Low Speed Popping Sound

[Dr Phat]

Hi All! Never really got around to updating my build here, but for you all still here Id rather hear your opinion before turning to the cesspool of Facebook groups.

1988 Toyota Pickup, SAS with '84 Pickup Axle, 6.5" lift, Dual Cases.

The truck runs great, and drives smooth. The only issue I cant figure out right now is what is causing a popping sound. I have a EZ Locker rear, and spooled front. I dont think its the rear locker though because the noise I hear happens when Im going straight.

Anyway, when coming to a stop, I heard a popping sound. Its not related to engine speed. I dont think matters whether the transmission is in gear/neutral, or clutch pressed in and out. But it also happens at only such low speeds its hard to really diagnose whats going on because the truck will stall out otherwise. The sound seems like its coming from the passenger side transmission tunnel. If I rotate the front driveshaft by hand without the hubs engaged I dont hear it. The popping dosent turn into a whine as speed increases or anything. My next thought is to jack the front axle up and spin the wheels and see what I hear. Its just hard to figure out the noise as it seems to only happen on deceleraton coming to a stop. Anyone have any other ideas what I should check? Could it be the locker and Im just overthinking it?

[Ritchie]

You stated that you have a 'spooled front'. I would start looking there.

[Dr Phat]

I don't think this would make a difference though no? It make the noise in 2WD with the hubs not engaged and only when decelerating especially in a straight line.

[Prismo]

check your u-joints

[Dr Phat]

They're brand new from Tom Woods 😅

[OVRAROK]

Just a thought  Are you sure it's drive train related. I've seen exhaust leaks that make popping on decel

[Dr Phat]

I'm fairly sure because if the truck is left in gear and allowed to come to a stop/stall I don't hear it. If I blip the throttle when coming to a stop the pop dosent change in frequency or stop. It's related to speed and/or drivetrain turning.

[OVRAROK]

Chassis ears may help locate problem

[a1gemmel]

Happens only with brake pedal depressed?

[Dr Phat]

Happens only with brake pedal depressed?

Seems to be so. I jacked up the rear axle and couldn't replicate the noise by putting it in gear and depressing the clutch. The clunks from manually spinning the wheels sounded similar. I couldn't get the truck to make the noise in any combination of low range gears.

Chassis ears may help locate problem

Good idea! Don't  know anyone local with one but maybe I can but a cheap one.

[Rocksurfer]

When it makes the noise does the truck shift its position?

[Dr Phat]

No I can't feel the noise, only hear it.

[Gnarly4X]

Remove the rear drive shaft.

Put it in 4-wheel drive.

Lock the hubs.

Test for noise.

Gnarls.

[Rocksurfer]

I have a little thunk on the freeway in traffic only. As I coast along it is constant but goes away on acceleration, looked at everything and can't find anything that would cause it. Been that way for years, it drives me crazy thinking something is wrong. If I disconnect the rear ds it goes away, did the ujoints still does it. I've come to 3 things it may be, a defect it my R&P, my CV or driveshaft may not be true anymore. Has never demonstrated where it is coming from. Can't replicate it on testing.