Dif locks not working??

[Brentbba]

I know I don't really use the center or front and rear dif locks, but have attempted to at least 'excercise' them after what I've learned here to keep them in good working order.

Campground this weekend had nothing but dirt/gravel roads so spent some time before leaving Sunday morning to 'excercise' them. Shifted into Low (in both park and neutral)and Center Dif lock would not engage. Tried driving forward and backward a little to see if it would, but after a half dozen attempts, gave up. It would Not engage.

Drove home and for yucks I tried one more time in the driveway before resigning myself to posting problem here first and then giving my friendly Yota dealer a call. Center dif locked up on first try! Proceeded to then try to lock up rears and fronts, and both locked up immediately. Whew! What could have been going on? Cold engine/tranny first thing, or just lack of use initially? Don't know why they would not lock first thing and then after a 270 mile trip lock right up. Wondered all the way home if something had been fawked up when the pinion seal and bolt had been replaced a couple of months ago? Apparently not at this point. Opinions?

 

[TX_TLC]

Here was my expirence...

I was trying to exercise them in my drive way...and my CDL wouldn't engage...so I did the whole bit about the plug and everything...never getting it to work I added this to the list to be tackled...

Fast forward to a muddy road few weeks ago...I sink the back end of my truck in mud almost to the axle/center of the wheel. After spinning the tires in D and R...I think, "What the hell" shift into N, and pull it into 4low...again, no ABS or CDL light...but I leave it and press the accl. to see what happens...and BINGO, ABS and CDL lights come on...and it has worked like it is supposed to since!

Cross that back off the to-do list...

 

[mabrodis]

I've seen atleast one case of the lock sensor for the CDL not registering it was locked. What would happen is the CDL actuator would do it's job, engage the gear, but the sensor was bad, showing it wasn't locked, therefore the computer won't let you lock the rear or front.

To fix it they (I was working on other stuff) pulled out the sensor, used carb and brake cleaner on it, pushed it in alot (it's a bulb type one), worked it good and kept testing it with a ohm meter, it should read shorted when pushed it, after a few minutes of doing that it worked perfect. Put it all back in, poof, everything worked great. I've heard others have a similar sensor problem on the diffs (same exact sensor I think), and they remove it and clean it, etc.

Good Luck..

 

[Brentbba]

Location of sensor? Is it under the rig? I heard some clicking from underneath the steering column the first couple of times like something was trying to happen but wasn't.

 

[mabrodis]

The actual CDL sensor is on the front cone of the transfercase, not trivial to get to, but not impossible, it has a connector on it, and then it unscrews like a bit bolt, takes a big socket, like 1" IIRC. In this picture you can see some other sensors too, LowRange sensor, etc. (ok nevermind, in that picture you can't, but they are there, further back on the t/c)

Here is a picture of where it is:

Also here are the two fullsize pictures that show it and the wiring harness:
http://www.fzj80.com/temppics/tc_1.gif
http://www.fzj80.com/temppics/tc_2.gif

 

[Brentbba]

Thx - you have the FSM on CD or something? Pics look very familiar. hehehe

 

[mabrodis]

I have the FSM, but these pics were from a online subscription to http://www.alldatadiy.com which is a 'ok' place, useful when you can just grab pictures and throw them online but not always useful to actually find real procedures.

Good Luck,
Mark Brodis

 

[hoser]

Can the CDL Motor Actuator be accessed from the inside cab, once you remove all the plastic trimming?

 

[mabrodis]

I don't believe so, the only holes in the floor are for the actual shifters (tranny and t/c), but those aren't large and I doubt it's where you need to be. You could always try, the worst you could do is take all the interior apart for no reason, not the end of the world...

 

[IdahoDoug]

I just handled this exact symptom of no CDL/ABS lights by pulling that switch and cleaning it with brake cleaner and cycling, etc. Takes perhaps 5 minutes to have it on the work bench. Don't lose the gasket/washer which may stick to the housing - which is fine also. Mine now work on command after slowly going intermittent after years of little use. Note to self: Go wheeling more.

DougM

 

[Brentbba]

Doug - I've put her into low several times since getting home Sunday - never a problem. Lack of use I guess.

 

[Klunky Chris]

I'll add my knowledge to the collective.
I had the same intermittant problem described. It drove me NUTZ because you CAN'T lock the front/rear diffs if the center isn't locked!

I was worried the actual locking mechanism was goin bad... means tearing the X-fer case apart!!

If you test it (loose gravel is best, and make very tight turns in a circle) you can determine if it's working, just not indicating. When in the locking process, you will hear a *click* or *thunk* from just under the shift levers on the tranny tunnel. Aslo the tires will very noticably scrub in the gravel. You should be able to tell a big difference in steering wheel effort in turns.

Anyway: Mine was working fine, but my CDL and ABS lights weren't working. I cleaned the switch as described by others, but it was still intermittant. For some reason, (Murphy's law...) the darn lights would only NOT work when I was on the trail somewhere and needed it (read GSMTR)

I replaced it with a new one and flawless operation since. A bit expensive, (I think $65) but worth it... especially if you have F/R lockers!

HTH!

BTW: here is what it looks like

 

[Gumby]

My center diff wasn't working at all at the Cliffs Sunday. I had the rear manually locked, but no fronts. Didn't get stuck all day. I was blaming the tires until I got on the rockpile and could see that I was only spinning one front.

I can tell you for sure an unlocked 80 will outwheel a stock Heep every day of the week.

If it is a 4lo position sensor, will the Pin 7 mod cure it? I do have a center lock switch, but it didn't do anything. I have not done the Pin 7 mod yet, although I have had it in my hand before. I just could decide to just cut it, or wire a switch to it.

I'm sure I'll pull the actuator at some point, but probably after I wash it.

 

[Rich]

Gumby, the only effect that removing pin 7 from the connector on the diff lock relay box has is to prevent the center diff from automatically locking when the transfer case is shifted into low range. Not a cure for the problem you are having.

 

[Gumby]

Thanks, Rich.
My thought was if the ECM needs to see 4lo engaged to allow the center diff to lock, then maybe the Pin 7 and the CDL switch would allow it to lock even though it does not see 4lo from the position sensor.
I was hoping I could do an easy fix while the truck is still a muddy mess.

 

[Gumby]

Pulled the center diff lock actuator today. The top bolt is a bastid without dropping the crossmember and lowering the trans a bit. The contacts on the big gear were dirty, just like the rear, except nowhere near as bad. Cleaned 'em up and it locks right up again.