locked center diff?

[fernandol]

Hello to all,

I have a 95 fzj80 with 167,000 miles on it.

I have made 7,000+ miles to it since I got it with no significant issues. It has suffered from vibrations at around 70 mph since day one, I attributed this to the tight angle the front u joint was working on due to a 2" lift installed by the first owner. I installed caster correction bushings and the angle of the u joint improved but the vibration persisted so had the tires balanced, the guy in the tireshop told me that my tires, 315 70 16, where always going to bounce a bit because they are too wide for the original alloys, had him balance them any way and the vibration problem improved but did not go away.

I decided to remove the front driveshaft to see if it was the source of the problem, and not been used to fulltime 4x4 with center diffs, I removed it and drove the truck, the vibration persisted, so I am beggining to agree with the guy from the tire shop. Anyway I have not yet reinstalled the front driveshaft and have been driving the truck daily for about 2 weeks without issue.

Today reading another thread I realized that my truck should not move with the front driveshaft removed because of the central diff, unless the VC is capable of sending enough power to the rear wheels? I tried turning the front coupler with the transmission in neutral and it does not turn freely, it tries to turn in conjuction with the rear drive shaft, I guess this means my center diff is stuck locked. I tried running it in L4 and then again in H4 but nothing happened, in L4 the difflock light comes on and in H4 it turns off just like it should.

What are the different causes for this? can it be just an electrical problem with the elocker? how can I rule out the different possibilities?
Could it be a problem with the VC instead of the center diff?

I will highly appreciate any help.

Regards

Fernando

 

[-Spike-]

Did you notice any power loss when you removed the front driveshaft? Is the truck sluggish off the line? Honestly, I wouldn't expect it to move for a few seconds at least, if at all.

The CDL light on the dash working indicates that the locker actuator is moving. I'm not sure if it's possible that the fork is no longer attached to the actuator, and it would have had to become unattached when the locker was engaged. I can't remember exactly which part hits the switch that lights the dash light but I think it's the fork itself. That would mean that it's not the locker putting all the torque to the rear.

-Spike

 

[fernandol]

Did you notice any power loss when you removed the front driveshaft? Is the truck sluggish off the line? Honestly, I wouldn't expect it to move for a few seconds at least, if at all.

I notice no difference with or without the driveshaft

 

[-Spike-]

Dunno what to tell you. Perhaps someone else will have a clue, 'cause I don't.

I have seen a truck with the rear end off the ground, with a non-functioning locker, and it didn't move, didn't even seem to try to move, even after revving the engine a bit and spinning the rear tires for a while. We expected the VC to add more power to the front as it warmed, but it never seemed to. It may have been providing some power to the front, but I would think the power loss would be noticeable right away.

-Spike

 

[Grench]

Just when I though that the odds of a Diff Lock staying locked when not in low without a CDL switch was 1:10,000... Guess I'm eating those words.

The behavior you're showing shouldn't be possible without a CDL switch or something broke that shouldn't break IMHO.

2x what Spike said.

Did you say something to annoy the parts shaman?

 

[fernandol]

I can see some red silicon form-a-gasket showing that the transfer case has been opened, could it be that the first owner did something in there to keep the diff locked? I know that for the last few years he had the truck, he only used it for hunting in his Texas ranch, maybe he had problems with the VC and decided to remove it and permanently lock the center diff in the process? I do not see the logic on this if you can lock it at will with a 30$ cdl switch.

It looks like I am destined to drive with my front driveshaft straped to the back of my truck until I reach the trail.https://forum.ih8mud.com/images/smilies/crybaby.gif

 

[-Spike-]

I don't want to talk you into damaging your truck, but if it were mine I'd see if it were possible to turn the t-case front driveshaft flange by hand (truck off and cool) or with some kind of tool for leverage. If it moves, I'd put the front shaft back on. If it didn't, I'd probably put it on anyway, and pay close attention to how the truck behaves. I'd put it through some turns with the windows down, listening for tearing rubber.

First though, I'd give the board a day or two to come up with some ideas.

-Spike

 

[CJF]

Interesting!

Anyone with a 93-97 feel like running the test I described here just to make sure it acts the same as a 91-92?

https://forum.ih8mud.com/showpost.php?p=1439001&postcount=16

 

[fernandol]

I still haven't installed the front drive shaft so tryed turning the front coupler by hand with the transmission in neutral, the engine off and the truck had been resting for about half an hour, nothing happened, so I used a wrench for leverage and the whole truck moved when I tryed turning the coupler, the front coupler moves in conjuction with the rear driveshaft.

 

[-Spike-]

Wow. I got nuthin' else, anybody else want to try?

-Spike

 

[Grench]

Go with what you know?

Wow. I got nuthin' else, anybody else want to try?
-Spike

Its locked, right?

The only other thing I can think of is if the front side of the transfer case is locked up or binding. This could cause the vibrations that started the whole mess.

Don't do the following unless at least 1 other agrees that it is safe. Here's my idea.
1. Put your front DS (drive shaft) back in (for now.)
2. Chock the back DS (driver side) wheel.
3. Chock the front PS wheel.
4. Put the front DS (driver side) on a low jack stand. You only need the tire 1/2" off the ground for this.
5. Put the back PS on a low jack stand. You only need the tire 1/2" off the ground for this.
6. Put the trany in Neutral. Leave the transfer case in High. You did chock the wheels that are on the ground, right?
7. Grab ahold of the DS (driver side) front wheel and try to turn it. If you can, the PS rear wheel should turn as well. Keep all body parts out from under the truck. Remember that it is still in the air.

The question is, how hard is it to turn that wheel? It should be easy in this scenario regardless of if the CDL is locked or not. If it is hard to turn... Something more is going on.

Part B is to put the DS (drivers side) front tire back on the ground and try to turn the PS rear wheel that is in the air. Can you do it?

Part C is to put the PS rear back up and the DS (drivers side) front back down. Try to turn the PS rear wheel. Can you do it?

(This is all assuming that the vehicle doesn't have FR/RR diff locks or they aren't engaged.)

So, someone else say no? Spike? I'm reaching on a limb here. Do you think there is any chance the above might work?

 

[CJF]

7. Grab ahold of the DS (driver side) front wheel and try to turn it. If you can, the PS rear wheel should turn as well.

Did you try this yourself, or are you speculating? I believe your explanation is incorrect and incomplete. In the scenario you describe:

1) If the center diff is open (tranny in park, TC in 4hi), both wheels should spin, but in opposite directions.

2) If the center diff is locked, neither wheel will spin.

I think you were right the first time; sure sounds like, for whatever reason, his center diff is locked.

Curtis

 

[Grench]

You're right. I think I am too. I was looking beyond simply calling the t-case 'locked' and am looking for a binding on the front or rear output from the t-case. What if one of the outputs is binding? Wouldn't that give a locked-like scenario without the CDL light coming on?

Someone correct me if I have it wrong...

If the trany is in park, transfer in H, and it is locked or not locked they won't (shouldn't ) turn with a single wheel up.

If the trany is in neutral, transfer in H, and it is locked, the wheel on the front and the wheel on back are linked and should both turn in the same direction.

If the trany is in neutral and transfer in H, and it is not locked a single wheel in the air should turn by itself.

If need be, I can (literally) jack around with my truck this weekend and show examples.

 

[SUMOTOY]

1 of two scenarios here.

1) Center diff locked - my guess
2) VC all locked up causing center diff lock - not my guess.

I doubt there is 'binding', something would break. It's locked thru either the locker or the VC. Here's hoping it's thru the locker. Since you mention the guy was a hunter, maybe he figured to just lock the thing up without reading the mod options. IIRC, there is one prior to the 7pin mod that includes removing the diff lock light connector on the transfer case.

Me, I'd ck underneath the truck at the transfer case and look for a pulled connector on the diff, the one that activates the light. And/or ck for continuity thru the center diff lock light (burnt out or removed).

HTH and my .02

STJ

 

[-Spike-]

Me, I'd ck underneath the truck at the transfer case and look for a pulled connector on the diff, the one that activates the light. And/or ck for continuity thru the center diff lock light (burnt out or removed).

Only trouble with this is that he stated that in 4 low the light comes on, indicating normal functionality of the locker actuator and switch.

-Spike

 

[fernandol]

yes, the light does come on in L4 and off in H4 so we are guessing the actuator in the locker is working.
Maybe this guy had some problem with the vc or the locker actuator and decided to lock it permanently since he didn't use the truck on paved roads? I guess the only way to find out is to open it up and take a look inside....???

Hopefuly someone else will have another idea.

 

[fernandol]

Ok, it seems that I am stuck with a locked central diff for the moment and since I can't afford to drop the transfer case and see what's wrong because I don't have the time and the 80 is my only car, I think I will just drive it around town without the front driveshaft. It is a quick install anyway when I go out to the trail.

When I get the time and the extra cash I will go with a 4bt, NV4500 and a split transfer case from an fj60.

Thanks for all your inputs, I will let you know if I find out anything else.

 

[Grench]

You might consider installing a CDL switch (easy). My fear would be if you're out someplace and whatever is stuck causing you to be locked becomes unstuck and unlocked... Having the front DS and tools would work too. Driving home in low on the T case could be annoying.

 

[-Spike-]

You might consider installing a CDL switch (easy). My fear would be if you're out someplace and whatever is stuck causing you to be locked becomes unstuck and unlocked... Having the front DS and tools would work too. Driving home in low on the T case could be annoying.

LOL, hadn't thought of that, but yeah, definitely a good idea.

-Spike

 

[CJF]

You might consider installing a CDL switch (easy). My fear would be if you're out someplace and whatever is stuck causing you to be locked becomes unstuck and unlocked...

Dat's a good point!

Curtis