Very loud knock out of nowhere!

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Hello, new to the forum hoping to save my beloved truck. It's a 1998 2500 5.7 with a 5-speed. I bought it in the spring and first thing I did was check the fluids. The previous owner said he had just changed the oil and it looked brand new. Stupidly, I never checked the oil again. About 5,000 miles later I went to change the oil. I put the truck up on the lift and noticed the drain plug was leaking. I took the plug out to find a little less than 3 quarts of oil. I was mildly concerned but I never had lost oil pressure or anything, so I figured it was fine. I changed the oil, got a new O-ring for the drain plug and all was well. About 500 miles later, I was driving up the steepest mountain in Western PA. The usual for climbing this hill is 4th gear, foot to the floor, to pull about 75mph up the hill, (About 5 miles long). This time I was hardly able to keep it at 55 and almost had to drop down into third. It was definitely down on power, but according to the gauges, all was well. Wasn't making any bad noises either. After 20 more miles of steep grades, it started to tick, I only had 5 more miles to go so I began to take it easy. By the time I got to where I was going it sounded like a jackhammer on metal.
(Sounds just like this...
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I called a tow truck and had it towed home. There's no metal in the oil and the truck only has 140,000 miles on it. This truck is in great shape and was obviously well taken care of long before I had it. I'm sure it's probably a rod, but before I go engine hunting, any other ideas? Thanks.
 

Justin S

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Yeah, something is on its way out internally if it sounds like that, I had a 350tbi blow up on me once, right before it did, it sounded like someone put a bunch of rocks in a washing machine. My guess is a rod bearing is gone, and the piston is slapping the head. If you change your mind about engine hunting, I have cash :p I'm in the market for a 5spd 2500
 
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Tempting... How much cash we talking? It's a pretty clean truck. Only thing I know it needs (other than the engine) is a sway bar link. A/C doesn't work either. Everything else works great. Blue on blue. Interior is really nice aside from the classic tear on the side of the drivers seat.

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Justin S

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Not sure, i'm in NY and would have to tow it obviously, throw out a number! It does look like a nice truck.
 

Ironhead

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Not wanting to throw a wrench in the gears here, but if this is really a beloved truck, why would you sell it, rather than repair it? If I were in this situation, I'd be looking into getting a crate engine, but of course, it's always easy to spend other folk's money...
 

Biggershaft96

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Not wanting to throw a wrench in the gears here, but if this is really a beloved truck, why would you sell it, rather than repair it? If I were in this situation, I'd be looking into getting a crate engine, but of course, it's always easy to spend other folk's money...
Amen to that! I love spendin money that aint mine lol. Yea that definatly sounds like its gonna need a new motor but its nice truck so someone is bound to put a motor in it.
 

kennythewelder

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It sounds like a rod knock. Time for a new engine, or a rebuild, but it is hard to say for sure with out being there to listen to it in person.
 

mistaake

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It's easy to say this when I'm not the one paying for it but that truck looks really clean and worth dropping in a crate engine IMO.
 

SAATR

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Start pulling plug wires one at a time, listening for a change in the sound. If it never changes, it isn't a rod.

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