03 4runner front diff not engaging

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Hi Martin,

I apologize I won't be able to offer you the most helpful answer on this issue. I have escalated your question so that it will be taken care of an  another expert who can assist on this 4Runner  . We appreciate your patience. You will be notified via email when a new Expert contacts you for continued support for your issue.

Thanks

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Before we get started, I want to remind you ExpertHelp.com is an independent professional support company. We do not have any affiliation with TOYOTA nor are we paid to provide support on their behalf. However, we have helped hundreds of customers with similar questions and believe we can help you too. OK, let’s get started! :)

 Hello Martin... how are you doing? I will have to ask you some questions to sort out the problem. Thank you

I see... how was it Martin?

Ok, have you tried disconnecting the battery Martin? If not, try to remove the positive battery connector and let it sit for 5 minutes before reconnecting it. Sometimes the current in the system needs to be flushed to get the electricals working again. Let me know of the result before we perform other solutions. I'll be waiting. thank you

Can you please try this.

- Put the truck in neutral

- Shift it to 4LO and see if it engages

- lock the CDL

- shift into drive and see how it drives

- put back in neutral and release CDL and 4lo

Have you replaced the transfer case actuator Martin?

Center Differential Lock

Ok, try the shifting procedure first Martin and let me know of the result. I'll be standing by. Thank you

Ok, I believe that the actuator is not out. I am suspecting the ADD (automatic disconnecting differential) system. You may print this page for reference Martin. There is a pneumatic device called an "actuator" attached to the front differential that effectively slides the driver side shaft out of the differential. On trucks that have ADD Toyota uses "live hubs" (see hubs section below). This means that both front half shafts and the front diff spin even in 2WD (but not the front drive shaft). There are a set of air bags inside the actuator that control the position of the ADD sleeve. This actuator will stay in it's current position until vacuum is applied to change it's position even if there is no vacuum at all. For 2WD operation vacuum is applied to driver side tube of the actuator and it holds the sleeve in the out position. 

When you engage 4WD a switch on the transfer case changes a set of air valves under the hood. This causes vacuum to be applied to the passenger side tube of the actuator and it pulls the sleeve over to the right and connects the drivers side axle shaft to the differential. Once the splines on the sleeve and the splines on the shaft are aligned the sleeve slides toward the passenger side and the front drive is engaged There are two switches that must be in the closed position for the 4WD light to come on. The first switch is controlled by the position of the transfer case shift lever. The second light is on the ADD actuator and it turns on after the sleeve has moved into the right (locked) position. 

ADD SYSTEM troubleshooting

The most common problem is damage, deterioration, or mis-routed vacuum hoses. To ensure the vacuum lines are routed properly, they are marked with either a blue or brown tracer stripe on the hoses. These hoses should match up with the corresponding VSV under the hood. In some cases during engine or collision repairs, these hoses get routed incorrectly or left disconnected altogether. 

When the transfer case gear shift is shifted into 4WD, the ADD system is actuated by the operation of the ADD solenoids located under the hood on the passenger side wheelwell. The solenoids are supplied voltage from the ADD relay which depending on the type of transmission the vehicle is equipped with, has it's ground completed by both a Transfer Position Switch and a Transfer Pressure Switch (V6 with automatic transmissions), or a Transfer Indicator Switch (4cyl.-- manual trans.). These solenoids control the vacuum signals to the ADD actuator which is mounted on the front axle. This actuator engages a sleeve inside the differential via an "intermediate shaft" which is attached to the driver's-side side gear shaft and clutch mechanism. 

If the ADD system does not properly engage the front drive mechanism, the first items to check are the vacuum supply hoses. First, look under the hood and locate the ADD solenoids. Ensure that the vacuum hoses are connected to the solenoids or vacuum switching valves (VSV) as they are commonly called by Toyota. Next, look at the hoses at both the differential and vacuum reservoir located in the R/F wheelwell. Make sure all hoses are connected and not torn, cracked, or otherwise in poor condition. Once the system is engaged or disengaged from 4WD, it will stay in that position. Basically, if the system is not functioning, the vehicle can be placed in either 2 or 4 wheel drive manually with a vacuum source for testing. If you plan to leave the ADD system disconnected you will need to apply vacume from the engine to make sure the front end does not unlock. 

Do you hear a beeping sound Martin?

Ok Martin, one reason why it's beeping is because it's not engaging. You can start from replacing the actuator itself

Try to open it and look if the actuator will look like this

Please let me know what you will find after opening the actuator Martin.

There it goes..... I suspect something is not right. Maybe there's a yard near you where you can purchase the whole assembly itself. You may use the other parts in the future incase something fails again.

This will cost $180 in ebay Martin

Is there anything else I can help you with Martin?

May I ask you  a little favor Martin

Dear Martin, It was a pleasure helping you with your Toyota issue today. Here is a summary of the resolution.

Issue identified : Front differential won't lock
Solution Implemented : Checked actuator assembly. Looking for deteriorated parts including the actuator. Found out that gear is broken which is causing the issue
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