fighting" themselves (like a normal 4WD vehicle would on the pavement in 4WD)

It sounds like the axle diff lock CPU is receiving the locked signal even though the center diff isn't really locked.

Do you have a multimeter (and know how to use it)?

Brent, another one of the biggest advantages of the pin 7 mod is that you can run in 4 low without always having the center diff locked. This is nice when driving on big rock formations such as encountered in Moab or the Rubicon, or...
The center diff is locked because i feel the drive train bind bigtime when i depress the CDL button on the dash.

And that's on pavement even with the diffs unlocked.

Im heading out for a trip, so i will diagnose this a little more when we get back.
Let me know when you get back; we may be able to walk through it with a meter and my EWD (unless you have the EWD for your rig)
Well, i guess the cruiser just needed to run some rough trail for a while. This past weekend we ran a trail with a ton of rocks, creek crossing and a few good climbs. I had to lock up the diffs a few times. Well, up and down the trail 2 times and on came my center diff light and abs light. Started flickering.. then all of sudden stayed on. I locked up and unlocked the rig probably 20 times this trip and now the dash lights are back to normal.

I guess she just wanted to do some harder trails or something other than a fire road :D



(i didn't get any shots of the rough stuff, i was too busy trying to make it up with the trailer in tow)
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Good news Dave! She just wanted some exercise!

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