Deep sand and no 4 wheel drive in my Prado = trouble. (1 Viewer)

[digitalbuck]

I e had my Prado for a few months but hadn't had it off road yet. So I drove a few hours to a national forest with 4x4 trails and planned to have a ball. It wasn't until I got in an uphill stretch of deep sand that I realized my front wheels weren't pulling. So I spent the afternoon getting stuck then wrenching out, getting stuck then wrenching out, times six. The indicator lights showed the hubs locked and 4 wheel drive engaged. I had no problem getting into low range or locking the rear diff. But those fronts just weren't pulling. Thoughts???

 

[AirheadNut]

In my experience, the hub lock light will come on sometimes even when the hubs aren't actually locked. My guess is that one or both of the hubs aren't locking. Mine both work, but they can be slow. I have had to push the button and then slowly move the vehicle forward or backward until they engage. Yours might need a rebuild.

 

[digitalbuck]

In my experience, the hub lock light will come on sometimes even when the hubs aren't actually locked. My guess is that one or both of the hubs aren't locking. Mine both work, but they can be slow. I have had to push the button and then slowly move the vehicle forward or backward until they engage. Yours might need a rebuild.

I dang sure did plenty of rocking back and forth when I was stuck!

 

[oldblue]

The Hub Lock light is on a separate wiring direct to the Hub Lock ECU, and the Electric hub motors are also wired direct to the ECU so they are on two separate circuits.

 

[GTSSportCoupe]

Almost guaranteed you've got problems with the hub electric brushes. Many of them are broken off or missing from not being properly retained when people take the hub/rotor off for maintenance. LOTS of threads on this here. I'm pretty sure no one puts the proper electric grease on the brush/slip ring when they take things apart either. This is why a lot of people switch to manual hubs. I've attached the hub service section from the 70 series repair manual for you.... Have fun.

 

[digitalbuck]

Thanks so much for that. Huge help.

 

[digitalbuck]

Here is some updated info. I can hear the hubs click in when I hit the button. But then as I start to drive I hear grinding. I think it's from the transfer case. I stopped, backed up, went forward and the grinding stopped. Next time I tried it did the grinding again. I stopped, put it into 4 low and the grinding stopped when I drove. But still no 4 wheel drive. But I don't think it's the hubs.

 

[GTSSportCoupe]

Here is some updated info. I can hear the hubs click in when I hit the button. But then as I start to drive I hear grinding. I think it's from the transfer case. I stopped, backed up, went forward and the grinding stopped. Next time I tried it did the grinding again. I stopped, put it into 4 low and the grinding stopped when I drove. But still no 4 wheel drive. But I don't think it's the hubs.

Check the vacuum actuated transfer case setup. On mine on of the little VSV's that engage/disengage finally failed and I had to replace them. I just used ones that matched from an emissions system on another Toyota. It could be also that your vacuum lines are messed up or leaking. Check that the vacuum lines from the vacuum pump up to the VSV's (drivers side fire wall) are intact. Make sure that when you removed the emissions stuff the vacuum line that went to the other side of the engine bay was actually blocked off properly. There is a high chance this is what the problem is.

 

[digitalbuck]

Here is an update for anyone having a similar problem with their electric hubs. With all of the reading I did online I never came across anyone dedscribing this exact situation:

I was getting a loud ratcheting sound when I tried to engage 4WD, either in high or low. I checked vacuum and actuators and everything was working but I still got no action to the front wheels and had this loud ratcheting sound whenever I tried to engage it. The sound would not go away until I disengaged or stopped moving.

I took the cover off of the hub and saw that the motor to lock the hub was in fact turning as it should. Then I inspected the outer portion of the hub and saw that the hub was not rotating to push inward. It was just stuck from lack of use. I freed it up, got it working well, and put it back together. Now everything is functioning as it should. The teeth on the hub were just pushing in far enough to rub against each other lightly, making the loud ratcheting sound, but not enough to engage.

I hope that helps someone else!

 

[Gun Runner 5]

I hope yours continue to work however that motor has gears that are better suited to a cheap watch than a 4 wheel system.

 

[digitalbuck]

I hope yours continue to work however that motor has gears that are better suited to a cheap watch than a 4 wheel system.

Well I hope so too! But I'm planning on converting to manuals. This was just a temp fix that restored my 4WD function.

 

[Gun Runner 5]

We canalbalized one of the small motors and was shocked to see how SMALL the gears were. It's amazing they produce enough torque to engage anything. I'm hoping to modify my OEM electric hubs where they can be locked manually.

 

[GTSSportCoupe]

We canalbalized one of the small motors and was shocked to see how SMALL the gears were. It's amazing they produce enough torque to engage anything. I'm hoping to modify my OEM electric hubs where they can be locked manually.

Ever opened up a cordless drill? Same thing, tiny gears, but it's amazing how much torque they can produce. It is that gear ratio in fact that makes the torque.

I think if the e-hubs are maintained properly they can be perfectly reliable. It's just that no one maintains them. And many break the brushes while servicing other things like hubs or brakes. When working on mine I did not get the feeling the e-hubs are cheap, just that they are too delicate/complex given the application. Manual hubs are the way to go for most. For myself, I like pushing the hub button, having a sip of coffee, while all the other guys get out of their trucks to manually engage their hubs (on our local 4x4 trips).

 

[AirheadNut]

I once had a similar problem: on a bit of an axle twister after engaging 4wd I noticed that the front wheels weren't doing anything, and when I backed up I could hear the ratcheting sound, albeit faintly. I slowly moved the vehicle forward and backward and the hub engaged.

 

[Gun Runner 5]

In case you've never seen the inside of one of the motors.

 

[Gun Runner 5]

The shops working on a mod for my Cruiser that will only use the one gear (below the quarter) and will allow manual activation of the hubs while maintaining the OEM look.

 

[JuanJ]

Ever opened up a cordless drill? Same thing, tiny gears, but it's amazing how much torque they can produce. It is that gear ratio in fact that makes the torque.

I think if the e-hubs are maintained properly they can be perfectly reliable. It's just that no one maintains them. And many break the brushes while servicing other things like hubs or brakes. When working on mine I did not get the feeling the e-hubs are cheap, just that they are too delicate/complex given the application. Manual hubs are the way to go for most. For myself, I like pushing the hub button, having a sip of coffee, while all the other guys get out of their trucks to manually engage their hubs (on our local 4x4 trips).

Hello,

I guess the engineers who designed the electric hubs assumed two things:

1. Users would maintain them properly.
2. Front axles having them would not spend much time in deep mud/water/sand.

None of the above describes typical Land Cruiser operation. No wonder they tend to fail over time.







Juan