If my rear locker never engages but my center and front do (according to the light in the dash)... what should I look into getting repaired or fixed? (1 Viewer)

[Perfected]

Title.

I could never get my rear locker to engage but the center and front do fine I believe.

The rear locker light just flashes forever and never turns solid.

What should I look into getting replaced or repaired?

 

[Rwhat]

How do you know it doesn’t lock? Besides looking at the flashing light?

Have you tried to jump the E-locker motor to verify that it’s operational?

Did you use the search function?

 

[Perfected]

How do you know it doesn’t lock? Besides looking at the flashing light?

I guess I dont know for sure. The light is the only indicator I have. I know the center locks fine because it can go into 4low fine I believe and the front may or may not be locking but it does turn solid.

Rear flashes forever though no matter what I try regardless.

Any tips?

 

[Rwhat]

You can verify that the rear doesn’t lock up? Start with that. If it does actually lock up, then if I remember correctly the indicator switch in the locker is possibly bad.

 

[Perfected]

You can verify that the rear doesn’t lock up?

I can verify that the light flashes forever which is my only indicator, correct? If its not solid its not locked, correct? Or is it possible that it could be locked and still flashing?

 

[pigmony]

Put the vehicle on jack stands and rotate one of the rear tires by hand. If the opposite rear tire rotates in the same direction, the locker is engaged. If the opposite rear tire rotates in the opposite direction, the locker is not engaged.

 

[BILT4ME]

The F/R lockers will not lock until the CDL is locked.
The front will not lock until the rear and CDL is locked.
The rear will not lock unless the CDL is locked.

I believe the indicator lamp on the dash is separate from what is actually happening under the truck. Do what was suggested above in order to properly diagnose. I believe there is a section in the FSM that walks through this.

 

[TXLX100]

Easy steps to try....

Turn the rear locker on with key in accessory, to determine if there is audible click from rear locker. If no noise, check the wiring and harness at the locker, make sure no corrosion and pins are seated in the harness. If that doesn’t work, remove rear locker actuator and test it on front locker harness. If the locker is inop, it probably has internal issues and needs to be rebuilt or replaced.

 

[retrofive]

The F/R lockers will not lock until the CDL is locked.
The front will not lock until the rear and CDL is locked.
The rear will not lock unless the CDL is locked.

I believe the indicator lamp on the dash is separate from what is actually happening under the truck. Do what was suggested above in order to properly diagnose. I believe there is a section in the FSM that walks through this.

Not necessarily true if you dive in to the logic of the f/r ecu. But I will leave that for the other locker threads.

 

[Perfected]

Easy steps to try....

Turn the rear locker on with key in accessory, to determine if there is audible click from rear locker. If no noise, check the wiring and harness at the locker, make sure no corrosion and pins are seated in the harness. If that doesn’t work, remove rear locker actuator and test it on front locker harness. If the locker is inop, it probably has internal issues and needs to be rebuilt or replaced.

Perfect! Thank you I will try this later.

The F/R lockers will not lock until the CDL is locked.
The front will not lock until the rear and CDL is locked.
The rear will not lock unless the CDL is locked.

I believe the indicator lamp on the dash is separate from what is actually happening under the truck. Do what was suggested above in order to properly diagnose. I believe there is a section in the FSM that walks through this.

Thank you as well.

 

[ppc]

The F/R lockers will not lock until the CDL is locked.
The front will not lock until the rear and CDL is locked.
The rear will not lock unless the CDL is locked.

I believe the indicator lamp on the dash is separate from what is actually happening under the truck. Do what was suggested above in order to properly diagnose. I believe there is a section in the FSM that walks through this.

Partially correct.
"The front will not lock until the rear and CDL is locked." The confirmation of the lock completing on the rear (light stops flashing) is totally independent of the operation of the front locker. The only constraint on the front locker is the CDL needs to be confirmed as locked (CDL dash light on). The fact the RR/FF locker dash switch rotates first position to rear and second position to front/rear. What the OP states in this post his observations support this.

To the OP, you can test the indicator/sensor circuit functionality by pulling the connector at the rear axle sensor and short the contacts. The dash light should light without flashing. If that is the case then you should remove the sensor switch and test continuity when exercising the switch.

Check out this link from @george_tlc

CDL Sensor/Switch

 

[subzali]

Mine was doing exactly as you describe. It turned out that the springs, shaft, and toothed gear inside the locker were no longer well lubricated. Old grease had gotten dirty over time and dried up. But it could be several things including limit switch, seized actuator rod, motor magnets, etc.

search threads on rebuilding the rear locker by @landtank, @Tools R Us, @RavenTai, @clownmidget, and maybe a few others and there are some great descriptions and pics. Gotta just dive in and start pulling it apart and see what’s up inside.

 

[Perfected]

Mine was doing exactly as you describe. It turned out that the springs, shaft, and toothed gear inside the locker were no longer well lubricated. Old grease had gotten dirty over time and dried up. But it could be several things including limit switch, seized actuator rod, motor magnets, etc.

search threads on rebuilding the rear locker by @landtank, @Tools R Us, @RavenTai, @clownmidget, and maybe a few others and there are some great descriptions and pics. Gotta just dive in and start pulling it apart and see what’s up inside.

Thank you King.

 

[Wrencher93]

FWIW, mine was doing similar things (rear diff light would flash but didn't want to go solid) and it turned out that I just needed to exercise them more. Pulled the 80 into the yard and turned all the lockers on and off in the proper sequence until everything worked more smoothly. Try turning to lock the rear if you haven't. I wasn't giving mine enough differential motion to lock - hence the blinking.

 

[jonheld]

I believe there is a section in the FSM that walks through this.

Yes. In the 96 FSM page SA-101 has a full diagnostic of the diff lock system. Just follow the procedure in the FSM to diagnose.

 

[Azca]

Before going to all the trouble of testing and tearing things apart, take it to a flat dirt road/area you can turn around in.

1. Place it in 4 low
2. engage the lockers.
3. While moving slowly, turn the rig.

The lockers, front and rear, have cogs that must mesh to engage. I do not recall if the front or back are larger but, it can take a fair amount of distance, (usually less than 20 to 30 feet) for the cogs to mesh and engage the lockers at which time the blinking locker light will go solid. ToolsRus had a good write up on this quite a ways back. Once engaged, it may be necessary to repeat this procedure to unlock them. If this works, there is nothing wrong with the lockers. Just remember to exercise them every few thousand miles....