Intermittant C-Diff problem (yet another)

[heckboy]

So I have had intermittent center diff. problems like most everyone here. I have used the search function and read tons of postings.
My center diff is intermittent. I have been unable to find a pattern. Seems like when the truck is cold it works most of the time. When the truck is warmed up it works 25% of the time.
Troubleshooting the Toyota FJ80 Land Cruiser Center Diff Lock (CDL) | Pacific Northwest Backroad Adventures . When it is working the light comes on instantly. When it is not working I can drive in 4l for 15min. and it still won't engage.
I took out the diff lock control relay (behind the kick panel) and it failed the continuity tests. A call to CDan and $150 it was replaced. Problem still lingers.
Paperclip vs. 4wd indicator switch = positive light. Switch removed and it failed continuity test. Cleaned the heck out of it, put it back in and it worked for awhile and then failed. Replaced the switch, c-diff worked like a charm for a day, then became intermittent.
L4 switch removed and checked and continuity is fine.

So when it is working it works fast and easy. When it is not working, nothing I do can make it work. The next step it to bust into the actuator motor, I hesitate because
A) The diff. works great when it is working
B) It seems to get better for a bit, when I mess with the electrical system

Any thoughts? Sticky actuator motor or electrical gremlin?

 

[heckboy]

1993 fzj80

 

[Tools R Us]

When it doesn't lock, does the actuator motor run?

 

[heckboy]

I hear everything "click" up front, but I don't really hear the actuator. I am considering hitting the motor with a BFH to see if it will engage (bad idea?).

 

[Tools R Us]

I hear everything "click" up front, but I don't really hear the actuator. I am considering hitting the motor with a BFH to see if it will engage (bad idea?).

BFH probably isn't the best idea. My first test is always; does the motor run? If it runs, the problem is in the shifting side, if it doesn't then it electrical, position switch, bound motor, relay, etc.

 

[heckboy]

How do you test if it is running?

 

[Tools R Us]

How do you test if it is running?

Engine off, key to run, get under the rig close to the transfer, have a helper hold the brake, trans in N (only needed if the transfer needs to be shifted), shift the transfer or push the CDL switch. Each time the switch/shifter is operated the actuator motor should run for a second or so. Be aware that when shifted the rig could roll, so take proper precautions.

 

[Ebag333]

My center diff is intermittent. I have been unable to find a pattern. Seems like when the truck is cold it works most of the time. When the truck is warmed up it works 25% of the time.

Metal expands when hot. When cold there is more room/play for it to engage in. I've noticed the same thing with my truck and the truck.

When it is working the light comes on instantly. When it is not working I can drive in 4l for 15min. and it still won't engage.

How are you driving to try and engage it?

My rear diff was extremely sticky. I drove probably for hours (over the course of several weeks) trying to get it to engage on dirt and gravel. It never kicked in. Finally, a buddy of mine (CJF) suggested trying it on pavement before I tore into it. It did finally engage, but remained sticky for a long time (and was difficult to get engaged).

After several months of engaging/disengaging it a fair amount, it's finally working pretty decently, but it is noticably slower than the center or front diffs (the front locks up almost instantly almost every time).


It really just sounds like it's sticky. The was like that when we first got it, but using it a lot loosened it up and now it works like a charm.

When you can drive it and get it to engage, I would just repeatedly engage and disengage it at least a dozen times. Obviously wait until it's fully dis/engaged before cycling it. If you can't get it to go in after a few tries, don't try and force it, just wait until you have time for another go at it.

Driving side to side and reversing can help get it in (or out) too.