2001LC
SILVER Star
Stop at Harbor Freight, buy a stethoscope on way home you'll love it a mechanics best friend. Try old piece of carpet or cardboard on that cold garage floor, really helps
Uh-oh! Ominous knocking sound from front end - advice? (1 Viewer)
- Thread starter buddysharp
- Start date
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I would look at everything first, but I think you have a broken flexplate. It's a job to replace. Transmission will have to come out. It's hard to tell from the video, but listen to these...... you'll know the sound better than anyone.
http://www.youtube.com/watch?v=TrERUbjhnSM
http://www.youtube.com/watch?v=l4frOEtW7Ds
http://www.youtube.com/watch?v=TrERUbjhnSM
http://www.youtube.com/watch?v=l4frOEtW7Ds
- Thread starter
- #23
flushed everything BUT the power steering pump. did flush the front t case as well as replaced boot clamps due to leaking grease.
This is so damn random. Can't diagnose it when it doesn't happen.
The flex plate sound sounds spot on although maybe louder - we were in the cabin and couldn't get out in traffic to open the hood. And it was the first time I've heard it - but if flexplate is broken, would that only be intermittent?
This is so damn random. Can't diagnose it when it doesn't happen.
The flex plate sound sounds spot on although maybe louder - we were in the cabin and couldn't get out in traffic to open the hood. And it was the first time I've heard it - but if flexplate is broken, would that only be intermittent?
2001LC
SILVER Star
Sound like pump hopefully not in transmission. If this happen most often when foot on brake, it points to brake booster pump motor first or accumulator. Check all fluids under hood, including coolant. Have you seen any leaks or have any fluid needed topping off?
Have no idea why you say T-case payfly, if sound mainly while stopped.
If you don't have stethoscope use a long screwdriver as one, listen for any off sound; pulse, oscillating, chirp etc...
Press brake peddle until pump comes on and off four or five times, do while in gear at idle.
Oh and so know one get upset with "always assume" safety issues, please don't put pointy end in ear.
Have no idea why you say T-case payfly, if sound mainly while stopped.
If you don't have stethoscope use a long screwdriver as one, listen for any off sound; pulse, oscillating, chirp etc...
Press brake peddle until pump comes on and off four or five times, do while in gear at idle.
Oh and so know one get upset with "always assume" safety issues, please don't put pointy end in ear.
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Yes. Because its probably only cracked. When you're in gear, on the brake, there is pressure on the plate. Sometimes it will shimmy and smack, thats the knock you hear. Very common for it to be intermittent until it breaks apart. (That's not good)
The other slight possibility is your starter not disengaging.
I think trans related is on track. The noise is just horrible and if it was engine internals it would persist and you'd be looking for a new motor by now. That plus the fact that it's gear selector dependent and drive train state dependent makes me think trans as well. I also think trans because the automatic trans is the most unfamiliar assembly to me so I naturally like to blame it first. I would show that vid to a trans guru and see what they think.
As for safety warnings, I like to avoid guilt or liability by using a strong disclaimer like: Following any of my advice will likely lead to your death and the death of a thousand innocents.
Trunk Monkey
Moderator
It stopping once you've kicked out of gear leads me to think drivetrain too and not something vibrating against something else. Agree with pafly on hopping out while it's doing it and localizing where it's coming from. Alternative to looking like you're playing doctor with your car you can use a long screwdriver as a stethoscope, put the blade on the object and your ear on the handle end, works great. Just be careful about the moving belts.
Although dangerous, if you can get someone you trust in the drivers seat and can reproduce the sound in an empty parking lot, you can crawl underneath while the sound is happening and try to pinpoint it better. I think you'll find it from underneath and not on top of the engine. I'm still guessing its a broken flexplate, but the fact that it stops so suddenly when taken out of gear is puzzling. Maybe another video is in order from underneath?
In any case, please let us know what you find or what is diagnosed at a shop.
In any case, please let us know what you find or what is diagnosed at a shop.
Wow, I agree about checking everything else first. Would this be the first reported cracked flex plate on a 100 series on Mud?
I just wanted to 
and tell you to be CAREFUL! Oh yeah, and always DRIVE FAST AND TAKE CHANCES!
disclaimer:
LX101North takes absolutely no responsibility in the second sentence of this post. What you do with this information is solely the responsibility of yourself. Understanding that your vehicle weighs 7000 pounds and if your vehicle met you in a parking lot while you were laying down taking a nap, you would most definitely be mistaken for a speed bump. LX101North would also like to clear his conscious by telling you, "Do not get all of this information in your head, and some how get it all misconstrued only to end up in an empty parking lot somewhere, laying on the ground, with a giant screwdriver pressed to your ear, and giving your buddy the thumbs up to drive over you".
and tell you to be CAREFUL! Oh yeah, and always DRIVE FAST AND TAKE CHANCES!disclaimer:
LX101North takes absolutely no responsibility in the second sentence of this post. What you do with this information is solely the responsibility of yourself. Understanding that your vehicle weighs 7000 pounds and if your vehicle met you in a parking lot while you were laying down taking a nap, you would most definitely be mistaken for a speed bump. LX101North would also like to clear his conscious by telling you, "Do not get all of this information in your head, and some how get it all misconstrued only to end up in an empty parking lot somewhere, laying on the ground, with a giant screwdriver pressed to your ear, and giving your buddy the thumbs up to drive over you".
2001LC
SILVER Star
^ May I add; If all else fails, have a cup of ATF fluid sweeten with coolant, an just chill.
Feels like transmission to me. I was wondering if it was the torque converter, or front bushing, or loose converter bolts in the tranny. Flexplate seems like a good prognosis. I agree with the stethoscope. You can also use a long metal rod/bar/screwdriver. Touch one end to the item in question and push the other end against your temple. Don't do this near rotating parts!
Good Luck,
G
Good Luck,
G
^ May I add; If all else fails, have a cup of ATF fluid sweeten with coolant, an just chill.
Damn that sounds good! Is it happy hour yet?!
- Thread starter
- #36
Ok, so the noise has only returned once, of course I wasn't in the LC. I've checked motor mounts, fan and shroud, exhaust clearance, put a stethoscope on the front diff while running and in gear, out of gear and generally every other dang scenario I could think of. NADA. Can't figure out how to reproduce. Did I use the word INTERMITTENT and the other word SCARY. It's not a vibration. It's not a fan shroud. It's something inside the front tranny or diff with metal slapping metal. And it's INTERMITTENT. It only happens in gear, rolled to a stop. It disappears if you take 'er out of gear, it re-appears in when you put back in gear, and then mysteriously disappears again. I drove 40 miles this evening trying to get it to happen again. Nada, Nothing.
I'm going to drink the ATF with a shot of schnapps and pass out.
I'm going to drink the ATF with a shot of schnapps and pass out.
- Thread starter
- #37
Thanks for all the suggestions. I really appreciate it. I'm going to try again tomorrow and see if I can break it for good as the wife doesn't want to drive the LC for fear it will implode with a half dozen kids rolling down the highway.
If its a cracked flexplate or the torque converter bolts are loose, you could save yourself a heap of cash by diagnosing that prior to just driving it til it breaks. The collateral damage could really add up the costs quickly.
Can you tell from the FSM (or by crawling under) if there is an inspection cover that's easily removed? You might be able to reach up and check the bolts or see a broken flexplate.
Trade it in!!
semlin
curmudgeon
do you feel anything in the steering wheel when the noise occurs? the fact it happens only in gear and only when at rest makes me think driveline easpecially ujoints. the problem may be loose bearings that disappears when under full load. it also might be a rotted bushing in the steering causing metal on metal.
u-joints can be hard to isolate. i would check all four driveshaft ends for play (back and forth and up and down) and also observe all your steering links looking for play while someturns the wheel rapidly back and forth.
edit: i guess it might be play in the steering rack also.
u-joints can be hard to isolate. i would check all four driveshaft ends for play (back and forth and up and down) and also observe all your steering links looking for play while someturns the wheel rapidly back and forth.
edit: i guess it might be play in the steering rack also.
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