Help! This sounds expensive...

[tuberbob]

So I was driving my truck about a month ago, and all was well. It's a 1990 v1500 Suburban, pretty much stock. I drove to a customer's house, was there for about 45 minutes. When I left, I started hearing this crazy metal on metal noise. It only happens under acceleration, and its pitch changes as RPMs change. When I placed the truck in neutral (while underway) and revved, everything was normal. As I was coming home, I pulled out the phone to record a video, purely for the audio. I am attaching that video.

I live up a hill, so you'll hear a period where it goes quiet. This is me coasting as I make 2 turns, as I finish the turns, I put the phone outside, and it becomes really clear.

At any rate, I am hoping someone here can steer me in the right direction diagnostically, because I don't even know where to begin, I just know it doesn't sound great. Thanks in advance.

video link: https://vid.me/tubB

 

[Camar068]

ujoints?

 

[1987 GMC Jimmy]

That sounds viable. Get under it, grab the driveshaft good, try to rotate it, and see if it has any centrifugal play in it. With good universal joints, there should be zero movement. Here's a good video demonstrating what to look for.
[yt]xqSwmwUfoLE[/yt]

 

[87ChevyR10]

I would have to disagree on the u-joints. I had mine replaced last summer and they were original and never heard anything like that.

Bad u-joints typically have some play in them and usually make a distinct chunk/**** sound when put in drive or reverse. That sound typically emanates from the pumpkin.

Another reason I disagree is the fact you say the noise stops when coasting in neutral. The driveshaft doesn't magically stop spinning once in neutral. After watching the video, the sound seems to be coming from the front of the vehicle. Is it 4WD? If so, I'd be looking at the transfer case, hubs and steering components. Try to get the vehicle elevated and reproduce the noise. This will help you and us give you better help.

 

[bucket]

I would have to disagree on the u-joints. I had mine replaced last summer and they were original and never heard anything like that.

Bad u-joints typically have some play in them and usually make a distinct chunk/**** sound when put in drive or reverse. That sound typically emanates from the pumpkin.

Another reason I disagree is the fact you say the noise stops when coasting in neutral. The driveshaft doesn't magically stop spinning once in neutral. After watching the video, the sound seems to be coming from the front of the vehicle. Is it 4WD? If so, I'd be looking at the transfer case, hubs and steering components. Try to get the vehicle elevated and reproduce the noise. This will help you and us give you better help.

A sticking u-joint can cause noise only when on the throttle. Usually it's a squeaking type noise though.


Something is loose under the truck. The axles and driveline need a good lookin over.

 

[87ChevyR10]

A sticking u-joint can cause noise only when on the throttle. Usually it's a squeaking type noise though.


Something is loose under the truck. The axles and driveline need a good lookin over.

OP's truck was still making noise on decel, too. I still think something in the front-end is wrong since the OP's burb appears to have selectable 4WD and that's where the sound is emanating from.

Best thing OP can do is get all 4 wheels off the ground and have someone run the vehicle while they try to pinpoint where the sound is coming from.

 

[bucket]

As bad as the noise is, just crawling around under the truck for a basic inspection should reveal the problem. Unless of course it's an internal t-case or diff problem.

 

[tuberbob]

Thanks everyone, I appreciate you taking the time to respond. I haven't had a chance to get under it yet, I am going to try to do that this afternoon. I will report back with whatever I find.

 

[tuberbob]

Well, I had the truck towed, and it seems my rear end grenaded. I have no idea yet how extensive the damage is, but I guess now is the time to consider a locker for the rear end.

 

[bucket]

Yep, you were right. 'Spensive. Got a Gov-Loc G80 that 'sploded? I'd be interested to see a pic or two of the carnage.

 

[87ChevyR10]

Ouch! I had the spider gears replaced last summer. Cost me $708 to replace them and u-joints. Glad I got them replaced, otherwise, I'd be in the same boat. Mechanic really wanted to rebuild whole rear-end, but said most of the play was in the spiders gears and u-joints. I had the truck up to 100 mph (6 o'clock on speedo) once and the rear-view mirror shook so bad, you couldn't see anything in it.