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Help! 2004 Yukon, big bang on 3-4 shift and sudden engine death

jonrpick

jonrpick

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2004 Yukon XL, 5.3, 2WD... Getting on the interstate last night, was manually shifting to get up to speed. All was fine until the shift from 3rd to 4th. Heard a loud BANG, followed by a grinding noise (sounded similar to the parking pawl trying to engage while still moving). I was already over 70mph when it happened. RPMs dropped to zero immediately as I was pulling off to the side. Tried to start it just to listen. It'll rotate fine but won't start. Tried again today and when turning over I heard a loud clunk/bang. Not doing that again, though the damage is likely done.

Turning the key to the RUN position, the dash never comes alive. It should at least show fuel level, Service Stability Control, etc... should it not? All I get is a check engine light. Pretty sure it would at least power on the instruments before.

Currently waiting on a rollback to get it back to my work parking lot.

Any ideas what I'm in for? Sad part is, it's the ex wife's truck (with a lot of my own time and money in it). She doesn't drive it anymore. It was a life boat that I got back on the road last month after my Equinox ate the timing chain and consequently, the valves.

What do? Brotherhood, I beseech thee.
 
Not sure why elec is out.
Other best case flex plate.
After that could be anything possibly torque converter
 
I had a transmission go out on a work truck once, same type noise. Engine would not turn over, but there was noting wrong with the engine.

We've also had a van at work that had a trans failure at highway speed, engine shut off and it got towed in with a hole in the side of the transmission case.
 
If the flex plate jammed it self together, the crank sensor would have seen weird signals,and shut down.

Or maybe what ever broke damaged the wiring to something important
 
I wonder if the starter got dislodged or the associated wiring damaged.
 
Fastereddie said:
I wonder if the starter got dislodged or the associated wiring damaged.
Click to expand...

The starter is engaging and turning the motor over. But there's a noticeable clunk noise when that happens and it won't actually start or run.
 
Just trying to figure out what took out the electrical
 
Fastereddie said:
Any fluids showing themselves?
Click to expand...

Just oil from leaky valve covers.

Fastereddie said:
Just trying to figure out what took out the electrical
Click to expand...

Me too. It's only the dash cluster though. Even the digital display isn't coming on. Very weird. Now I will say, that dash cluster does act up. Sometimes it doesn't come on immediately when you start the truck. Sometimes there's a 30-second delay. But I know that there are some issues with corrosion on the interior of the truck due to it sitting for so long and it having a ton of moisture in there.

Nothing that would've caused banging and grinding noises. Like I said, the initial event happened right as I shifted from 3 to D. And no, I didn't miss D and skip onto R or P.
 
jonrpick said:
Just oil from leaky valve covers.



Me too. It's only the dash cluster though. Even the digital display isn't coming on. Very weird. Now I will say, that dash cluster does act up. Sometimes it doesn't come on immediately when you start the truck. Sometimes there's a 30-second delay. But I know that there are some issues with corrosion on the interior of the truck due to it sitting for so long and it having a ton of moisture in there.

Nothing that would've caused banging and grinding noises. Like I said, the initial event happened right as I shifted from 3 to D. And no, I didn't miss D and skip onto R or P.
Click to expand...
My money is on the flex plate or something around there
 
It is common enough for flex plate to crack. They make noise or get spotted when 4l60 gets 6 neutrals
 
Start easy, check the fuses and figure out the electrical issue. You must have lost power to something critical like the injectors or the whole PCM. My understanding is that you can drive these with the transmission completely unplugged (you only have R and 2, based on the manual valve), so if there's a short in the transmission, you could simply unplug it for troubleshooting. A good physical inspection may tell you what's going on. There is a small plug under the torque converter you can pull out and shine a flashlight up there, but you'll get a better view by pulling the starter.
 
I would try turning the engine manually with a ratchet. I would be curious if it lost a rod for some odd reason.
I have seen some SUVs of that era on marketplace with a bad knock, presumably a rod, is what one said.
Could have possibly damaged the crank position sensor and that's why it won't run.
Doesn't explain the electrical issues, however.
 
jonrpick said:
On a recommendation, I popped the driver's side valve cover off while a buddy bumped the starter.

Zero movement from the rockers. So at least I know they're good and tight.

/Sarcasm
Click to expand...
So looks like you wiped a cam?
Oh none move so what chain broke?
 
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