I got snow for the first time in a while, so I'm getting a lot of use out of my 4wd. I've noticed that when I go into 4wd, I hear a lot of clicking before the light goes on.

Sounds like a relay, but I think it's part of the vacuum system. Anyway, one click is normal, but now that it's cold it has to try 5 or 6 times before 4wd finally engages. Once 4wd is on, everything works as it should and going back into 2wd works perfectly fine.

Is my 4wd about to fail? Why does it appear to be struggling to get into 4wd? What exactly does this clicking sound come from?


I've had problems with my 4wd before, once it completely let me down but the problem resolved itself after a week. Funnily enough both times it was 12 degrees out. Ever since then I've exercised 4wd at least once a month.

Check the Vacuum lines running from the VSV down to the Frt Diff. You might try pinpointing where the clicking is coming from. I would guess your problem is a cracking vacuum line or failing VSV.

hello, mine is jshifter but totally manual.
im having no experience/knowledge about yours but since its working then its fine but struggling to do its job
maybe a vaccum or the front diff actuator starting to get stuck, my approach is to try cheap/easy thing first to eliminate as much possible things to look at,, you may change the front diff fluid with fully synthetic 75w or 75w-90 or what you technically preferring.
also trace yourself all vaccum lines or do smoke test, or grabe a vape and blow smoke to verify any crack in the lines.

since issue appeared these days during cold temps i would suspect the actuator struggling to do its function due to sludge

I personally only seen one of mine do this. The lines etc were all good it just all thr sudden didn't lock in the front diff. I ended up changing the add relays and everything worked perfectly again. Granted this rig was a mug bugger before it came to me so I expected they just wore them out or damaged them somehow.

Mostly the ADD system is very solid. So if it's not the vacuum libed or the shifting fork. Check the relays ..

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My front diff fluid was changed little over 10k miles ago with full synthetic.

When I had similar issues years ago my best guess was the hoses because they looked dodgy and are covered in oil from a leaky oil pan gasket. Don't remember all the clicking though.

Assuming OP is right about the ADD relay location in this thread, the clicking I'm hearing appears to be coming from it.

The fact that the relay switches on and off until it successfully gets into 4wd makes me wonder if Toyota programmed it to keep trying until it sensed it successfully switched into 4wd. I'll have to check my fsm.

If it was a bad vacuum tube wouldn't it have problems getting out of 4wd as well as in?

Two possible issues -

4WD switch on the transfer case or ADD relay.

If the 4WD switch is sending a weak/bad ground to the ADD relay, the relay may click multiple times. If the ADD relay is going bad, it could click multiple times.

The j-shifter system isn't 'smart' enough to re-try things - it is either ON or OFF. So, something 'mechanical' is intermittent in the switch/relay part of the system.

-Charlie

Yeah, the issue is clearly electric. There is no way anything in the lines could cause that ADD relay to do that clicking thing I know so well. (Relay is in the right kick panel, up high on the firewall extreme right.) It's the wiring or the switch is my bet. A failing relay rarely does the clicking thing. it's the input to the relay nine times out of ten.

I gave up on those silly switches, and wired a simple switch from the dash to the ADD relay, so I can control when the ADD engages with 100% confidence. I think I was on my third switch. I assume the salt here kills them.

The rig us just sending you sos Morris code in your relays to the ADD.

Makes since a wire or switch is going bad.

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Are your tires mismatched or worn uneven left to right and there is a speed difference between the two wheels causing the collar to overrun?


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My tires are decent, I rotate them following the suggested interval. I bought all 4 tires at the same time, and I never had mismatched tires on the vehicle.

There is the slightest uneven wear, but it's so minor I had to use a tool. Not enough to matter.