Assistance with Driveline Noise Diagnosis?

Truck specs: 1996 Tacoma, 3.4 V6, 4x4, Extended Cab, Automatic Transmission (A340F), 220,000+ miles. All zerks greased at every oil change.

Getting a weird almost grinding sound from the truck when I feather the accelerator. Happens briefly when I engage and when I disengage the gas, especially more pronounced at highway speeds.

Forgive the extra road/wind noise on the videos, you can likely hear what I'm talking about nevertheless.

Recording from inside the cab:


Recording from under the truck with a loaner GoPro, you can really hear things rattling around when the truck is under acceleration in this one:


My simple mechanic knowledge tells me that this could be a bearing going bad and making some noise under torque? Pinion bearings in the (stock & open) rear differential, perhaps?

Appreciate any input you guys might have. I've had a few gremlins in the truck as of late. It's old, but I like it to work real good. It's busy season for auto mechanics around these parts and my driveline guys can't get me in for over a week. Thought maybe you good folks at TW might have some insight to help me diagnose whats going on. Trying to iron out some kinks before driving cross country in less than a month.

Thank you!

 

put it up on jack stands ALL $ Corners

get Under start twisting on Sh!t !!

notice i Did NOT SAY With The ENGINE ON >>>>>>>>>>>>>>>>>>>>>>>>>.

 

Man, even if I had room in my apartment for a decent jack and some stands, I can’t really lift the whole shebang up on the street here in Brooklyn.

But you’re right, that’s gonna be the best way to find out instead of just posting some noise on here and asking “which one of ten or so moving parts do ya’ll think this is?”

 

wasn't putting U down for livin in Brooklyn...………………………...didn't know

still if U find out whats wrong

got to have elbow room to fix

little loose here...…………………….lil slop there adds up

U got 2 be able to narrow it down

good luck

 

@ROAD DOG I didn’t get the put down vibe from you at all! NYC can be a fun place to live, but a real pain if you want to tinker with vehicles. I might use my bottle jack and some stands on the rear this weekend and get things jiggled around a bit.

 

How did you mount the GoPro camera?

 

On some fancy three jointed clamp thing my friend in rigging let me borrow. On an exhaust hanger, if I recall.

 

At least get the rear end on jacks and try to reproduce the sound .
If that doesnt work ,I suggest popping the rear driveshaft off , then selecting 4x4 and taking the truck for a test drive . This will place the load on your front driveshaft and front diff rather than the rear driveshaft and rear diff
If the noise does goes away , this will also eliminate the center bearing on your rear driveshaft .
Noises can be deceiving over a keyboard

 

Thanks, @gearcruncher. I’m in MT now, so have the opportunity and space to actually wrench around. Have had it up on jacks and given everything a good wiggle and spin, but can’t reproduce the sound while it’s stationary. Had a tech from a local shop do a ride along and his response was “well, that’s a new one to me.” He couldn’t figure it out either, but also didn’t remove the driveshaft.

I’m also considering posting up on the Montana thread to see if anyone in the area has a chassis ear type thing they’d let me rent/use/borrow so I can listen in to various areas while the truck is in motion.

 

It doesn't take much to remove the driveshaft .
I believe you need two 14 mill wrenches and a quick blast of paint for driveline indexing .
You could essentially hang the driveshaft in the disconnected position if you have bunjee cords

 

I actually just did a quick variation of this, removed the rear end of the shaft to give the rear slip yoke a good greasing with that blue Ford stuff (it was pretty dry in there). Used the bungees to hold her in place. You’re right, it’s a quick job. On my list for this week!

 

Ok, after a lot of messing around the noise is coming from the rear diff. A mechanic back in Missoula hypothesized that the ring & pinion lash might be off, and that it’s knocking the gears around while they float in the brief moment when they’re not under torque one way or another.

Bummer, as I just had the rear diff rebuilt a few weeks ago to try and get rid of this exact noise (which made me think it wasn’t diff related this time around). All bearings got replaced, but the original ring & pinion were reused. En route back east now and taking it back to the NYC shop that did the original work this Friday to see if we can’t get this finally sorted.