Ok, I have in my garage right now an '03 Durango with a 4.7 that belongs to a nice couple in Kansas. I brought it to my place because it needed a wrist pin replaced on a cylinder...I know the noise of a sticky wrist pin quite well, diagnosed the problem by ear in 5 minutes, brought it here, pulled the axle, pan, head, verified the diagnosis, did the repairs (along with a number of bad lash adjusters and 2 valve seats), put it together and it ran perfect...until it warmed up and I got a slight thunking noise coming from the top rear of the engine. So assuming it was another loose seat on the other side of the engine, I pulled that head and found that the piston is tapping the head after it warms. Obviously, the noise was masked by all the other racket it was making before the repairs were done, but here's the thing: I checked all the rods for play, and found none. All were tight, oil pressure is perfect, and there was absolutely no noise coming from the bottom end of the motor. So I'm thinking either the rod or piston are malformed (unlikely it's a crank problem, at least in my opinion, with only 1 piston hitting), but I'm trying to figure out if this is common (read about it in only one place so far) and what the actual cause of it is. I read an absurd answer from an idiot on another forum about the timing chain causing the piston timing to be off....couldn't believe the stupidity even as I read it....but nobody with actual experience with this engine spoke up and I saw no reason for this to occur.

Anybody else have this issue, ever? This 4.7 is a bit foreign to me, I've dug into the Dodge V6's that are similarly designed but this is the first 4.7 overhead cam V8 I've pranked with, and would like to hear from a real 4.7 Guru. I haven't spoken to the owners yet, and when I call them tomorrow, I'd like to give them a reason behind the problem rather than discuss the symptom itself, whatever that turns out to be.

Any information appreciated.

 

I've never dug into a 4.7 before, but I'd agree with you that it's probably either the con-rod or the piston.

 

just my idea. if the engine was over reved. it might that all the con rods could be damaged. sounds like time to measure all the conrod lengths, and check for cracks. same for the all the pistons. cause you said it had other damage. sounds like over reving to me.

 

It's possible, I suppose, but given the driving habits of most women with 4 or 5 children, I'd say it's less likely than a combination of flawed design, and relatively poor maintenance...not horrible, there's no sludge buildup, I'd say just going a little long between changes on average.

Haven't gotten into it yet (motor's coming out pretty quick, will know more then) but I'm guessing it's either another wrist pin, or deformed rod. I considered just pulling the diff and pan again, but with both heads and exhaust already off and out of the way, it's just as quick at this point to jerk the motor, and with the slight possibility of it being a rod, I'd rather just pull it now and have it out in case the crank needs to come out.

 

I doubt it's due to a design flaw. I've never heard of this happening before with any of these motors. I think it's entirely possible that it was over-revved. And quite a few mothers drive with lead feet (ask me how I know). Poor maintenance could be a cause too.

 

I have never heard of this issue before. Just throwing this out there but have you check the new head gasket thickness? Amazing what a couple thousandths of an inch will to. I know some guys will play with different head gaskets when doing performance builds, cam swaps, new heads, ect. cause of the tolerance.

 

It sure as heck sounds like a "Stretched rod ! If the rod was deformed it would have been doing it since day one !

 

I've seen it before, one 4.7L had the same issue. There would be 2 things I would be looking at.

1. Measure your clearance on your main and rod bearings. Being warm the oil would flow more freely and if there is any play it could kiss the head. I would install new bearings with tight clearances.

2. Check your wrist bearing.

Also if you had the head ground it could be too close now to the piston. But I'm thinking ware is your culporate.