faint noise with throttle off

[brucec039]

I'm sorry if this has been covered, but I'm not sure what keywords to search under.

After 20K miles my 07 prerunner V6 auto doublecab TRD offroad pkg is putting out a noise I haven't heard before. It is a faint "whoomp whoomp" that mirrors the speed of the vehicle (slowing as vehicle slows) but is only audible at lower speeds like when coasting or braking to a stop. I can feel a slight vibration in both pedals, but it's not very pronounced like with warped brake rotors and often occurs with no brakes applied. It does NOT, however, occur when accelerating. That leads me to wonder if it is some sort of problem in the driveline that involves slack. It sounds almost as if there is a flat front tire but I cannot discern where the noise is coming from.

I suspected my anti-roll bar had come loose, but it seems to be ok. Same with helper springs, no movement there. It's had about 100 miles on it since I noticed it with nothing getting worse. The slight noise and vibration is not always noticeable, but is definitely there as I coast to a stop. And as I mentioned, it slows in rhythm as the truck slows.

Any ideas what I have here? I'd hate to take it in just to find out it was something stupid I should have checked. This vehicle has had zero issues before in fairly heavy duty use.

[the.phantom]

next time, just bump into neutral and do you still hear it?
that would narrow it down a bit ( not engine,tranny)

what about U joints? lubed and in good shape with not excessive play?

tires/rims/lug bolts?

have you had someone "chase you" and when it happens stick you had up and he can check out all 4 wheels

do you have a lift kit on it?

[brucec039]

Originally Posted by the.phantom

next time, just bump into neutral and do you still hear it?
that would narrow it down a bit ( not engine,tranny)

what about U joints? lubed and in good shape with not excessive play?

tires/rims/lug bolts?

have you had someone "chase you" and when it happens stick you had up and he can check out all 4 wheels

do you have a lift kit on it?

Some good ideas, thanks. I did try putting it in neutral but not at low speed which I should have tried since that's when I hear the noise.

I haven't done any service on the u joints, and I wouldn't even know how to tell about excessive play. My next step is to check the lug bolts. I do have aftermarket wheels/tires on it and never had it realigned but it's been 12,000 miles with no noise till now. No lift kit.

Do wheel bearings ever start to go out at 20K miles?

If I can't figure it out tomorrow I will schedule a trip to the dealer.

[brucec039]

Lesson: Thoroughness pays. I was slack when I inspected the tires and today I was more careful and I found what looks like one of those nails used to hold foam insulating sheathing on homes and the metal cap on top of the nail was causing the noise. It was slightly hollow which only added to the volume it put out. I knew a regular nail/screw would not make that noise so I had discounted it. I guess the nail and cap had been facing down on the pavement when I checked it before. That tire had been a couple lbs low which should have been my clue, but I was tired and lazy and ignored it. Lesson learned.

So no driveline or suspension worries and my Tacoma remains trouble free at 22 months and 20K miles.