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Random rattling noise from bellhousing area

Chief915

Chief915

915A Maint Tech
Messages
406
Reaction score
1
Location
Cecilia, KY
I was out towing with the subruban last night, everything went great. On the way home I stopped at a traffic light and noticed an unusual "dull sounding rattling" noise coming from the firewall/floor/engine area. The noise only happens at idle speed, as soon as you touch the accelerator it goes away completely. All temps, oil pressure, power, smoke, etc stayed normal...the noise was the only thing new or out of the ordinary. No vibrations when it's rattling either, just the sound.

When I got home I let the truck idle and crawled underneath. From what I can tell, it seems to be coming from the bellhousing/inspection cover area. It sounds bad, not like rod knock bad, but worse than a loose piece of heat shield or something would. Plenty of clearence around the exhaust, it's not the heat shield above the starter rattling, etc. It has made this rattly noise once or twice in the past, and only lasted for a few minutes. Everything "looks" perfectly fine. No oil leaks, no loose parts, crank pulley spins nice and true, runs great, shifts great, etc. I went out this morning and started the truck, the noise was gone again. Dropped it in drive, reverse, park, revved it up, back into gear, etc and the noise still didn't come back.

For those of you that have heard one.. If you have ever listened to a big cam or small cam cummins idle and heard that rattly sound from the front of the engine? Thats basically what my suburban is sounding like.

I plan on pulling the inspection cover this evening after work to check torque converter bolts. I am headed 600 miles Saturday pulling a car, I really don't need any abnormal noises to go along lol.

Does anyone have other suggestions or had this happen to them?
 
I would have suggested the convertor or flywheel. Also check clearance between the downpipe and the frame. Look from under the truck and see if there is any sign it was rubbing.
 
Chief915 said:
I was out towing with the subruban last night, everything went great. On the way home I stopped at a traffic light and noticed an unusual "dull sounding rattling" noise coming from the firewall/floor/engine area. The noise only happens at idle speed, as soon as you touch the accelerator it goes away completely. All temps, oil pressure, power, smoke, etc stayed normal...the noise was the only thing new or out of the ordinary. No vibrations when it's rattling either, just the sound.

When I got home I let the truck idle and crawled underneath. From what I can tell, it seems to be coming from the bellhousing/inspection cover area. It sounds bad, not like rod knock bad, but worse than a loose piece of heat shield or something would. Plenty of clearence around the exhaust, it's not the heat shield above the starter rattling, etc. It has made this rattly noise once or twice in the past, and only lasted for a few minutes. Everything "looks" perfectly fine. No oil leaks, no loose parts, crank pulley spins nice and true, runs great, shifts great, etc. I went out this morning and started the truck, the noise was gone again. Dropped it in drive, reverse, park, revved it up, back into gear, etc and the noise still didn't come back.

For those of you that have heard one.. If you have ever listened to a big cam or small cam cummins idle and heard that rattly sound from the front of the engine? Thats basically what my suburban is sounding like.

I plan on pulling the inspection cover this evening after work to check torque converter bolts. I am headed 600 miles Saturday pulling a car, I really don't need any abnormal noises to go along lol.

Does anyone have other suggestions or had this happen to them?
Click to expand...

Pull the cover and check the convertor bolts....
 
GreatWhite said:
Pull the cover and check the convertor bolts....
Click to expand...

x3, Chief. You haven't lived 'till one or two of those have made ovals in your flexplate for you!
 
I'm on board with everyone else, -one more vote for converter bolts from me.......

When I bought my cherokee from a private party, it had loose torque converter bolts. The guy thought the engine was knocking (this was one of those times that I used my mechanical knowledge as an advantage and got it for dirt-cheap).

$600 and an hour later, I had the bolts tightened up and she was smooth as silk...

Loose flexplate/converter bolts make a nasty sound similar to a rod knock, but immediately go away as soon as you try to accelerate the mass.

Your flexplate could also be cracked as well, -certainly not unheard of on a 6.2/6.5.

My $1.25
 
Thanks for the suggestions.

I pulled the cover down tonight after work. Converter bolts are tight, nothing laying in the bottom of the inspection cover either. From what I could see everything in that area looked perfect. The noise didn't happen again all day.

I loaded up the wife's 2002 minivan and took it for about a 30 mile ride to see how my recently aquired 18' car trailer pulls. Everything went great, no noises or temp problems at all. We are taking off for Louisville tomorrow after work with this setup.

Even with the P-series chip under hard accel from a dead stop up to about 60 mph the EGT's only went to 525 post turbo. I know it isn't much of a test really, being that it's a fairly light load and it's pretty flat land around here, we'll see what happens when I hit the hills in TN and KY. :rolleyes5:

Kenny had me worried.... In one of his posts somewhere he mentioned that his "hot" tune from Heath would run the EGT's way up. Then again, maybe Bill didn't burn me the "hot" tune and gave me something a little more towing friendly. Oh well, I am happy with it no matter what it really is.
 
Acesneights1 said:
Also check clearance between the downpipe and the frame. Look from under the truck and see if there is any sign it was rubbing.
Click to expand...

I thought of that too... I have quite a bit of clearance all around the downpipe, enough to fit my fingers between it and the frame.

This noise kinda has me stumped. Everything seems fine, everything is tight, no signs of damage anywhere, no other problems or symptoms other than a weird rattling that came and disappeared out of the blue.
 
Man, after reading your post, I figured Kenny was spot-on with the downpipe rubbing -mine vibrates and makes all kinds of horrid noises when I'm backing up (my motor mounts were new when I did the rebuild 30k miles ago, but have been used and abused). :hihi:

Are you absolutely sure the noise isn't coming from the front end of the engine? Sometimes mechanical noises can be transmitted through heavy metal objects (blocks, crankshafts, etc.)

If there are no loose converter/flexplate bolts, then it is obviously something else....

Check your harmonic dampener to be sure the elastomer isn't cracked or aged. They can sometimes ratchet back and forth on the "limit pins" making a really bad sound.

I'm going out on a limb here, but it can't hurt to check......
 
My exh. tube between the down pipe and the muffler was just touching the front hanger, it vibrated like crazy.
 
I put a new 6.2 in for a guy that had a rod knocking and a month later the flex plate broke. I still have the engine because I didn't think it was a rod but never have pulled it apart to check the bottom end. Flex plate looked fine when I had it out.
 
Fuel lines on the driver side of the engine can wedge between the floor pan and engine. Check to see if they came out of the plastic in the metal hold down. hoses for PS or engine oil can also rattle.
 
Chief915 said:
Thanks for the suggestions.

I pulled the cover down tonight after work. Converter bolts are tight, nothing laying in the bottom of the inspection cover either. From what I could see everything in that area looked perfect. The noise didn't happen again all day.

I loaded up the wife's 2002 minivan and took it for about a 30 mile ride to see how my recently aquired 18' car trailer pulls. Everything went great, no noises or temp problems at all. We are taking off for Louisville tomorrow after work with this setup.

Even with the P-series chip under hard accel from a dead stop up to about 60 mph the EGT's only went to 525 post turbo. I know it isn't much of a test really, being that it's a fairly light load and it's pretty flat land around here, we'll see what happens when I hit the hills in TN and KY. :rolleyes5:

Kenny had me worried.... In one of his posts somewhere he mentioned that his "hot" tune from Heath would run the EGT's way up. Then again, maybe Bill didn't burn me the "hot" tune and gave me something a little more towing friendly. Oh well, I am happy with it no matter what it really is.
Click to expand...

It was a misunderstanding as to what I wanted. I sent him my ecm and he tuned it personally. After the egt problem we talked extensively about it. He offered to retune it but I never had the chance to lay it up and aside from high egts towing, I really liked the way it drove. The truck ran like a bat out of hell so I kinda just lived with it and drove it by the pyro. Also he had said he could have cut it back through tuning or I could cut it back by removing certain lead like material from my right foot.....:hihi:
Just want to clarify that I think his tunes are the best and my issue was merely the wrong tune for what i was doing. I never had a towing tune. I was supposed to check the timing and fuel rates for Buddy but I could never get that part of car code to work. I think I got a bum copy of it or something.
 
I used to get occasional rattles from the ex hitting the crossmember as well when I put the 4 inch on. It was a tight squeeze on my tahoe but I had cat back 4 inch.
 
Just got back from the trip. 1,240 miles round trip from Savannah, GA to Louisville, KY and back pulling a 22' car trailer loaded with a 2002 Chrysler mini van.

Everything went absolutely awesome, no issues at all. Temp guage pointed at 210 twice for about 15 seconds each time during the trip, then the roar of the fan started and it dropped right back down to normal and stayed there.

The longest pull of the trip was in southern TN, on TN-111, is a 8% grade and 4 miles long. I had the cruise set on 65 at the bottom and the converter locked, max EGT on the hill was 850, post turbo, and happened near the top of the hill. It pulled the hill much better than I was expecting really, but did slow down to about 40 by the top of the hill, that was at the 850 EGT point and I have a feeling the IAT was high at that point too. Believe it or not, coolant temp stayed the width of the needle below 210 and never moved while pulling this hill, which was a very plesant surprise. The fan was engaged and roaring the whole way up, in other words doing it's job perfectly.

All in all, I am very happy with the way it ran/pulled during the trip. It maintained whatever speed I had the cruise set to, normally 70-75 mph, the entire way and really impressed me.

The noise never reared it's ugly head again either. :D
 
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