Noise identification lol good luck

[usar17]

SO....

When I first bought this truck and really started driving it a round more then the PO I began to notice a loud tapping from either under me or behind me. Sounded like large metal clanging together a lot, like vibrating. I feel nothing in the line of the truck shaking.

This started off only doing it on occasions when i would quickly go from gas to a hard brake.

Since purchasing the truck i have changed the rear diff fluid and tranny fluid/filter. Thats it from behind the engine.

The truck now seems to do it more often whenever i let off the gas, mainly at highway speeds. Shifting to neutral does nothing. While in neutral reving the engine does nothing. But if i give it gas while still in drive the sound goes away till i let of the gas again. Sometimes it stops, sometimes i have to REV it a couple times till it stops.

Thoughts? Tranny or driveline? My only thought is U-Joints but the shaft doesn't seem loose if i just crawl under and try to spin it.

 

[usar17]

O ya...I also always hear a single clunk when I drop it in gear and start to pull away.

 

[foamypirate]

Kind of sounds like it might be the rear diff.

 

[89Suburban]

SO....

When I first bought this truck and really started driving it a round more then the PO I began to notice a loud tapping from either under me or behind me. Sounded like large metal clanging together a lot, like vibrating. I feel nothing in the line of the truck shaking.

This started off only doing it on occasions when i would quickly go from gas to a hard brake.

Since purchasing the truck i have changed the rear diff fluid and tranny fluid/filter. Thats it from behind the engine.

The truck now seems to do it more often whenever i let off the gas, mainly at highway speeds. Shifting to neutral does nothing. While in neutral reving the engine does nothing. But if i give it gas while still in drive the sound goes away till i let of the gas again. Sometimes it stops, sometimes i have to REV it a couple times till it stops.

Thoughts? Tranny or driveline? My only thought is U-Joints but the shaft doesn't seem loose if i just crawl under and try to spin it.

What is the speed of the sound? Tire speed or engine speed or drive shaft speed?

O ya...I also always hear a single clunk when I drop it in gear and start to pull away.

Yeah, me too, I hate it. And when I shift into reverse sometimes.

 

[usar17]

hmmm idk lol. kinda like the jake brake on a diesel but metal clanging. so i guess engine speed lol

 

[89Suburban]

hmmm idk lol. kinda like the jake brake on a diesel but metal clanging. so i guess engine speed lol

Yikes. I would think a U-Joint would be a more of a squeaking sound. Is it an auto trans? Only thing I can think of with that description is maybe some loose converter bolts? I dunno....

 

[HotRodPC]

Sounds like a U joint to me all day long. And you're sure your Tcase is in Neutral when this is happening?

 

[usar17]

Well...I'm currently broken down on the side of the road now Hahaha. Guess ill have to tear everything apart and find out wtf is going on

 

[HotRodPC]

That sux. Is the driveshaft hanging down?

 

[crazy4offroad]

If nothing else it could have been a t-case chain link breaking. Hate to hear it laid down on ya before you could finger it out.

 

[HotRodPC]

So where's the update buddy? Did you get it towed home? What's the verdict?

 

[usar17]

Got i towed to the Fire House where I work. I've never really used the transfer case and never thought of that. When i said i shifted it in neutral i meant the tranny. It seemed the only way to get rid of the sound was to put some torque on the system.

Well i was on the interstate and notice everything was stopped. So i decided to hit the exit ramp. Well as soon as i took my foot out the gas (which was probably around 2000rpms at the time) and hit the brake i had a three clanks then boom. No power. Coasted off the ramp.

Drive shaft is still connected. No spinning while in drive. Putting it in park didn't hold it, i had to set the parking brake.

Now when i give it gas it just sounds like the engine rev'ing in neutral.

That's all i got from last night. Ill have time tomorrow to look at it a little. but probably wont get to breaking things down till next weekend.

 

[crazy4offroad]

That sounds to me like the t-case blew. Sucks man but at least it may be an easier fix just remove & replace the bad unit compared to rebuilding a trans or finding/getting it rebuilt.

 

[HotRodPC]

Did you try to put your Tcase in 4 hi and see if it moves? If it moves in 4 Hi, you rear end is trashed. If it doesn't, your Tcase is trashed. All of which can be fixed with used parts off of CL for about $100-$150. For either A 10 bolt rear end or a NP208 Tcase. Might even just be spider gears in the rear end and you can handle repairing that yourself. But you say this noise was coming from under your seat? IF so, more like Tcase is broke.

 

[crazy4offroad]

He said driveshaft doesnt spin in drive.