Need help diagnosing a 'clunk'...

#1
I've had this clunk for a while now, and figure it's time to find the culprit.

The sound is from the front end, and I don't "feel" it through either the pedals, floor, steering wheel, or anything else I may be in contact with.

It happens in two scenarios:
1. decelerating to a near-stop, then letting go of the brakes *clunk*
2. backing up into my parking stall, riding the brakes, turning the wheel left/right *clunk*

The clunk generally doesn't happen in normal driving.

I had the truck serviced yesterday and asked the dealership to look at it... they "took a wrench to all bolts" and told me I have aftermarket suspension. Would have happily paid them to diagnose the problem, but I guess they weren't interested. Still clunking.

So... 2016 Tacoma TRD Sport 4x4 with the following changes in the front end:
- ICON upper control arms, 2.5 shocks w/ remote reservoirs, swaybar relocation/spacer (came with the suspension)
- Mobtown skid plates (front, transmission, t-case)

The parts have all been on the truck for a long time, and the clunk only started happening in the last few months. There have been no changes to anything in the front end near/around the time the clunk started happening.

There are no leaks or other clearly visible problems that I can spot.

I'm fairly certain the rotors are warped (brought this up w/ the dealer, but they couldn't confirm without doing a full on brake job... lol), and they told me the brakes are at 30% all around. Not sure whether lower pad thickness could result in some clunking issue w/ the calliper's piston movement? Probably not, but who knows...

Any ideas of what I could look at or try?
 
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DaveInDenver

Expedition Leader
#2
I have something similar perhaps, but is this your first Tacoma? I ask because they seem to develop a clunk in the rear driveshaft that is usually a TSB or warranty item related to the u-joints and center support bearing. I'd check that first, grease the Zerk fittings if yours is equipped and check for play in the carrier bearing.

But otherwise make sure your tie rod ends, ball joint(s) and alignment cams are all tight.

Oh, almost forgot, another source of a front end clunk on Tacomas are the brake pads. At least on the 2nd gen Toyota only installed one return spring between them and as they wear, particularly the pin, they'll sometimes grab and clunk. When I did the brakes recently I put two in like my old 1991 had. You may feel this in the brake pedal, though.

Assuming that stuff checks out, another source that I'm trying to nail down is the upper arms. I noticed once that I had a clunk and it seemed to stop for a short time after I greased the bushings. I have Camburg UCAs, which are similar to your ICON (although I have ball joint versions, not uniball). I haven't had the urge to deal with the cold this winter to test my theory a second time but I'm getting a slight clunk again.
 
#3
Mine does that when it has been sitting undriven for a few months. It's evidently pretty common. Google Toyota Tacoma drive line clunk.
 
#4
I have something similar perhaps, but is this your first Tacoma? I ask because they seem to develop a clunk in the rear driveshaft that is usually a TSB or warranty item related to the u-joints and center support bearing. I'd check that first, grease the Zerk fittings if yours is equipped and check for play in the carrier bearing.

But otherwise make sure your tie rod ends, ball joint(s) and alignment cams are all tight.

Oh, almost forgot, another source of a front end clunk on Tacomas are the brake pads. At least on the 2nd gen Toyota only installed one return spring between them and as they wear, particularly the pin, they'll sometimes grab and clunk. When I did the brakes recently I put two in like my old 1991 had. You may feel this in the brake pedal, though.

Assuming that stuff checks out, another source that I'm trying to nail down is the upper arms. I noticed once that I had a clunk and it seemed to stop for a short time after I greased the bushings. I have Camburg UCAs, which are similar to your ICON (although I have ball joint versions, not uniball). I haven't had the urge to deal with the cold this winter to test my theory a second time but I'm getting a slight clunk again.
Yes, first Tacoma, and first truck, actually.

The dealership told me they'd grease the zerks, but I didn't verify that they actually did that. I guess that's the first step.

A friend of mine is a mechanic at Toyota and he also suggested brake pads as the culprit when I brought this up to him (he didn't see/drive the truck, though).

UCAs are something I thought of, but then I'd still have this clunk while driving, and I don't. Mine need a good greasing regardless, though.

Thanks for the help!

Mine does that when it has been sitting undriven for a few months. It's evidently pretty common. Google Toyota Tacoma drive line clunk.
Thanks for the tip. Just read about that issue and while it makes sense as the potential culprit for the clunk I hear when I slow down and then release the brakes, I don't think it makes sense for why I'm hearing the same clunk when backing up. When reversing, the speed is incredibly slow, so I don't think the rear diff's pinion angle would increase much (if at all).
 

DaveInDenver

Expedition Leader
#5
YUCAs are something I thought of, but then I'd still have this clunk while driving, and I don't. Mine need a good greasing regardless, though.
I didn't clarify, my UCAs seem to have a clunk and I only hear it with the wheels turned in parking lots or pulling into my driveway over a curb. I don't hear a clunk normally. My theory is it's got to do with the polyurethane bushings grabbing slightly or perhaps a bit of misalignment in the arms relative to the frame mount. Which is why a liberal coating of grease made it go away for a while I think. Hey, it's not a fully developed theory, just a working one.

I know it's not wheel bearings, those are brand new.

I did have the brake pad clunk (thus the double spring, which solved it for me) and this manifests most likely when you transition from reverse to forward, like backing out of a spot and then starting out.
 
#10
Does your Canadian Sport have the “hillholder” function? Mine seems to generate some clunks at unexpected times, though it's always on hills; however I had the same feature in a manual transmission Subaru and it could be fooled into activitating on sudden braking at very low speed with the clutch in, especially in reverse ... presumably whatever inertial sensor detected an incline, was triggered by sharp deceleration at low speed and kept the brakes applied even after I released the pedal. I guess in summary, it could be brake pads/caliper, control arms, rear leaves, driveshaft etc but it could be triggered or exaggerated by one of the low speed traction, control, ABS, or hillholder function or malfunction. Or even CPS failure causing low speed surge that's being counteracted by the electronics? Has your CPS been replaced? But just brainstorming ... had no similar experience, other than rpm surge at idle which was most noticeable when coming to a stop, before my CPS recall.
 
#11
Do you have a GoPro or similar device that you can stick down there? May help you narrow down the location of the clunk, and if the sound is related to anything slipping or jerking you may even see it.

I'm a big fan of obtaining a positive diagnosis on a problem before I throw parts at it. It sounds like you've already solved the hardest part of a problem like this, which is being able to replicate the sound

Sent from my Pixel using Tapatalk
 
#12
If it is drive-line clunk, which it sounds like based on my experience, then your drive-line may be out of phase. If out of phase even a little, then there is an opportunity for the drive-line to bind rather than easily slide fore and aft as it should. As you come to a stop, you may be hitting the binding point. As you release the pedal, you give just enough for the drive-line to finally release and clunk.

I had a drive-line clunk with my 4th gen 4runner. I brought it up to the dealer every time i had it serviced with no change. I think after one service, it was actually worse. I assumed they dropped the drive-line for something and then didn't put it back the same way. When I took my 4Runner to a trusted mechanic to install new LCAs I asked him to look into the clunk. He had another customer with a Land cruiser with the same issue. Another tech of his performed the work, but as part of the completion process, he took it for a test drive to insure all is good. He noticed the clunk and decided to get under the truck himself and found that the drive-line was out of phase. He made the adjustments and since I have had no more clunking. It has been 2 years. If I bring it to Toyota now, I emphasize that if they touch the drive-line for any reason, it must be put back the EXACT way it was before they touched it.

I will say that originally, I never had any perceived vibration, but the clunk at stops was exactly as you described. Like someone tapping your bumper at a stop. Hope this helps.
 
#13
Slip joint in the driveshaft binding? My 4Runner did that. I greased the slip joint, which helped a lot. Replacing the rear driveshaft with a new Tom Woods driveshaft eliminated it completely.
 
#14
Thanks, everyone. Lots of good info to consider.

I'll have my truck in an off-road shop for a rear-bumper install in a few weeks, and will have them look at this, too. Much simpler to deal with these guys than the dealership on things like this.

A replacement driveshaft (from the very Tom Woods) is something I've considered, as I do have a bit of driveline vibration happening at 70-80kph. Although I'd do a single-piece to eliminate the Toyota two-piece, and the accompanying (problematic) u-joints.
 
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#15
Dealership finally found the clunk: driver's side, lower control arm - bolt was loose at the caster adjustor. Going to have to do an alignment, but I'm super happy that the source was found, and that nothing needs to be replaced.