I've searched about 12 threads, and I've looked over Section 27 in the FSM...the only thing mentioned is the rear diff air pump is located "under the rear seat, passenger side."

Are they referring to the cargo cubby? That's what I assumed, as the FSM doesn't go into any more detail, and I can't find a picture anywhere. If so, there's nothing in there but a white rectangular female plug, which is not connected to anything. What's this plug for?!





...and where the heck is the rear diff air pump?! Help! Thanks in advance!

Ok, now I'm really bummed out.

I got out my hand pump and put the truck in 4Lo. Thankfully, this time the center diff locked (had issues with that earlier). I connected the pump and gauge to the hose where it meets the rear locker, and I pressed the R/D Lock switch...viola, exactly 5psi.

So then, I connected the hand pump directly to the air inlet at the diff, and pumped 5psi into it. I put everything in neutral, and jacked up the rear axle. With the rear diff pressurized @ 5psi, I spun one tire by hand - the other tire spun in the opposite direction. It doesn't leak...it seems to hold 5psi when pumped directly into the diff's hard line just fine. <img src="/forums/images/graemlins/confused.gif" alt="" />

I tried a couple more times, pressurizing and de-pressurizing the rear diff. I would feel a solid "thunk" while spinning the tire as it reached 4-5psi. When it was de-pressurized, the opposite tire almost freewheeled. When it "clunked" as if it locked, the tires were solidly connected, but again, when spun by hand they went the opposite direction.

Shouldn't they have spun in the SAME direction? Or is some resistance on one tire necessary?

Lastly, I removed the switch and (I think) checked for continuity. I connected each pin to my multimeter, switched it to 20 ohm, and moved the switch pin. When it was at rest, there was no continuity. When I moved the pin, the meter read 0.01-0.02. I assume the switch is good?

I don't think the rear was locking up earlier today, as I was sliding all over the place, and the rear diff light flashes. What do I troubleshoot next? Does my pumpkin need to come apart? Was it locking and I just didn't notice? I'm perplexed. <img src="/forums/images/graemlins/scared.gif" alt="" />

Oh, and lastly, where are the wires I would need to splice into to wire the switch directly to the pump? Photos would be nice if possible...I just need to know what needs to come apart, and what color wires to splice. This way I could have easily checked the locker in 2WD without taking anything apart. TIA! <img src="/forums/images/graemlins/ignore.gif" alt="" />

Went outside again to double-check. Again, here were the results:

Rear isn't locking up. Confirmed my suspicion today in the dirt. I was hoping it was just the rear detection switch, but it wasn't.

1) Connected hand pump's gauge to rear diff pump outlet (at the end of the hose that connects to the diff). Perfect 5psi coming from the pump.

2) Removed rear diff detection switch, checked with multimeter...checks out OK. (ps...why does it say I have to remove the differential to take this switch out? What does the end of the pin connect to? I was able to get it back in by rotating the rear tire a bit until it felt like it lined up and wasn't hitting anything...).

3) Applied 5psi via hand pump directly to rear diff inlet. Wheels feel like they "lock" more firmly together when the pressure is applied, but they still turn the *opposite* direction.

4) Lost 0.5psi in about 120 seconds of turning the wheels and watching the gauge...the needle moves slightly as I would turn the tire back and forth (lock to lock...it was in park), but it doesn't seem to be a leaker. The pump does not run very long (only a couple seconds), and I don't hear any air leaking out of the breather.

If it's not the actuator in the diff...what part could it be, mechanically, that it's taking in the proper amount of pressure but not locking up? The car runs and drives just fine, with no noise or slop from the rear end. I also changed the rear diff oil less than 2 weeks ago, and it was perfectly clean with no sign of any broken metal bits or shavings inside. I have to get this locker working for a trip coming up - I'll really be hurting without it! <img src="/forums/images/graemlins/scared.gif" alt="" />

I'm thinking about removing the diff cover tomorrow (and saving the synthetic I just put in it 500 miles ago...) so I can watch/listen as I pressurize it.

Anyone have any other ideas as far as further diagnosis?

I would have looked at it closer tonight, but I was too busy removing the passenger window regulator that broke last night, and finding a way to secure my window shut so I can lock my truck.

When it rains, it pours, eh? <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

I don't think you can remove the diff cover... as the 3rd member bolts into the diff housing. I'd try whacking on it with a hammer to see if you can jar the housing, and get the locker to fully engage. Sounds as if you have enough pressure and it's moving the actuator, but just not enough.

Eek! The thought of that scares me...should I use a rubber mallet or actually whack it with a steel hammer?! I'll try tapping on it tomorrow as it's dark outside now, and I'm all cleaned up.

What did you mean by 3rd member? There's red sealant all around the rear diff cover, so I figured it's been off at some point. I found this on YouBoob so this is what I'll be looking for on the inside...

http://www.youtube.com/watch?v=sRz2yqH-1AE

...was this someone on here?

IIRC that all comes out the front, and the rear "cover" is part of the housing. Just whack the crap out of the housing with a hammer while you actuate the locker. If you've got an assistant handy, have them spin the tires back and forth to try and jar those insides lose, and free up the mechanism.

Whatever you do, do NOT put any more than 6-7 psi on that locker. it WILL blow out the diaphragm.

Yea, I was following the FSM for the pressure, it's just a little hand pump.

So...OK...help me out here. I pull my truck out of the driveway to leave, and I hear something in the rear diff "rubbing" now.

I disengage 4WD and the lights all go off, indicating RWD. But I still heard the noise (sounds like maybe the pin of the diff lock detection switch is making contact with something), so I turned around.

As I turn around, I get "bark...bark...bark..." from the rear end, as if it's now locked up in 2WD. <img src="/forums/images/graemlins/confused.gif" alt="" />

Now I'm really confused. I only got about 4 houses down so hopefully I didn't destroy the detection switch. I guess now I see why the FSM says to remove the friggin' diff in order to remove the detection switch. <img src="/forums/images/graemlins/drunk.gif" alt="" />

Any ideas as to what might have happened? It wasn't locking up in my driveway...I pulled out the switch, put it back in...pressurized it with a hand pump then put it all back together...and all of a sudden, it's locked with no air pressure.

Ugh. <img src="/forums/images/graemlins/angry.gif" alt="" />

I would opt for a big-ass rubber or plastic mallet.....

Air/vacuum systems can be problems to diagnose as there are diaphragms and seals that can be damaged in testing.

As there is a switch that depends on physical position, does it have correct actuator movement?

As something is supposed to move within the diff, is it moving??