Loss of 4WD after it is engaged

[FrontRange4Runner]

2 days ago I was driving around, finally getting to use my 4wd in the snow. Road conditions were wet to snow packed. Ambient temp was right around 30F. I was driving up to a light, roads were only wet here so I took her out of 4WD. As I was slowing to the light, there was a definite thump felt through the drive terrain (I tried to ignore it, but the old test driver in me could not stop thinking WTF). When I stopped, the 4WD indicator flashed for 20 seconds and then went off. A few miles down the road I was back on snow pack so I engaged 4WD and continued. It took immediately, gauges were green and all was well. About a mile later, the indicator began flashing, and continued to flash even after disengaging. I was able to to get it to stop by putting it back in 4wd, and driving slowly. After that it seemed to work normally for the rest of the night. Anyone ever have this happen before? Generally speaking, 4WD will not disengage it's self...I did some reading in the manual, however nothing I found seemed to provide any answers. Just seems a bit strange....

 

[mo_mo]

I know that if I switch out of 4x4 while on the gas then the ADD won't disconnect and the light will flash. I have to ease off the gas to unload the drivetrain then it will disengage. I would expect similar behavior if switching while braking.

Not sure about the flashing after it seemed to engage properly.

 

[flyinhawaiian01]

It also helps to turn the wheel slightly left and right of center to make sure the front diff isn't bound up a bit.

And clunking when it comes out is quite normal, that tells me your axles were slightly bound up when you took it out of 4wd. Also, the vehicle needs to be rolling slightly for it to go in or come out of 4wd, I think it also says that in the manual, but I haven't bothered to read it, I've had ADD Toyotas for the past 20+ years now and am just used to that bump feeling from the drivetrain!

 

[ic0517]

I was under the impression if you can see you are going to be driving in a straight line between the slippery patches, you can leave it in 4WD. I'm sure I will be corrected if I am wrong.

Learned somewhere on this forum that there are two changing parts to the 4WD. The transfer case is underneath the lever in the cab, but there is also something out there that 'locks the hubs', if you have ever seen an old Ford F150 4WD with the red or pink knob in the center of the wheel, that. And I will admit I don't know where it is, that is a decent weather kind of thing, go crawling underneath and look. Sure somebody knows where it is and has a picture of it.

Beauty of a 4Runner is you don't need to jack it up to take a look unless you are like me and had too many Italian beefs.

 

[4Rager]

2 days ago I was driving around, finally getting to use my 4wd in the snow. Road conditions were wet to snow packed. Ambient temp was right around 30F. I was driving up to a light, roads were only wet here so I took her out of 4WD. As I was slowing to the light, there was a definite thump felt through the drive terrain (I tried to ignore it, but the old test driver in me could not stop thinking WTF). When I stopped, the 4WD indicator flashed for 20 seconds and then went off. A few miles down the road I was back on snow pack so I engaged 4WD and continued. It took immediately, gauges were green and all was well. About a mile later, the indicator began flashing, and continued to flash even after disengaging. I was able to to get it to stop by putting it back in 4wd, and driving slowly. After that it seemed to work normally for the rest of the night. Anyone ever have this happen before? Generally speaking, 4WD will not disengage it's self...I did some reading in the manual, however nothing I found seemed to provide any answers. Just seems a bit strange....

I was driving to meeting in the snow this morning and I noticed the same thing, minus the clunking. The freeway had minor snow, so on the way there I was in 4wd. On the way home it was pretty much clear, so I shifted it back to 2wd. I had traveled about a 1/4 mi and noticed the 4wd indicator was still lit. I was still lightly pressing the gas, but as soon as I left off it switched back to 2wd. As other suggested, it seems the drive train will not make the switch while under load.

 

[rigtec]

It occurs to me that there's more going on here than just 4WD being engaged e.g., ABS, A-TRAC, VSC... all working together to maintain vehicle safety! If this is the first time that you're using the 4wd feature on a slippery road surface, you will encounter flashing notification icons from the instrument cluster from time to time. I know that there are guys here that know farrrrr more than I know about this subject so I hope they'll chime in to provide more clarity! In the mean time, I'm leaving a couple of Toyota traction system vids to help show how these systems work... there are a lot more videos on the subject on these same pgs,

https://youtu.be/rYB3b4_UFlA

https://youtu.be/A2eyBCX0ZWQ

https://youtu.be/KxiVNfwMp7A

https://youtu.be/Yy990IvRlGY

...And this one's just fun to watch lol!:

https://youtu.be/T8onFpQY6tE "Enjoy!"

Cheers!

 

[sooperedd]

I have only had mine in 4WD a couple of times since buying it in June but I also noticed when I switched out of 4WD the light would stay flashing for almost a minute after.

I just figured it was normal.

 

[BobsTrail]

I was in 4wd. On the way home it was pretty much clear, so I shifted it back to 2wd. I had traveled about a 1/4 mi and noticed the 4wd indicator was still lit. I was still lightly pressing the gas, but as soon as I left off it switched back to 2wd. As other suggested, it seems the drive train will not make the switch while under load.

I think it's a "Trail" thing with the lever. Mine does that also, when I shift back to 2WD the lever gives some resistance as though it's binding. Letting off, coasting or going into neutral cures it. If I'm coasting it's OK and does a quick disconnect. When it works OK the lever feels like a manual gear shift, no resistance.

I have experienced this a few times in the driveway and garage while screwing around putting it in and out of 4WD.

 

[rigtec]

My limited does the same thing, not with the 4wd as I only have Full time 4wd. But after switching in or out of HI or Low lock, I'll need to roll a few feet to either engage or disengage the T/C. Once I do that, the 4-HL or 4-LL light goes out. Best!

 

[adam2562]

normal.. i just let off the gas or get on the gas to un-bind or reduce pressure on the drivetrain and that's usually when it shifts in or out 4wd

 

[wfo9]

This is the ADD actuator trying to disengage the passenger side axle shaft. It can't do it under load as things are in a bind.

Always take your foot off the gas when going in and out of 4wd to keep things smooth. Slight turns from side to side can also sometimes help.

On trails and older sr5s with a manual shifter the transfer case is engaged manually. So once the shifter is in the correct position the front drive shaft is seeing power, but you don't actually get power at the front wheels until the ADD can engage the passenger side axle. Until then it acts just like passenger wheel was up in the air.

Similar thing happens when shifting to 2H with a shifter. Front drive shaft stops getting power immediately, but the ADD needs to release the passenger side axle shaft to stop the drive-shaft from seeing motion. Models with the knob, need to also actuate the transfer case in a similar manner and load will stop it from happening immediately.

 

[flyinhawaiian01]

That's a perfect, detailed description, WFO9! :bigok:

 

[FrontRange4Runner]

*I did a terrible job of explaining what actually happened (but learned something from this thread anyways..awesome!) The top 2/3's of my original post was simply what I was doing before my actual problem. My problem was as follows: Driving in 4WD, for over a minute - the indicator was solid green. Then, out of nowhere, while driving straight at 25 mph, it started to flash. It continued to flash even after taking it out of 4WD (for at least 100 yards) and re-engaging it. I have never seen it drop 4WD before (obv the lever did not move), and I have no idea what would cause this. Any Ideas?

 

[mo_mo]

*I did a terrible job of explaining what actually happened (but learned something from this thread anyways..awesome!) The top 2/3's of my original post was simply what I was doing before my actual problem. My problem was as follows: Driving in 4WD, for over a minute - the indicator was solid green. Then, out of nowhere, while driving straight at 25 mph, it started to flash. It continued to flash even after taking it out of 4WD (for at least 100 yards) and re-engaging it. I have never seen it drop 4WD before (obv the lever did not move), and I have no idea what would cause this. Any Ideas?

I think you have the lever actuated 4x4 system. Are you sure the lever was fully seated and didn't get jostled away from the end stop...which might not fully engage the limit switches and would tell the system to disengage the ADD? Can you replicate the problem?

 

[FrontRange4Runner]

I think you have the lever actuated 4x4 system. Are you sure the lever was fully seated and didn't get jostled away from the end stop...which might not fully engage the limit switches and would tell the system to disengage the ADD? Can you replicate the problem?

I do have the lever system. It was fully locked into position at the time of the issue. I attempted to get it to happen a bunch more over the last few days but have been unsuccessful. Hoping it was simply a fluke and will not come back. It does not look like this has happened to anyone else around here so that is probably a good thing!

 

[Ron4RNevada]

The advantage of the knob shifter - - - -

 

[wfo9]

I do have the lever system. It was fully locked into position at the time of the issue. I attempted to get it to happen a bunch more over the last few days but have been unsuccessful. Hoping it was simply a fluke and will not come back. It does not look like this has happened to anyone else around here so that is probably a good thing!

There is a sensor on the top of the t-case, that detects when the t-case is shifted to 4wd. The 4wd ECU uses this to trigger the ADD... This sensor can go bad and there was a recent post on here about one that did. In his case, it would simply not engage the ADD at all, but I could see that same sensor being intermittent.

I would just keep an eye on it... If you put all the wheels in the air.. you can quickly determine if the T-Case, ADD, or both are engaged.