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1989 Ford 460 knocking

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Old 04-14-2018, 11:45 AM
1989FordF250
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1989 Ford 460 knocking

Hello All, I have a 1989 Ford F250 with a 460 and C6 auto. I noticed a knocking from the engine last fall but I didn't try to do anything about it since I don't drive the truck in the winter. Now with the weather getting nicer, I am wanting to figure out what this knocking is. I listened to the bottom end with a stethoscope and thought the knocking was louder near the bell housing but I'm not 100% sure. I torqued the torque converter nuts to 25 ft. lbs. and I'm sure its not loose. The motor only has 138k on it and judging from how clean the valves are(they are still shiny and there wasn't hardly any sludge up in there) compared to some neglected engines I have seen so I can't really Imagine that is a rod or main bearing but I don't want to end up with a rod thru the block or a seized engine. I am leaning towards the flexplate but I don't want to go buying parts or yanking the whole tranny if it isn't even the flexplate. Is there any way to confirm this? I took a video so I will post it on youtube and put the link up once its uploaded. Your help and suggestions are appreciated!
 
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Old 04-14-2018, 04:57 PM
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Did not yet look into a manual, but there should be a section on running down this symptom.

For now, shorting each cylinder one at a time by removing plug wires, should isolate a knock to a particular cylinder, and the inspection plate on the transmission can be removed, and the engine turned with a breaker bar on damper bolt, checking for cracks, loose nuts, etc.
 
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Old 04-14-2018, 05:32 PM
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this is one of many things that is just a pain in the *** to deal with over the internet....you must also define "knock" so that we are on the same page. lifters tap, exhaust leaks tick, rod bearings knock. We need to be sure what it is you are hearing and rule out the others in order to accurately give advice.

Also, is it a knock that is changes with rpm? Is it constant or intermittent?
 
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Old 04-14-2018, 07:53 PM
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The knock seems to diminish with RPM and it is only heard at idle. It seems to go away if you give the truck some gas. As you can see, we aren't dealing with a lifter knock, or exhaust leak. It is definitely something in the lower end. Here is the video of the truck knocking. Take a listen and see what you guys think.
 
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Old 04-14-2018, 09:42 PM
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Sounds trans related to me, seems too random to be a rod knock. Best to test oil pressure, if that's good then id suspect cracked flex plate or something of the sort. Does it drive ok?
 
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Old 04-16-2018, 09:09 AM
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Originally Posted by '89F2urd View Post
Sounds trans related to me, seems too random to be a rod knock. Best to test oil pressure, if that's good then id suspect cracked flex plate or something of the sort. Does it drive ok?
Yes it drives just fine, engine purrs and you don't hear any hammering like rods would do on an accelerating engine. I will get an analog oil pressure gauge and hook it up. I was wanting an oil pressure gauge anyways. So, since it is really looking like I'm going to have to drop the trans, what do I need to do in means of support for the engine? I have low lift trans jack but also have access to a 2 post lift and a high jack. The ease of doing it over head would be nice but I know the trans doesn't even need to come out all the way. Either way, I just don't want to end up having to replace motor mounts or having something else break. Thanks for your help!
 
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