Center diff locking (1 Viewer)

[fjbj40]

I followed the instructions for locking center diff, but it’s not acting like it should.

I started truck, shifted to low, but I did not get the “ABS and diff lock” light.

ABS light comes on when I first turn on key but goes out in a few seconds.

I do not have a ctr diff switch, yet. But I thought it should lock if I did the low, get lights, pull 30 amp diff fuse?

 

[BILT4ME]

I followed the instructions for locking center diff, but it’s not acting like it should.

I started truck, shifted to low, but I did not get the “ABS and diff lock” light.

ABS light comes on when I first turn on key but goes out in a few seconds.

I do not have a ctr diff switch, yet. But I thought it should lock if I did the low, get lights, pull 30 amp diff fuse?

Yes, if your fuse is good, you should get the light when placed in Low Range (Assuming you do NOT have a CDL switch or Pin 7 mod.)

The fact that you have a 93, I think you DO have a CDL switch on the dash.

Also, you may need to actually move the truck to get it to engage.

 

[fjbj40]

Yes, if your fuse is good, you should get the light when placed in Low Range (Assuming you do NOT have a CDL switch or Pin 7 mod.)

The fact that you have a 93, I think you DO have a CDL switch on the dash.

Also, you may need to actually move the truck to get it to engage.

No CDL switch

 

[ZackR]

Start with the switch on the transfer case (its near the top, accessed from the passenger side). Disconnect the switch and short the leads on the wiring harness together and see if the "center diff lock" light comes on when you are in low range. If it comes on then the switch on the transfer case is likely faulty. You can get OEM or one from NAPA.

Slow to display Center Diff Lock/ABS light.

 

[fjbj40]

Start with the switch on the transfer case (its near the top, accessed from the passenger side). Disconnect the switch and short the leads on the wiring harness together and see if the "center diff lock" light comes on when you are in low range. If it comes on then the switch on the transfer case is likely faulty. You can get OEM or one from NAPA.

Slow to display Center Diff Lock/ABS light.

Well I know the bulb works! Decided to pull inst panel and it’s in there! Put power to bulb and it lights up

Kill 2 birds one stone, D light is out so will change that.

Only took 10 mins to get it all apart! Don’t know why people say it’s hard

 

[fjbj40]

Start with the switch on the transfer case (its near the top, accessed from the passenger side). Disconnect the switch and short the leads on the wiring harness together and see if the "center diff lock" light comes on when you are in low range. If it comes on then the switch on the transfer case is likely faulty. You can get OEM or one from NAPA.

Slow to display Center Diff Lock/ABS light.

Bingo brother! Switch dead, tried cleaning it, could get it to function but only at full compression. No bueno, new Beck and Arnley p/n 201-1788 going in.

Thanks mister

 

[fjbj40]

Switch replaced, still no lights

So I checked new switch when installed and in low, no continuity? So I jumpered the plug, ABS and Diff light comes on

So I guess something in the motor is no engaging. I hear the motor cycle when I move the xfer shifter from high to low.

I know there is a gear in there that is spun by the motor and it looks like the only way to access the motor is to drop the xfer case or lower tranny?

 

[ZackR]

Its worth reading most of this CDL actuator thread... but start here per the late @Tools R Us advice to see if the actuator motor is working:

CDL Actuator Fun

 

[BILT4ME]

Also, the light and he motor are NOT connected. One does NOT need the other to activate. They are two "separate" circuits.

 

[RayRay27]

I followed the instructions for locking center diff, but it’s not acting like it should.

I started truck, shifted to low, but I did not get the “ABS and diff lock” light.

ABS light comes on when I first turn on key but goes out in a few seconds.

I do not have a ctr diff switch, yet. But I thought it should lock if I did the low, get lights, pull 30 amp diff fuse?

Did you try driving it once you shifted into Low? It may take a few feet of driving to have it actually engage. Before you start pulling fuses and running down a rabbit hole, try driving it around once you have shifted into low range.

 

[ZackR]

Did you try driving it once you shifted into Low? It may take a few feet of driving to have it actually engage. Before you start pulling fuses and running down a rabbit hole, try driving it around once you have shifted into low range.

This is a great point..... mine usually takes about 10' of driving to engage, and the CDL light does not come on until it engages.

 

[ZackR]

In addition... if it hasn't been used in a long time it might need to be "exercised". Find a dirt road and drive for a bit in high range, then low, and keep switching back and forth.

Once you have a CDL switch installed on the dash it's easy to do this on the fly without having to switch from high to low range.

 

[fjbj40]

I put it in low and drove it for 1/2 mile, no joy.
Will find a gravel rd and try it again.

Thanks folks!

 

[fjbj40]

Been reading the CDL link that @ZackR posted.

So my motor runs, relays click, electrical circuit is good as I jumped the diff lock switch and lights came on.

So does that mean that the shift rod that moves the front shift fork is seized?

Seeing the motor turns springs which wind up and the springs are responsible for moving the driven gear how are you supposed to free it up?

Or is it the driven gear that is stuck and not the shaft?

Guess I will lower the xfer case and pull actuator and see what’s up!

Wish me luck

 

[baldilocks]

Good luck

 

[fjbj40]

Actuator out, stupid easy, 30 mins work!

Anyways, zero corrosion, motor gear turns when xfer shifted. I can reach in and spin the driven gear by finger, not stuck in either way.
Gear rotated about 180 degrees.

I pulled the actuator off with lever in H. When I was removing it I heard a spring lightly go twang?

So I am going to remove both driveshafts and try and spin the outputs to see if I can get it to engage by hand.

I think this actuator has been off before and maybe it was installed incorrectly?

Can I just jack one rear tire and spin that to try and engage instead of removing the driveshafts? Thought I read that somewhere?

 

[baldilocks]

I once removed the actuator without putting it in the locked position and problems ensued. However, I was disassembling the unit for low range gears and spool install, you are not. I was unable to remove the driven gears so this may not apply to you, not yet anyway....

 

[fjbj40]

I once removed the actuator without putting it in the locked position and problems ensued. However, I was disassembling the unit for low range gears and spool install, you are not. I was unable to remove the driven gears so this may not apply to you, not yet anyway....
View attachment 2324142

Thanks, I have the FSM, why anybody would not one is beyond me!

Anyways.....success !!

Sure enough, whoever was in there before did something incorrectly. I suspect fork not locked but CDL motor in locked position!

I jacked rh rear, spun driven gear by hand while moving tire with foot. I could put my pinky down the hole for the front locked switch and sure enough the ramp on the shaft was now up where it was supposed to be. I then screwed in the switch and verified continuity. Plugged in switch and had lights!
Just put it back together and cycled it 5-6 times, light off, light on every time.

With the tranny down 2” there is plenty of space to RandR the actuator.

Thanks everybody for the help. Now onto front driveshaft and try to diagnose whining noise!