4WD (H4) not working. Help!

I apologize in advance if I overlooked the same exact thread but I need help please. I have a 2009 Tacoma 4WD, 6cyl, 6 speed manual. When switching to H4, nothing happens. I hear no noises, and no lights illuminate on my dash. When I switch to L4, I hear noises and the 4WD light and "Lo" light illuminate on the dash along with beeps and I can feel the change. Can you guys, in your infinite wisdom help me? I am slightly mechanically blessed but not a mechanic. Any info is much appreciated.

 

Are you driving while turning the switch?

The beeping means it won't go into 4 low because you are moving or the gears aren't lined up in the t case - or you aren't in 4wd.

The truck should be rolling to shift in and out of 4x4. There are well known problems with the t case actuator (can usually be solved by soldering the connections) and also the ADD failing. Both can be switched in manually if you REALLY need to be in 4x4. Look up transfer case trouble shooting and also ADD trouble shooting.

 

Suddenly, my 4WH and 4WL work just fine!!

 

If you had a problem with it once, it'll probably happen again. I had to replace the actuator on the transfer case, which is responsible for transferring power to the front axle, AND the front ADD actuator, which is responsible for locking the front differential.

How I came to understand the system is this:
4WD switch -> ECU (Electronic Control Unit, behind the glove box) -> Transfer case -> ECU -> ADD actuator.

If you were able to get into 4LO, but not 4hi, I would suspect your transfer case actuator since the front differential is either locked or unlocked, where as the transfer case has 3 positions, 2HI, 4HI, and 4LO. Perhaps it was having some problem receiving the signal/delivering power to lock your transfer case to the 4HI position.

I'm not a mechanic, I just spent a lot of time thinking about it and eventually determined I needed to replace the actuators and now everything is gucci.

Hope this helps if it happens again.

 

This is slightly incorrect. The front differential is never “locked” unless you’ve installed an aftermarket locker in the front Diff.

In the front, it’s the ADD actuator sliding the stub shaft over to apply power from the front differential to the passenger side axle.

I know what you meant, but the above is how it actually works

 

And OP, there are threads upon threads on this issue. I’m sure you can find all
the info you need here.

 

Word, thanks. This makes sense.

 

Most likely operator error and it sounds like you've figured it out. Shift into 4hi from 2hi while moving. It takes a second or 2 for everything to engage. Shift from 4hi to 2hi same way. If you're completely stopped it may engage, it may not engage until your wheels roll a partial turn.

If going to 4lo shift into 4hi first, then stop the truck, place transmission in park or neutral with an auto. With a manual you can depress the clutch. Then shift into 4lo. Once again, you may have to let the wheels turn a partial turn before it engages. It helps if you are rolling very slightly instead of a dead stop.

Getting out of 4lo can be tricky. Sometimes the gears just don't want to disengage. Don't try to go straight from 4lo to 2hi. I find it best to go back to 4hi first. At times you may have to back up 10'-20', then move forward some in order for the transfer case to disengage from low range. I've had to repeat this dance several times in the past. Once in 4hi drive away and shift back to 2hi ASAP.