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2003 Chevrolet Silverado 4.8L.
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Discussion Starter · #1 ·
When I start my truck and idle it has a knocking sound in park and I put it in gear it speeds up the noise beats the faster I go almost sounds like a sewing machine from the cab but it was doing that before and quit now it’s back again and I thought it was the torque converter but I’m not sure what a bad one does for sure any ideas would sure help I can’t afford it to take it to a shop I have to DIY it ! Thanks for your time !! Dbrest
 

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Any chance you have a broken exhaust manifold bolt or two? Fairly common.
 

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2003 Chevrolet Silverado 4.8L.
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11 Posts
Discussion Starter · #3 ·
Any chance you have a broken exhaust manifold bolt or two? Fairly common.
Not appearing to be I’m getting a second set of eyeballs on this I’m going to go ahead and change transmission fluid and filter as well as putting a new starter on it if that starter bindex isn’t coming out all the way and engaged directly would cause some trouble I think but not for sure but it’s a weak starter and I need a new one anyway but that’s what my plan is so far unless I hear anything better soon I’m all ears and I have an open mind
 

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2003 Chevrolet Silverado 4.8L.
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11 Posts
Discussion Starter · #4 ·
Not appearing to be I’m getting a second set of eyeballs on this I’m going to go ahead and change transmission fluid and filter as well as putting a new starter on it if that starter bindex isn’t coming out all the way and engaged directly would cause some trouble I think but not for sure but it’s a weak starter and I need a new one anyway but that’s what my plan is so far unless I hear anything better soon I’m all ears and I have an open mind
And yes will definitely look for exhaust manifold broken bolts as well
 

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2003 Chevrolet Silverado 4.8L.
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Discussion Starter · #6 ·
We had a truck at work that made a similar noise and it sounded like the engine. Turned out to be a cracked flex plate. When they showed it to use, the crack was not easy to see.
Thank you for the heads up and I had someone mention it to me and I have no idea what to look for as far as do I need to put it in infrared light like die check or something? Or the naked eye will catch it ?
 

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2021 GMC Sierra Denali CC 4WD Ultimate 6.2L
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Naked eye, you could remove starter to look for any cracks but might not help. As I recall the cracks in that work truck were around the bolt holes where it mounted on the crankshaft. We took the truck to a GM dealer because it was a fleet truck (state owned). That would have to be the last resort to pull the trans to check. An experienced mechanic might know some tricks to determine if he flexplate is the problem?
Typical GM flexplate
 

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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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You probably could unbolt the torque convertor from the flexplate and push it into the transmission a bit, and use an inspection camera to get in there to see.
 

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2003 Chevrolet Silverado 4.8L.
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11 Posts
Discussion Starter · #10 ·
Naked eye, you could remove starter to look for any cracks but might not help. As I recall the cracks in that work truck were around the bolt holes where it mounted on the crankshaft. We took the truck to a GM dealer because it was a fleet truck (state owned). That would have to be the last resort to pull the trans to check. An experienced mechanic might know some tricks to determine if he flexplate is the problem?
Typical GM flexplate
Thank you so much for your kindness and patience with your advice and I’m going to keep it parked and tear it down pulling the transmission and going to start inspecting everything and replacing what’s broken and repairing it until all has been accounted for so I can eliminate the possibilities if anything once it’s back together and hopefully I will have it fixed by the grace of God it won’t make that noise again but it’s causing it to misfire I found two exhaust manifold bolts broken off and I’m going to keep going and I’ll fill everyone in on part 2 03 Silverado 1500 complete undercarriage inspection and transmission maintenance and inspection because I’m going to change fluid and filter out and clean it up and I’m Changing the carrier bearing while I’m at it thank you talk to ya soon
 
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