Advice needed: '94 fj80 involuntary ctr diff lock

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Aug 25, 2003

I'm a newbie here and need some advice:

My '94 fj80 with 97k on it has a strange habit of locking up the center diff (as if it's in 4L) after drives at hwy speeds of at least an hour or more.

My best guess is something is heating up inside the transfer case and is forcing an artificial engaging of 4L. This makes it very difficult to turn at low speeds and I'm afraid I'm putting significant wear on something when I do.

When I suggested replacing the viscous coupling unit, the dealer kind of looked at me funny and said "we don't do that -- we'd only replace the whole transfer case." At about $4,000!! They could also do an "overhaul" which would run more like $3,000. Spending this kind of money could get me a head start on a newer LC.

I'm wondering if anyone could shed some light on this or suggest a less expensive, yet effective, fix. I'd like to keep the truck for quite a while longer (I'm not a big fan of leather interior on newer models and I like the relative simplicity of the 80 vs. the new 100s).

Many thanks in advance!
Well my first suggestion would be to get the center diff lock switch, then disconnect the wire on top of the T-Case. Could be that when things heat up, that connector on top is in fact locking the T-case automatically, as you describe. Of course this is just a guess, but the risk of doing this is minimal (about $65 for the switch + shipping) and you needed to get the switch anyway.. here it is

hope that helps, good luck.
You could start by just unplugging the connector Nakman mentioned. Instructions on the site he posted, shouldn't take 5 minutes. If it works, get the switch.
There goes another t-case :eek:
You say when your driving and the t-case gets hot and you turn the wheels feel like you are in 4WD?
You have a failed VC. I hade the same problem. After driving at 65+mph the vc would lock up. After it cools it would be fine.
There are several way to go;
remove the VC and drive it that way
new t-case bout $2100 and you replace it your self.
get a used one
get a new used one from $1500 plus shipping and return
shipping unless keep the old t-case, then there is a 100 core charge.
sell or trade it

I went the new t-case and installed it my self.
Don't have it rebuilt as the VC is $700+
Don't get a rebuilt one as they use the old VC.

You can drop and install it with a tranny adapter on a floor jack.
My new t-case started to leak, Toyota replaced it with no problems, I hade to drop and intall them though.

:) Thanks for the quick insight guys!

It sounds like I have the identical symptoms as Kurt did. Hwy driving locks it up and cooling for 20 mins would be fine.

Kurt, what would happen if I just remove the VC? Do I lose my fulltime 4WD? Do I lose all 4WD? Not just sure what the ramifications of that would be.

Also, is there a way to replace ONLY the VC unit, or does the whole transfer case need to be replaced?

And as far as installing a ctr diff switch -- I'm assuming that this allows me to manually turn on/off ctr diff locking? Would turning the switch off unlock the ctr diff even if it was heat-induced? Or is that just wishful thinking...

Thanks again for all the help!


The coupler is available by its self. It is a 41330-60010 and it lists for $1,122.44 A complete transfer case is a 36130-60661 and lists for $2,505.51

A "smart shopper" could buy the coupler for around 850 bucks and the transfer for about 1,900 bucks. In order to buy the transfer at that price, shipping to your door would most likely be additional.

If I was to do it again, I would remove the rear output shaft cover and remove the VC. THe only thing you would lose is If one wheel looses traction or is off the ground, you will be stuck. Adding the center diff lock switch will still lock up the t-case, so if you get stuck you can lock the t-case and get out. I have my old t-case apart and I don't see reason why you couldn't run without it. It just slides on the rear output shaft.
One other, way out there thing, you could try is;
get lockouts for the front hubs (i don't know if any will work)
get center diff lock switch and unlock the hubs and lock the center diff.
This might be a thing to try. This way when weather gets cool/cold out, you could lock the hubs and see if the VC still locks up.

Dan ,How does one get to be a "smart shopper"???
[quote author=landtoy80 link=board=2;threadid=4650;start=msg35773#msg35773 date=1062035943]

Dan ,How does one get to be a "smart shopper"???

Kurt, that's as easy as fallin' off a log. :D

PM me and I'll tell ya ;)

I like the idea of removing the VC unit and using the CDL switch to engage the front. Question is, how difficult would it be to install locking hubs? I understand the center cap on the wheel needs to be removed for access but is this doable on a '93-'97 vehicles? Talk about having your cake and eating it too!

When you remove the VC the t-case will become like a open diff. If one of either the front or rear wheels are off the ground, you will be stuck. I see no reason to add lockouts if you remove the VC. But adding lockouts and locking the canter dif switch will bypass the VC.
One not about not having the front locked. I removed my front drive shaft untill I replaced the t-case, when I ingaged in D or R the whole vehicle would rise or lower. I don't know if it has to do with my old shocks but id doesn't do it with the front shaft on. It is like I have a Range Rolover with air bags. The torque on the diff must counteract each other.

[Dan ,How does one get to be a "smart shopper"???

Kurt, that's as easy as fallin' off a log.

PM me and I'll tell ya


THe last time I fell off a log, I got hurt :'( :D

Crash helmet maybe? ::)
[quote author=landtoy80 link=board=2;threadid=4650;start=msg35928#msg35928 date=1062083879]
Cup! :eek:

OH, you fell that way :'(
Send me a PM..I may be able to help you get a replacement t-case.

would be used, but I have a post to finalize if it is a VC t-case or the earlier geared t-case.
I'm not sure what I should do at this point about my VC unit/tcase going bad. I sure wish I knew of a good LC guru in my area (Phila/PA/NJ).

If I replace the tcase and have it installed by the dealer, I'm looking at $3-4,000. VC unit only would maybe be $1,000 less. They tell me I also need new brakes, front rotors (warped and only 1.5 years old!!), and my front axle is leaking (per dealer).

I absolutely love the truck (the rest of it is in almost mint condition), but I'm thinking I can put this money towards a newer one and it may make more sense.

Any thoughts? I'd love to keep the one I have if it makes sense...thanks for the help.
First you should remove the front drive shaft. You will need a center diff lock switch so you can lock the t-case and drive it without the front drive shaft. You are doing damage driving on hard pavment that way. I drove mine 80 mi at 73mph and the t-case got so hot it took 4 hrs before it cooled down. When I say cool down, that is the vc is cool enough so that it is not locked.

If are not going to do the work your self have some one remove the rear output part of the t-case and remove the VC and put the output case/shaft back on. You wont have true AWD but it is better than nothing.
[quote author=kallen123 link=board=2;threadid=4650;start=msg38982#msg38982 date=1063041195]

If I replace the tcase and have it installed by the dealer, I'm looking at $3-4,000. VC unit only would maybe be $1,000 less. [/quote]

In case you didn't notice, somebody else in this thread is able provide you a new transfer case for 1900 + shipping charges. Now all you need to do is find a qualified mechanic that dosen't charge dealer labor rates.

If you don't get any leads on a mechanic in this forum, ask on the 80scool yahoo egroups mailing list.

Any tranny shop should be able to drop the t-case. All you do is remove the drive shafts some plugs and the bolts. You don't need to remove the tranny. If I can do it anyone can.
[quote author=landtoy80 link=board=2;threadid=4650;start=msg35148#msg35148 date=1061909813]
There goes another t-case :eek:


I was reading the original post and I said to myself...

"Self, sure sounds like the problems that Kurt was having over in Wisconsin"

I remember how frustrated you were and you tried just about everything...seems like you had just purchased the cruiser and were trying to iron out the bugs, right?

It is a neat thing to use first hand knowledge to help others, isn't it? Although, I usually like it when someone would tell me it is a broken $.25 wire instead of a $2k transfercase :'(

-just a lurking and a lookin...too busy keeping all the cruisers running

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