Mysterious 4wd problem

My 4wd recently stopped working properly: specifically, if I switch to 4hi, it engages 4wd, but the 4wd indicator light keeps blinking. When I switch back to 2hi, the stays in 4wd (but with the light blinking) until I restart the truck.

So I unplugged the 4wd actuator at the differential, and plugged in new OEM actuator without installing it in the differential. I switched to 4hi and the actuator fork moved, and the indicator light came on without blinking as it should. I switched back to 2hi, and the indicator light turned off. Problem solved, right?

So I installed the new actuator in the differential, and the problem persists. The truck engages 4wd but the light blinks, and when I switch back to 2hi the truck stays in 4wd (but with the light blinking) until I restart. When I restart, there is a big clunk as the truck switches to 2hi.

I suspect both actuators work outside of the differential, but not installed in the differential. (I’m going to test the old actuator tomorrow to confirm.)

What’s going on?

 

Are you moving when shifting? You’re supposed to be moving for a 4Hi shift. If the splines aren’t lined up, then it isn’t going to shift until they are lined up, and they won’t line up until you’re moving and line them up.

 

When you switch to 4Hi, are you doing it while stopped or while the vehicle is moving? If you're switching while stopped, and then put the truck in drive and let it move forward, does the blinking stop and the 4Hi light stay solid? If you're switching to 4Hi while the vehicle is moving, what's your speed? Keep in mind you need to be under 60 mph when switching to 4Hi. Have you also checked the transfer case actuator? It contains a small motor, and some people report issues with bad solder joints or faulty contact points. This might be something worth inspecting.

https://www.tacomaworld.com/threads...w-to-manually-shift-the-transfer-case.703240/
https://www.tacomaworld.com/threads/2008-transfer-case-actuator-update.696251/
https://www.tacomaworld.com/threads/4wd-system-help-and-information.696298/
https://www.youtube.com/watch?v=1Po9iYu16N4

 

5mph

 

Turning at all?

 

Sounds like when the actuator is installed something is preventing it from going through the full range of motion so the computer doesn't know if 4hi is engaged or not. It works fine when not installed so it's not the main t case or a wiring issue (unless when installed the connector is being stressed somehow?) You're going to need 800' of good quality synthetic rope and 15 pulleys (sorry, wrong thread couldn't help myself ) Try removing the actuator and manually sliding the collar inside the diff - see if there is any resistance at the far end of its range. If you don't use 4x4 often it could just be a buildup of gunk or something. Make sure you note the position it was in before you touch it and put it back there before you replace the actuator. Regarding the clunk when you turn the truck off and back on, it's probably just because you're not moving when you turn it back on but because you have 2hi selected it shifts immediately - try leaving it in 4hi when you turn it off and see if it flashes when you turn it back on. If not, shift when moving as you would normally do.

 

The slide collar seemed to move freely with the actuator off but I don’t have another one to compare to know whether it moves the whole range. Seems like it does.

I use 4x4 regularly and I changed the diff fluid a few hundred miles ago.

 

It would seem like something in the front diff is preventing the ADD Actuator from moving fully to the locked position per your testing.

You can check your limit switch voltages to see if that's the case, if it is I would expect all of them to be correct except ADD.

https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

To be in 4X4 two things have to happen. The transfer case has to engage, and your hubs have to lock. I've seen grease in the hubs harden and prevent the hubs from locking. No parts needed replacing, just clean and re-lube the hubs. I've seen this happen with manual and auto-locking hubs.

 

No locking hubs in the 2G though - front axles are always spinning, 4x4 is engaged at the t case and diff

 

Differential was regeared/rebuilt 5,000 miles ago. It does have an autolocker, which I’ve had for perhaps 20K miles.

 

I don’t have a multimeter, unfortunately.

 

Okay, here’s a twist: The truck can switch from 2wd into 4wd even without the installed ADD being connected to the wiring harness. (To clarify, I plug the harness into an actuator this is not installed on the differential to let the truck think the ADD is doing something.)

I put it up on jack stands to verify because I couldn’t believe it.

 

I thought you already determined this by watching it work off of the truck earlier on?

 

No, I’m saying *the front wheels start turning* when I switch to 4wd, even though the actuator that is currently installed on the differential is not plugged into the harness.

What I had verified before is that both actuators work, by watching the forks move while they were plugged into the harness but not installed in the differential.

 

Then the ADD that is installed is in the locked position.

 

X It’s not though.X Edit: Yes it is.

I can’t verify this because the differential is all sealed up, but it was in the 2wd position when I put it back together, unless I’m losing my mind.

Edit: You are right! The truck’s computer does not think the ADD is locked, but when I turn the front tires in the air the front drive shaft spins.

 

Well it has to be or it's installed improperly because the axle is locked in you said.

 

I edited the post you quoted. It is locked. The truck’s computer does not think it is, but I spun the front tires in the air in “2wd”, and the front drive shaft spun.

I’m not sure if something slipped during the install or something is preventing it from fully decoupling after 4wd is engaged, but I’m going to pull the front ADD, actuate it outside the differential and verify the fork is as far toward 2wd as it can go, and put things back together.

It’s a new OEM actuator that I verified it was working before install.

 

Thank you for your link to your excellent and informative post. After reading some of it, I decided to buy a multimeter.

In testing 4H, some of values that should be “12” vary, from 11.67-12.25. Is that an acceptable range? Also, one of the values that should be “0” reads 0.01.

Edit: of note, I don’t have real back probes. I am using a sewing needle taped to the terminal.