Mystery clunk when turning - SOLVED

Posting this for others that are also suffering from a mysterious clunk from their front end when turning (especially when backing up). Maybe someone already figured this out, but I couldn't find a similar explanation while searching, so here it goes...

This may not be what's causing your "clunk", but it's what was causing mine!

Backstory: For the last ~1 year I've had this mystery clunk come from the front of the truck while turning. I don't know exactly when it started, but it was sometime post-lift (~+2.5" FR and RR with aftermarket coils and AAL). It always occurred at full steering lock. I did a lot of searching here and elsewhere online, inspecting the truck, making sure everything was torqued to spec, making sure parts weren't worn, etc. to figure out what it was. No dice.

Most common answers seemed to be sway bar related, loose LCA bolts, loose steering rack bolts, or bad ball joints. All were good on my truck, which stumped me for a while.

That was until I did a closer inspection of the lower steering knuckle attachments. I noticed an odd wear pattern on the steering stops. The steering stops on the knuckle side showed wear primarily at the top of the stop with some minor wear in the middle of the stop, but none at the bottom of the stop. It's easy to tell that this wear is from suspension articulation while the steering is at full lock (from the stop on the LCA contacting the stop on the lower attachment of the steering knuckle). Everything moves a surprising amount when hitting any change in surface elevation, even when the steering wheel is static--so at full lock, it makes sense that it would show some wear. The real question was why wear was present only on the top half?

Because of my lift, I surmised that the steering stop on the LCA wasn't hitting the stop on the knuckle in the correct position, resulting in the observed wear pattern. For those that are familiar with our front suspension/steering setup, you know that the LCA side steering stop is slightly convex, and stop on the lower attachment of the steering knuckle is slightly concave with flat spots on either side of the concave section.

Not the best picture, but you can see what I'm talking about on the DS side here:



It turns out, that, with the lift, the stop on the LCA side would initially contact the topmost flat spot of the stop on the knuckle side when the steering was at full lock, instead of on the center of the concave section of the knuckle stop (as it would at stock height, presumably). When the truck starts to move (usually in reverse in my case as that's typically the only time at full lock, e.g. trying to maneuver into a parking spot or something similar), the stop on the LCA side stop would become "stuck" on the topmost flat on the knuckle side, causing the suspension to bind. Eventually the force of the truck moving with the wheel at full lock would become too great and the stop on the LCA would slip off of the flat on the knuckle and into the concave section of the knuckle stop. This caused the suspension to suddenly "unbind" and the stop on the LCA to slam against the concave section of the knuckle stop, resulting in the nefarious "CLUNK".

I verified that this was the cause of the clunk by first attaching a peice of EPDM to the lower knuckle attachment stop to prevent binding and then driving the truck over various curbs/dips/etc. at full lock. And the clunk disappeared.

I tried it again to confirm, this time just spraying some PTFE dry lubricant on both the LCA side of the stop and the lower steering knuckle side of the stop--to allow a smooth, lubricated transition between the flat and concave sections of the knuckle side of the stop. No clunk.

So if you have a clunk on your front end when turning at full lock, this might be the issue. Just wanted to share my experience in the hopes that it might help someone else searching for this in the future.

If not hey, then I'm just documenting my struggles.


TL,DR: Front end clunk caused by steering stops binding the suspension at full steering lock. Solution - don't turn at full lock (or lube your stops I guess).

 

So I have been herring this for awhile now. I have done a lot of work to my 2012 Tacoma and replaced almost all suspension parts. I have a 3in lift and run 6112s up front camburg uca changed out cv axles and replaced tie rods inner and outer as where all worn. took care of all that and most issues gone. still had this mysterious clunk when at full lock out with steering wheel. mostly pulling into and backing out of parking spaces. like i said i noticed the Knuckle wear today. did a search and your thread came up. Sure enough it all makes sense. My question is do you just lubricate it all the time or is there a more permanent fix other than lowering the truck which obviously i am not going to do.

 

Glad the info helped!

I haven't implemented a permanent solution yet. For the time being, I have just avoided turning at full lock. If I ever feel the stops through the steering wheel when I'm turning, I just back off a few degrees and the proceed as normal.

I've been playing with the idea of taking an angle grinder to the LCA side stop to change the contour of the stop, but TBH after changing my driving habits (i.e. doing the what I described above), I haven't really pursued a permanent option. That being said, I have noticed that the PTFE dry lube does last a while (unless you're constantly hitting the stops). Sorry I couldn't be of more help!

 

Its just good practice to not hold any vehicles steering tight against full lock.

 

Yep, pretty much. I honestly had the truck turned at full lock for more time while testing this whole issue out than I ever had while actually driving.