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knocking when slowing down???
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Post Fiend
Joined: Aug 2006
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From: Yorkton Sask
knocking when slowing down???
howdy dudes,
wondering if this rings a bell with anybody, taking the foot off the gas to slow down, a hollow knocking sound occurs, only when "de-celerating" its fairly rapid but decreases as the truck slows. lug nuts are tight...brakes are good...i'm stumped...anyone???
'96 f150, 4.9 l6, e4od
wondering if this rings a bell with anybody, taking the foot off the gas to slow down, a hollow knocking sound occurs, only when "de-celerating" its fairly rapid but decreases as the truck slows. lug nuts are tight...brakes are good...i'm stumped...anyone???
'96 f150, 4.9 l6, e4od
Posting Guru
Joined: Jan 2006
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From: The dark carnival
Does it sound like it is coming from inside the motor or the exhaust??
I had an odd sound when I let my foot off the gas and it due to my exhaust (headers, dual, no cats, glasspacks). The unburned fuel was actually igniting in my exhaust system. Particularly when I let off the gas pedel because the unburned gas that goes out the exhaust valve is moving slowly and the heat of the pipe itself lights the gas.
I had an odd sound when I let my foot off the gas and it due to my exhaust (headers, dual, no cats, glasspacks). The unburned fuel was actually igniting in my exhaust system. Particularly when I let off the gas pedel because the unburned gas that goes out the exhaust valve is moving slowly and the heat of the pipe itself lights the gas.
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Joined: Jul 2006
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I've worked on many a car and truck. Some peoples idea of an oil change is adding a quart or two when low.
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Post Fiend
Joined: Aug 2006
Posts: 20,099
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From: Yorkton Sask
its fairly evenly spaced knocking, faster first as you start to slow, then slows as you do...almost like a spoke flapper...if ya had only 5 spokes...oil changes every 4-5000kms for me...
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From: West Mansfield, Ohio
Hmmm... so we know it's probably not engine related. Do me a favor and go take er for a spin. When you go to slow down, pop it into nuetral. This will allow the engine to come down to an idle. See if the noise differs from when you keep it in drive while slowing down.
If that is still the same, do the test again but this time instead of putting it into nuetral, push the OD button on the end of your shifter to downshift out of overdrive (if you're going around 50 or 55 at first.) See if the noise differs. If you are going about 30 or 35, pull the shifter down into 2nd and see if it still does the same noise in the same pattern. Make sure to wear your seatbelt when you do this... I'd hate to see ya get thrown through the windshield.
I think we know for sure that if the rear differential is turning the driveshaft/guts of the tranny, rather than the guts of the tranny turning the driveshaft/rear diff, that is when we're getting the noise. Sound logical?
If that is still the same, do the test again but this time instead of putting it into nuetral, push the OD button on the end of your shifter to downshift out of overdrive (if you're going around 50 or 55 at first.) See if the noise differs. If you are going about 30 or 35, pull the shifter down into 2nd and see if it still does the same noise in the same pattern. Make sure to wear your seatbelt when you do this... I'd hate to see ya get thrown through the windshield.
I think we know for sure that if the rear differential is turning the driveshaft/guts of the tranny, rather than the guts of the tranny turning the driveshaft/rear diff, that is when we're getting the noise. Sound logical?
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Post Fiend
Joined: Aug 2006
Posts: 20,099
Likes: 7
From: Yorkton Sask
lol...not a u joint...changed them about a year ago, put in the best i could find.
i have done the od button option...still the same...what are we getting at by proving which is driving?? (hope that don't sound rude...) ummm...its the shaft/diff turning the tranny i'm pretty sure...next?
sherm
i have done the od button option...still the same...what are we getting at by proving which is driving?? (hope that don't sound rude...) ummm...its the shaft/diff turning the tranny i'm pretty sure...next?
sherm
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Post Fiend
Joined: Aug 2006
Posts: 20,099
Likes: 7
From: Yorkton Sask
maybe rear bearings for me...its 2wd...can't see the front causing that type of noise...got a couple of ball joints needing replaced, upper&lower drivers, upper passenger. could that do it??
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Joined: Jul 2005
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Ball joints make a loud thump, you also feel it. Sure fire way to fix it is the lift the truck up and see if the wheel wiggles, up and down. Then need to be replaced. It could also be your tires out of balance and they hit that certain point and make the ball joint knock.
Make sure all your bushings in the front are still good too.
Make sure all your bushings in the front are still good too.