Chirping from rear end...

[doodah man]

Recently, I started noticing a chirping sound that seems to be coming from the rear of the truck. It only occurs when the truck is rolling. The frequency changes with speed and stops all together when I press the brakes. Is there a wear indicator on the rear drum brakes that might be sounding? Any ideas would be helpful. Thanks in advance.

[TBONE1964]

No wear indicator for rear brakes. That is a good idea though. I would guess from the wording you use "chirp" that you have a u joint that is getting rusty inside. I am thinking you hear a " chirp chirp chirp" and the chirp gets faster as you get going faster and you probably don't hear it much when you are going around 40 - 50 mph but more at low speed.

I could be wrong but otherwise, jack it up and roll the rear tires and see what you come up with. It may also be a peice of rust on the brake backing plate or drum that has come loose.

[doodah man]

You're right. It's a "chirp chirp chirp" sounds. It's easiest to hear when decelerating/coasting, but stops when I press the brake. I did ride in the back of the truck and couldn't tell which side it was coming from which might point to the u-joints also.

I would think though that noisy u-joints would be unrelated to brakes being pressed so long as the truck's still rolling. Anyway, I'll give it look see. Thanks.

[68gmsee]

Yeah, could be either of those -u joints or brakes.

Lube the joints (easier to do) if they have grease fittings and see if you notice a difference. Or raise rear axles and place on stand one side at a time. Start the truck to see if you can hear the noise. Just use caution and chock tires.

If you don't hear the chirp, it might be ujoint since they usually act up when under load.

[TBONE1964]

Originally Posted by doodah man

You're right. It's a "chirp chirp chirp" sounds. It's easiest to hear when decelerating/coasting, but stops when I press the brake. I did ride in the back of the truck and couldn't tell which side it was coming from which might point to the u-joints also.

I would think though that noisy u-joints would be unrelated to brakes being pressed so long as the truck's still rolling. Anyway, I'll give it look see. Thanks.

Are you sure it is not coming from the front? It sounds like it may also be a disc brake pad indicator noise and those usually stop making noise when you apply the brake. It depends on the speed. If you are rolling lets say 25-30 mph and just light tap on the brake and the noise goes away, it may be brake pads. I have never heard of this on rear drum brakes but not saying it is not possible. I do know that there is no wear indicator for drum brakes.

[Ol Blue K20]

Sounds like a u joint to me..

[68gmsee]

Depending on the "chirp" I had a brake shoe that was too close to the drum making a scratching type of noise.

[doodah man]

Not 100% sure that it's coming from the rear, but it sounds like it. According to my doctor, I've got the hearing of a 60 y.o. (I'm 37, ), plus dual turbo mufflers. I hope it's not the front brakes, since I just put new pads on less than a year and ~12K miles ago. Anyway, I'll check both and try jacking it up and spinning the wheels to see if I can more precisely locate the source of the sound.

[o6r1man]

U-joint
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[LONGHAIR]

Definitely the U-joint. The chirp changes because of the load on the joint. Some do it during acceleration and not when coasting, others are opposite. At this point the needles are rusty and dry, soon they will crumble and you will have a clunk when going into reverse.

[doodah man]

I just wanted to update and add some information.

The sound quit 2 days ago and hasn't come back. Fixed...

Also, the u-joints are about 2 y.o. and have only 22K miles on them. I will crawl under this weekend and wiggle stuff around, but is it reasonable for them to go that soon.

[Ol Blue K20]

I"m sure they haven't healed..it just might be the calm before the storm..It depends on how tight they were and lubrication. I've seen one cup that was tighter than the others and not take grease and wear out quickly..

[Eddie H.]

When I was working in dealership, a customer brought in a pickup complaining of a growling coming from under the hood. I opened the hood and found a very unhappy racoon

[Ol Blue K20]

Originally Posted by Eddie H.

When I was working in dealership, a customer brought in a pickup complaining of a growling coming from under the hood. I opened the hood and found a very unhappy racoon

Uh oh I can fix it..

[TBONE1964]

Just a FYI, a u joint that is tight will make more noise if it is dry. Usually a u joint that is wore and has play will clunk but not chirp with rotation. The chirp comes from dry needles. The only way to really check it is to pull the shaft(s) out and see if the have restrictive movement. I would bet that if the chirp has stopped, the clunk will soon follow.
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[doodah man]

Originally Posted by Eddie H.

When I was working in dealership, a customer brought in a pickup complaining of a growling coming from under the hood. I opened the hood and found a very unhappy racoon

Ha! Maybe the birds nest finally fell off my drive shaft.

[doodah man]

Originally Posted by TBONE1964

Just a FYI, a u joint that is tight will make more noise if it is dry. Usually a u joint that is wore and has play will clunk but not chirp with rotation. The chirp comes from dry needles. The only way to really check it is to pull the shaft(s) out and see if the have restrictive movement. I would bet that if the chirp has stopped, the clunk will soon follow.
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TBone, GMSee, I hear a clunk when I go into reverse already. I've never changed the u joints myself. The tranny shop put the existing ones in when they resealed my trans a couple years ago. Would you say this is something I can get done in a day? Based on the instructions I've seen, it seems doable. I just don't have the option of leaving it pulled apart for more than a day (no garage, so the work has to be done at brother-in-law's house or on the street).