Loud thunk when trying to engage 4wd

Howdy all. so I have a question on the 4wd on the 2nd gen. last Wednesday we had a snow storm so I thought I’d use my 4wd and when I did, it never engaged so I turned it off and when it finally stopped blinking, it thunked really hard as if I went through a large pothole. Tried it a couple more times and same thing. Took it to Toyota, they never found anything wrong, but I serviced the 4x4. After i got it back, I tried it again. And same thing. No engagement, and loud hard thunk. They say I’m doing it wrong and want to drive with me and watch me engage it. Every time I’ve tried I was going 20-40mph on straight roads. (Never turned) any help would be awesome. Thanks in advance!

 

you might want to be stopped to engage it, not saying you cant engage it going 40mph but having moving parts catch non moving parts at that speed isn't the best thing.

 

Is it doing the same thing when you try to engage at a standstill?

 

I’ll try when I get home but I’m more worried about the hard loud clunk sound from when i turn it back to 2wd

 

If there's gear oil in your diffs then maybe its binded up and you're turning your wheels too soon....

I would recommend sitting in park, engage 4wd, and then shift into D. Then slowly roll forward and it should be engaged.

 

When you try and engage/disengage, are you lifting your foot off of the gas? I get a thunk about half of the time when disengaging.

Also how are you sure it's not engaging? Light just keeps blinking?

 

These trucks prefer to engage 4wd while moving. Maybe try it slower for testing purposes, like 5-10 mph.

 

Is this at speed also?

Any specific guidance on operation in your owners manual?

Do you exercise the 4wd monthly (regardless of weather) as recommended in the manual?

 

Mine thunks at a standstill but engages/disengages fine. If it's thunking and not engaging I'm guessing the front driveline is engaging and disengaging but the front diff isn't engaging. Just a guess though.

 

For 4H I always engage at like 5mph or less, I believe in 4L you have to be stopped and in neutral but I could be wrong as i've never needed to use my 4L.

 

Wouldn't try shifting it at 20 or 40mph., not to say it can't be done, just not a good idea. For me stopped or barely moving with front wheels as straight as possible. I'd think a clunk would be gears almost engaged then popped back out. Good luck

 

I also try to never have my foot on the gas when I go to 4HI. If you're racing the engine it'll clunk when you switch.

 

There's nothing wrong with shifting at speed as long as you're under 55 or whatever it says in the manual. Have shifted in/out of 4hi plenty of times going 40mph with no issue, yes sometimes there is a clunk but that happens at 5mph and even at a stand still sometimes as well. Never been an issue.

What you do want to watch out for at speed is tire slippage...never shift into 4wd when the tires are slipping, that can cause damage for sure. I always let off the gas when shifting in/out of 4wd at any speed to prevent tire slipping.

Clunk is normal, every Tacoma does it. If you search 4wd clunk on the forum you'll see a bunch of people say the same thing.

 

Thanks for this post, hard to believe everyone here has the opportunity to stop when they want to switch to 4wd. I've engaged and disengaged it driving quite a bit, and I only hear the clunk when I am disengaging at a stand still. It's just the actuator moving parts around.

In this case I think the clunk could mean that the transfer case is being actuated, but that the 4WD isn't engaging because of a problem with the Automatic Disconnecting Differential aka ADD. If possible, activate 4WD and see if the front driveline spins when you move. Maybe you can mark it with paint and drive a couple feet and see if it is in the same position.

(4LO is a different beast and I engage it at a stand still in Neutral personally)

 

Just try to keep aware of your surroundings, If you are going 40 mph & then suddenly realize you need your Taco in 4X4, In my opinion, you're already late, should have hit 4X4 before you got into that situation. Also, & again just my opinion, If the roads are bad enough you need to be in 4X4 to keep going, I wouldn't be driving 40 mph. Yes, you can go that fast, 4X4 will get you up to that speed but it does little for stopping you. Either shifting into 4X4 at 40 mph., or driving 40 mph. on a road slick enough to need 4X4 is fine for those who want to do it, just doesn't seem like the best of ideas. Good luck to everyone.

 

Foot off of the gas when engaging, and be sure to exercise regularly.....

 

Yeah, nothing wrong with shifting while moving or standing still, but the pressure on the drive line from being on the gas will make it difficult to go into 4WD and create a thud when coming out.
Every 4WD vehicle I've driven from Toyota, Ford, Dodge, Chevy, and AM General does the same.

 

I get a good thunk every once in a while. Whats worked for me the best is when moving, move to neutral, let rpms die to idle, and then switch to 4 hi. usually in the 20-40 mph range, Almost eliminated the noise for me. That said, i still shift at times without doing all that. 4 Lo, i use neutral, not moving.
If you really got to work at getting to shift in, stop, shift to reverse and move a couple feet, then forward same thing. Eventually it catches.

 

I get the same “clunk” in winter using 4WD for the first time. It’s been doing this since day one in 11 yrs. of ownership. Exercising it weekly throughout the year will probably do away with the clunk, but I never remember in the warmer months. I usually put in 4WD at a slow roll.

 

If you're at a dead stop you have about 50/50 odds that the gears are lined up properly for 4X4 to engage. When you start moving from a stop after you engage 4X4 the gears will mesh when things line up, you only have to move a few inches. Hearing a noise would be normal. It is best to engage 4X4 when moving slowly, under 5 mph. It also helps to take your foot off the gas pedal for a few seconds after you flip the switch. If the transmission is under load as you accelerate it often won't shift until the stress is off. And then it will shift harder and more likely to make a thunking sound.

If it is safe enough to be driving 40 mph you have no business in 4X4. If you need 4x4 it isn't save to be driving over 10-20 mph.

If you have a 4X4 you need to engage 4X4 and drive a few miles in 4X4 on a regular basis. 10 miles/month is the recommended amount. I don't always get 10 miles each and every month. I may skip a month, but I won't skip 2. And while I may not get in 10 miles every month, other months I may get in more than 100. This keeps internal parts lubricated and helps prevent corrosion in electrical connections. The key is to use it, or you'll lose it. This is as important as changing the oil regularly. Do this and you won't have problems when you need it.