Center Diff Lock Issue

KingPrat

KingPrat

New member
Took my 4Runner "off-road" for the first time yesterday, and decided that I'd work the 4Lo/Center Diff a little to make sure everything was functioning properly. I can just about guarantee that this is the first time in 8 years that this had been done (other than 4Lo testing on test drive...)

Turned the dial for 4Lo, shifted right away, and drove through a couple muddy spots no problem.

Then hit the center diff lock switch - and I got a blinking light on the dash. So - I turned it off and on a few different times, and there's an electronic click from behind the dash, so I know the actual switch works. Drove slowly forward/backward to see if that would loosen something up, etc. Did all the tests trying to get it to lock it up.

No dice. :dammit:

So, after searching, I'm still unclear as to which actuator actually controls this function. I know that there's 2, one for the 4Lo/4Hi shift, and one for the center lock. I also know one is a $2500 repair, and one is a $250 repair.

So which actuator is the culprit here? Spoke to a service department close-by, and almost got an answer out of the guy, but he realized I had done a bit of homework. He clammed up and said to bring it in for ~$90/hr to diagnose.

Any help/advice would be appreciated. I'd like to be able to do this myself, but don't want to get into something that's over my pay grade.
 
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In my case, my center locks easier when I have a bit of speed. Find a nice, long stretch of road and hit the center diff lock button going a steady 25 mpg (in 4H) and see if that helps to engage it.

(Just don't take any turns on dry pavement with the center locked)
 
Ive had really good luck getting my CDL to engage quickly on the trail if I am in neutral and rolling slowly forward or backward.
 
KingPrat,

If it goes into low range that's big. That seems to come up more often than a sticky diff lock. I'll bet it will switch fine in regular driving. Just find a straight stretch of road and don't be afraid to play with the throttle. Once you've got it working well, it's very fast. Since you have the V8, exercising the diff lock is easy to do any time it occurs to you.
 
No need to be in nuetral. You can push the button anytime. Mine generally engages within 2 seconds. No need to stop or do anything just push the button when you feel it will need to be locked up or unlocked.
 
Only low range requires neutral (and stopped). If the diff lock actuator is in good working order, it's nearly instantaneous (especially after the first cycle) while driving straight at any speed.

Consequently, there's no reason not to exercise it often.
 
I just went out and experimented with this. I could lock the center diff in gear and moving in hi and low range without going to neutral. I was on my cement driveway when I tested low range so I could not get up to much speed but in went in and out smoothly. You need the wheels to be pointed straight so that the driveline does not get bound up.
 
Guys, this is all fantastic advice. I really appreciate it.

However, if you read through my first post, I'm curious as to which actuator controls this action, not tricks on how to get it to shift in.

I have tried forward, backward, sideways, fast, slow, etc. and it will not go in. Electrical click behind the dash tells me switch is working, but other than the blinking light on the dash, nothing else to tell me it's functioning beyond there.

So, is it the internal or external actuator that controls the actual locking of the center diff?
 
JB. said:
KingPrat,

Try this thread. Pics on page 2.

http://www.toyota-4runner.org/4th-gen-t4rs/80283-2004-v8-4x4-actuator-replacement.html

Also, people have reported some success with tapping on the actuator housing with a rubber mallet.
Click to expand...

Jeff S. said:
Center Diff Lock issue - Toyota 120 Platforms Forum
Click to expand...

Ouch. Perhaps a date with a rubber mallet is in order before proceeding any further. Hopefully I can get it to free up.

Doesn't seem like Guerilla is on here much anymore. Wish he had gone into more detail with a write-up.

:cheers:
 
So here's an interesting tid bit now that I looked over the diagrams... the transfer cases not physically different from each other, even the acutators are the same for the V6 (VF4AM) and V8 (VF4BM), but what is different is the components on the input shaft (V6 has extra syncros and such for 2Hi-4Hi) & the shift forks (the V6 utilizes a shift fork with two holes for BOTH shafts of the actuator while the V8 utilizes only one to "lock" lock the center differential.) Also, I am unclear how our center differentials are even considered differentials or even Torsen Style? The internals look just like a mini manual case...

View attachment CONPONENTS__40001_.pdf (VF4BM)
 

Attachments

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BlackWorksInc said:
So here's an interesting tid bit now that I looked over the diagrams... the transfer cases not physically different from each other, even the acutators are the same for the V6 (VF4AM) and V8 (VF4BM), but what is different is the components on the input shaft (V6 has extra syncros and such for 2Hi-4Hi) & the shift forks (the V6 utilizes a shift fork with two holes for BOTH shafts of the actuator while the V8 utilizes only one to "lock" lock the center differential.) Also, I am unclear how our center differentials are even considered differentials or even Torsen Style? The internals look just like a mini manual case...

View attachment 77693 (VF4BM)
Click to expand...

This helped me quite a bit actually. I was confused by the 120 post in that the way he described the dealer's diagnosis that the actuator was inside the TRANNY. I was under the impression that it was 2 separate actuators (I figured he meant transfer case, not tranny) one external, one internal.

I will keep this updated as I troubleshoot, hopefully giving the actuator and case housing a few love taps will free things up.
 
BlackWorksInc said:
Also, I am unclear how our center differentials are even considered differentials or even Torsen Style? The internals look just like a mini manual case...
Click to expand...

The differential appears to be a part of the rear output shaft sub assembly shown on pg's 3591/3623 and 3594/3626. The diagram on 3591/3623 shows how the gear selector forks from the actuator engage the outside of this sub assembly and then on pg 3594/3626 you can see that Toyota lists the core of this subassembly as the differential. I know one of the primary benefits of the Torsen Gen 3 differential is its small compact size but damn, its pretty well buried inside other components. Thanks Blackworks for posting those diagrams, really helpful!!
 
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Synister said:
The differential appears to be a part of the rear output shaft sub assembly shown on pg's 3591/3623 and 3594/3626. The diagram on 3591/3623 shows how the gear selector forks from the actuator engage the outside of this sub assembly and then on pg 3594/3626 you can see that Toyota lists the core of this subassembly as the differential. I know one of the primary benefits of the Torsen Gen 3 differential is its small compact size but damn, its pretty well buried inside other components. Thanks Blackworks for posting those diagrams, really helpful!!
Click to expand...

That's the thing though, it looks just like a gearset you'd find in a manual trans. This doesn't really look anything like a "Differential" let alone a "Torsen Style" one. How does it "sense" and "adjust" for torque? Maybe I'm just tired and missing something, but that's what bugs me about it.
 
BlackWorksInc said:
That's the thing though, it looks just like a gearset you'd find in a manual trans. This doesn't really look anything like a "Differential" let alone a "Torsen Style" one. How does it "sense" and "adjust" for torque? Maybe I'm just tired and missing something, but that's what bugs me about it.
Click to expand...

Question asked, question answered, although I think this may be a T-2 diff, ours is a T-3 and could be a little more compact or just slightly different internally. This is from a FJ site as well so the clutch plates may or may not be present; to my knowledge the T-3 does not use clutch plates. The key take away here is that it appears Toyota has actually machined the housing of the diff to be the different gear sets for 4HI unlocked / locked rather than attach a separate ring gear like most differentials. Saves space, weight, etc. More good reading here http://www.torsen.com/products/T-3.htm

torsen2.jpg
 
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Stupid question.. Is this the center lock button? I've only had my Runner for almost a month now and I wasn't quite sure what this button does.

u6e8a9u6.jpg
 
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