Another center diff locking problem...

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Kbug

Kbug

10 Year
Joined
May 5, 2013
Threads
11
Messages
65
Location
Frederick, MD
So I've searched back quite a ways and haven't been able to find anything that has helped me yet. I have a 92 with the factory CDL switch on the dash. The last time I used the CDL was a few months ago when I was doing some light wheeling, I switched the truck into Low range and the diff lock automatically came on. When I was done and I shifted the truck back into High range, it took a bit of driving before the diff finally unlocked (about half a mile). Fast forward to today when I was doing some more light trail wheeling and shifted my truck into Low range, diff locked, all was good until I shifted back into High, but the diff lock wouldn't disengage. I know the diff is still locked because the truck binds up when turning. I've since put about 40-50 miles on the truck, tried reversing it, driving over bumps/curbs, driving in an S shape, unhooking the battery, removing the diff fuse, tried shifting it back and forth between Low and High range, tried engaging and disengaging with the CDL dash button, and so far nothing has worked. Truck is my daily so I really need to fix this ASAP
 
How long have you had the truck? Did previous owner ever use the 4lo feature much? Could be binding from non use lack of use. As to how to get it to unlock sorry I'm no help
 
Got the truck about 5 years ago, PO beat the hell out of it. I think he ran it with the diff locked all the time (possibly because of the problem I'm having now) and stripped the front gears. I took it to a shop and had everything fixed/replaced and it was fine up until now.
 
With truck in high range....accelerate (on flat ground) to about 10 mph, then let off the throttle (to coast) and try to activate the CDL. Also try it in neutral. The idea being you are taking the load off the drive-train giving the CDL the best chance to lock or unlock.

Sounds like it is sticking from non-use.
 
  • Like
Reactions: RFB
Well I drove all over my neighborhood trying to disengage it and it still wouldn't unlock.

Couldn't removing the front driveshaft and driving with the diff locked still cause damage though?

I don't have a way to test the old one and it wasn't blown, but I replaced it with a new fuse anyway
 
Just a thought, you are trying to release the Center Differential with the transmission in P or N, right? If the transmission's in gear, the transfer gears can't mesh.

And yes, you're really not well advised to drive around the neighborhood with the CDL engaged. It shouldn't take more than a couple of turns of the wheel to disengage. If that doesn't work, something's wrong. It's better to get the truck off the ground than to drive it.

This is a completely mechanical system, so if the actuator motor is working, and the CDL won't disengage, you have an internal fault.

You say you replaced the front gears, do you mean the front axle differential gears, or the front gears in the transfer case?
 
Yeah I've been trying it in park or neutral. Is it possible the actuator motor went out?

And tbh I don't even know. I was 14 at the time and barely knew how to change a spark plug back then, I just knew the 4WD wasn't working. My dad took it to a shop and had it done.
 
OK, no problem. Next question. Do you have a '92 FSM?

Here's the motor actuator inspection procedure:
upload_2017-11-16_14-52-14.webp


upload_2017-11-16_14-52-38.webp
 
I'd make sure this isn't the problem, before I drove it again. I know you said this is your DD, and I've been there (I lost my first 80 to a xmsn failure, it was my DD and I couldn't wait to have it fixed), but if you have a small problem, like a weak spring on a shift fork, and you drive it the the CD locked, you're looking at rebuilding the xfer, worst case. That's neither easy nor is it cheap.

These things are tough, but they can be broken.
 
Kbug said:
Yeah I've been trying it in park or neutral. Is it possible the actuator motor went out?
Click to expand...

Possible, but try doing this specifically in N - get all the bind out of the drivelines right down to the parking pawl. Pack a lunch & cycle the crap out of it - sounds like it's been unused for longer periods.

I'd start it, put the trans in N & cycle the transfer case between N & L plenty of times to get it to have plenty of opportunities, after 5-6 N&L cycles then bump it into D & creep forward, back to N & repeat.

Ideally you would be able to drive it ahead of time to warm up the entire powertrain, but that sounds like a bad idea as it sits.

If it was my rig in this situation, I'd warm the powertrain by letting it run/idle for ~20mins in D but with the transfer case in N, at least splash that TC oil around a bit before expecting the CDL to cycle. I'd do that before the 2nd paragraph.

Can you run a multimeter & check for power @ the CDL plug?
 
Malleus said:
Just a thought, you are trying to release the Center Differential with the transmission in P or N, right? If the transmission's in gear, the transfer gears can't mesh.

And yes, you're really not well advised to drive around the neighborhood with the CDL engaged. It shouldn't take more than a couple of turns of the wheel to disengage. If that doesn't work, something's wrong. It's better to get the truck off the ground than to drive it.

This is a completely mechanical system, so if the actuator motor is working, and the CDL won't disengage, you have an internal fault.

You say you replaced the front gears, do you mean the front axle differential gears, or the front gears in the transfer case?
Click to expand...

I'm able to lock/unlock the center diff while driving in high range (using the CDL switch). I've done this many times around 30mph while on dirt roads and it locks and unlocks easily (no noises or anything wierd happens). Before the CDL switch was installed when I selected low range (in park or neutral) it took maybe 5-10 feet to lock/unlock depending on the terrain. I assume if it wasn't supposed to work while driving the light would flash or indicate some kind of error.

As folks have mentioned if its taking more than block to lock/unlock something isn't right. Once you get it fixed be sure to "exercise" the system on a regular basis to keep it working smoothly. I try and activate mine at least once a month.
 
ZackR said:
I'm able to lock/unlock the center diff while driving in high range (using the CDL switch). I've done this many times around 30mph while on dirt roads and it locks and unlocks easily (no noises or anything wierd happens). Before the CDL switch was installed when I selected low range (in park or neutral) it took maybe 5-10 feet to lock/unlock depending on the terrain. I assume if it wasn't supposed to work while driving the light would flash or indicate some kind of error.

As folks have mentioned if its taking more than block to lock/unlock something isn't right. Once you get it fixed be sure to "exercise" the system on a regular basis to keep it working smoothly. I try and activate mine at least once a month.
Click to expand...


^^^^^^^^ Same with mine. Before the CDL switch it would take just a bit for it to engage or disengage, sometimes even requiring 'coasting' (little to no load on the drivetrain) for it to disengage.

After adding the CDL switch and doing the pin 7 mod, I actually use it more and can engage/disengage in gear or out of gear, transfer case in HI/LOW doesn't make any difference.

I am thinking the OP might have an electrical issue with his (poor connection, low voltage, etc).
 
Unfortunately I don't have a multimeter but I can borrow one, just won't be able to do it till tomorrow. In the meantime the truck is staying parked, my parent's loaned me their truck for the next few days. I've already tried cycling between high and low range a bunch of times but I suppose it wouldn't hurt to try again
 
Kbug said:
Unfortunately I don't have a multimeter but I can borrow one, just won't be able to do it till tomorrow. In the meantime the truck is staying parked, my parent's loaned me their truck for the next few days. I've already tried cycling between high and low range a bunch of times but I suppose it wouldn't hurt to try again
Click to expand...

Even a cheapo multimeter is better than nothing. When you are out and about pick one up and keep it in the glovebox.
 
Kbug said:
Couldn't removing the front driveshaft and driving with the diff locked still cause damage though?
Click to expand...

I don't think anyone addressed this, so NO, driving without the front drive shaft AND THE CDL LOCKED won't cause damage.

Driving with no front drive shaft and the CDL UNLOCKED may cause damage. In the case of your '92, I think you just won't go anywhere since you don't have a viscous coupler in your transfer case.

This is one reason why people like to add the CDL button in later rigs. If you damage a drive shaft, you can remove it and activate the CDL, then limp home in rear wheel drive or even front wheel drive.
 
Are your tires the same size, brand and type from front to rear and left to right?

Are your tire pressures equal in all 4 tires?

If you have low tires or mismatched tires, it will create a drive line bind. That will make it hard to lock/unlock. That being said, I would have thought that driving around the neighborhood that much would have allowed it to release.
 
You must log in or register to reply here.

Share this page

IH8MUD Forum | Toyota, Lexus & Off-Road Community
Community platform by XenForo® © 2010-2026 XenForo Ltd.

© 2000-2026 Tie Rod Media LLC

Back
Top Bottom