Clunk when switching from 4WD to 2WD with tension on the driveline

I have a 2019 TRD Off Road. Manual transmission, just turned 2000 miles. I was in 4WD Low for the first time with this new truck in a field. After getting back on the road, I switched out of 4Low and into 4High, but ultimately wanted to choose 2WD. By the time I got around to switching into 2WD, there was already a slight bend in the paved road. The truck clunked out of 4WD and into 2WD.
I’m trying to be super careful with this new and expensive vehicle, so how concerned should I be over an incident like this? Thank you.

 

None. It happens.

Just left off the gas and coast when you shift and it won’t clunk.

 

Were you stopped or barely rolling when you switched from 4L to 4H?

Mines made a few “clunks” the first time I used it in the snow (4H to 2WD) but from what I hear it’s pretty normal. I’ve found the best way to switch now is to let my foot off the gas, change the switch, let it coast another second and then slowly add gas again. Breezy

 

It is best to switch between the 4WD modes with no tension on the driveline if possible. Flat ground and to a rolling stop.

No harm done if this can’t be achieved.

 

^^^^ All of this.

 

I have a manual transmission and was in Nuetral for all of this process, but was making a medium sized turn to the left.

 

My auto does it too if my wheels aren't straight - too much stress on the transfer case if in the middle of a turn. Nothing to be concerned about damage though. Just don't make it a habit. These trucks are pretty tough.

 

Normal as stated, I believe the clunk comes from the Automatic Differential Disconnect (ADD) fork. That mechanism shifts best with no tension on the driveline.

My first clunk experience was actually when parked. I turned the knob, and the light flashed began flashing. I was probably fiddling with the radio or something, not paying much attention. Suddenly there was a firm *clunk* and the light was off. The wheels never really moved, but there was just enough tension on the driveline to keep that ADD fork from releasing. Therefore, best to shift at a slow roll to keep that bind up from happening.

 

So, does it harm anything? I won’t be making a habit of it, but what exactly is making the clunk noise and can it hold up to an occasional imperfect shift in and out of 4WD?

 

Thank you! I think I can sleep at night now! I really try to keep this truck in awesome shape. It was a bummer to hear a loud clunk. Thanks again for the information.

 

Simply the very best educator on the ol’ YouTube.

If you watch this whole video, it will serve you well. Video is of Tundra, but Tacoma is identical principles with slightly smaller parts.

All clunks will become obvious.

https://m.youtube.com/watch?v=47m7QAPrpsI

 

It's good to know how this system works. Two key components in the shift process are the transfer case and ADD. If you ever notice the light blinks constantly during a shift (usually happens when shifting at a stop), it is usually because the ADD isn't able to spline onto the front differential collar. Once tension is released or the gears move, everything lines up.

 

My 2002 1st Gen was horrific sounding going back and forth between 2WD and 4WD super loud and I could feel the whole driveline moving, even while stopped.

Really wouldn’t worry about anything unless something breaks or stops working. Trucks make a lot of noise, especially 4WD and leaf suspension.

 

Thanks @TacoMamba35 ! I just used 4LO on my new truck for the first time and got so confused when I was trying to return it to 2HI when I was bringing it into the garage. The 4HI light was blinking and I couldn't figure out what was going on, I was in neutral with the clutch in and it did give a little lurch eventually when I moved the car a bit. Would you recommend getting a little speed before switching in & out of 4wd? I have my accessories appointment tomorrow so maybe I'll ask the dealer as well

 

4hi <=> 2hi is smoothest when moving in a straight line, especially on a low traction surface. 4lo <=> 4hi requires a full stop with no strain on the drivetrain, best done on a low traction surface.

A low traction surface does not include wet pavement. I’m talking about dirt, grass, gravel, sand, mud, snow, or ice.

 

Thanks @gudujarlson ! Will be testing it out in a few mins. We got freezing rain overnight and I have an appointment this morning to grab some winter tires.

 

It is really bad when you are turning and pulling a trailer. First time it happened to me, I thought I hit something. Scared the shit out of me! Lesson learned lol.

 

the clunk is normal, through the life of the truck you will need to engage and disengage in the middle of turns at times. Its best to have your wheels lined up straight before engaging and disengaging; keep that in mind when looking up the road wondering if you should 4 wheel it or not.

 

Normal, just do it going in a straight line and not under load. Best stopped in neutral and without brake on

 

Just pulled this dumbassed maneuverer this morning. Lesson learned and glad I didn't jack anything up. Thank you for the information and putting my mine at ease. New to 4WD so lots to learn!