Help Troubleshoot Pop sound fr/Lt wheel well on acceleration...pics

Troubleshoot help request: '06 2WD, AC,4.7 purchased @ 173600 [6/2024], today=177500K...

About 2500 mi's now into new LBJs, Outer Ties, End links & bush's, Stblzr Bush's, StrRack Bush's., Rack boots, clips & Bilstein 4600 x 4. Tracks straight, turns steady w/out wheel slop, quiet, smooth.
About 1500 miles back , towed 4500# boat/tandem trailer 150 frwy, flat road miles and launchramp [handled all like near new truck]; all other miles frwy or city streets [pavement queen].

Yesterday, started a dull pop sound at acceleration only- Single pop and nothing otherwise until next acceleration fr/full stop or very slow. Sounds like coming fr/Lt side and very repeatable.

Please take a look at the pics and comment if anything looks out of ordinary.
Only other thots I have on the Acceleration pop [or thud] is motor mount failure [Lt side].
The pics of wheel assembly and motor mount as much as I could get cam in at correct angle.

Thx for the inputs...ps

Lt wheel






Lt Motor mount [hard to get cam in there- sorry]

 

Will it make the noise if you floor it in neutral? Putting the rear axle up on jack stands would also help you figure out if it’s drivetrain or front suspension.

 

Going out to fire up in N but pretty sure only in D, at acceleration.
Ill confirm and report....stand-by.

Update: No sound in N revving.
Upon closer listening [while driving], sounds definetly fr/wheel well [or firewall] AND definitely on Accel and again, once foot off gas to start coasting. Same sound either way.
Doesnt do it at hiway speeds.
Only seems to occur at low speed, especially immediately after 1st to 2nd shift and again at the d/shift bk to 1 when beginning to coast.
Feels and sounds like coming fr/firewall or bellhousing. Im suspecting trans TC...IDK.

BTW: in this pic, looks like 2 fasteners are missing@ btm/Bell Housing ?

 

Have you inspected the transmission crossmember for cracks? Missing bolts? There’s a TSB for 2wd trucks on this issue.

 

IDK..unless I can magnaflux it, it looks solid. Some surface rust at join to fr/rail.

 

Look in here. Should be 4 bolts. No hairline cracks.

 

@KNABORES ..thx for the clue.

Hadnt thot of that, just b/c sounds are coming fr/ wheel well/firewall, at least when in the cab it sounds like that...
Gonna rack it up later today to get a good look at the X-member.

Sounds weird to say, but I'd be thrilled if it were just the X-member vs. FlexPlate, TC, anything tranny, etc....

 

I had some bolts that needed to be retorqued after working on the suspension that gave a similar dull pop/clunk at slow speeds. I retorqued them once, then loosened and retorqued them the next day and it solved the clunk.

I'd also check the UCA ball joint and bushings.

 

Sounds like my upper ball joint before it blew out on me. Any shakes in the wheel or weird tire wear?

 

Late Update :
Closer look while on rack at local driveline shop: all apparently good, including Trans support Xmember and motor mounts are good [for 19+yrs].
nt. No wheel shakes, shimmies, pulls...
Drive shaft/u joints in decent shape for 19+ yr/old. About 1/8" slop in the joint at the differential, but not horrible and not responsible for the dull pop sounds, and clean and reasonable at trans tail and the mid-support. Yes, theyre all originals and should be updated sooner than later, but mechanic cant see how theyre responsible for what we're hearing.
On mechanics test drive did several tight circles w/wheel full lock, Lt & Rt - sounded off only at start and sounded same for either direction.
Also sounds off when brakes applied and released while in drive: about like advancing in a fastfood waiting line.
Lunged throttle a few times w/foot on brake to check motor shift, lift, push and all looked good and didnt produce the dull pop/thud sound.

So, will see mechanic who did the suspension rebuild tomoro AM to troubleshoot. Everything he did [shown in #1 above] has been doing excellent for the 2500-3000mi's so far, [including the 150 mi's of towing] with all Toyota parts.
The only other thing I could possibly suspect, based on the kind of pop/thud I hear, is what maybe a failing shock mount might sound like but all I can see is the bottom end and they look properly seated and bolted.

Almost think it may be brake related since its easy to repeat the sound by staying in drive and hitting/releasing brake for short hops.
Driveline mechanic said it sounds/feels like caliper bolt is loose. OTOH, it may just manifest more obviously by braking action, or anything that suddenly loads and unloads drive train torque on the frt UPPER suspension... Gonna pull wheels this week and check brakes.

@blenton ...I'll make a point of mentioning all that; btw, UCAs, UBJs, etc: all original, so wouldnt be big surprise if thats the problem source...
@RustyMcTee ...that makes 2 votes on UCA parts...
Im starting to believe this.
Ill update in a couple days- got a new d/washer install tomoro so theres half day gone...