Gen I V8 Transmission Rattle?

[Broseph]

I've searched and even discussed this a little bit in Telco's "Engine Noise" thread, but no solution ever came up, and I'm having trouble narrowing the noise.

Other members including alex talked about a "rattle" when under load like getting on a highway or up hills.

I especially hear the rattle going up hills, I think the torque converter is supposed to fully lock when this happens because i can hear the rattle as soon as the RPM's drop going up a hill.

Some said cats, but it only happens the car drops to lower RPM's on hills, getting on highways etc. I've read around the net, some say coils, some say rear diff, some say throttle position, tire pressure....on and on.

It's a re-built 2002 3.9. I replaced transfluid, filter, and a new torque converter from american hot rod solutions and had it running since February 2012, with only 12,000 miles on the clock so far since the rebuild.

Question is, is this rattle a possible TC issue with only 12,000? And how can I check to verify if it is the TC? I've heard some say something about hitting the break pedal when it happens - something about a switch that makes the TC go into full lock. I did get under the car and knock the flywheel to see if it was cracked and it rang like no tomorrow so I'm guessing it's good

 

[joegr]

Actually, hitting the brake causes the TC to unlock, not lock.

 

[Broseph]

I'm guessing that would be one way to test it then. Are the TC's unlocking or locking when the rpms drop like I said going uphill? I get confused between the two, and when one is supposed to happen vs the other.

 

[55CrownVic]

To test TC for locking and unlocking, drive a steady 50 or 55 MPH (no cruise control). Hold steady on gas pedal and tap brake with left foot while watching tach. RPMs should climb a couple of hundred for a short time. This is when TC unlocks. When it locks back, RPMs should drop back.

 

[Broseph]

Okay, I get the unlock lock thing now, so it is locking when going up hill, it's not an issue with locking or not, it's just when it locks I'm getting noise (harder to tell cruising due to ambient noises and less load).

I'll try the break test to try to narrow down the possibilities. Is there something else I could be mistaking the sound for? The other day it was the worst I've heard it, I could hear a a faint noise coming from the firewall as well.

 

[Kumba]

Someone was telling me that the Gen1 V8 torque converter suffered from a noisy bearing in the clutch. It works fine but is noisy. You have to replace the torque converter to get rid of it. Not sure if that should be applicable since you already replaced the TC. I guess maybe if they rebuild a bad core and didn't replace the bearing or whatever it was.

But anyways, the TC unlocks when idling or under load. At a steady 2K-rpm cruise is should be locked. Is the noise constant or does it just pop up when accelerating or getting on/off the gas? Is it RPM-dependent I.E. happen only above 4500-RPM or does it happen everywhere?

 

[purevilpleasure]

What gas are you using?

Sure it's not pinging from predetination?

 

[Broseph]

Someone was telling me that the Gen1 V8 torque converter suffered from a noisy bearing in the clutch. It works fine but is noisy. You have to replace the torque converter to get rid of it. Not sure if that should be applicable since you already replaced the TC. I guess maybe if they rebuild a bad core and didn't replace the bearing or whatever it was.

But anyways, the TC unlocks when idling or under load. At a steady 2K-rpm cruise is should be locked. Is the noise constant or does it just pop up when accelerating or getting on/off the gas? Is it RPM-dependent I.E. happen only above 4500-RPM or does it happen everywhere?

It's most notable post acceleration on a hill - say going up, you give it gas and it will hit a lower gear, once you start "cruising" up the hill, the rpm's will drop and then the rattling starts happening. I have heard it under light acceleration, but mainly cruising.

Unfortunately, due to the exhaust system it's hard to hear in the upper rpm range, but I'd have to say no. Mainly lower rpm's right after the down shift.

 

[Broseph]

What gas are you using?

Sure it's not pinging from predetination?

93 always. Have a tune that's set at 93. Pinging I assume, typically happens in upper rpm's. She is solid in the upper rpm range.

I guess I could try taking the tune off, since I do have firm shifts set, and see how it works out.

A little more info on the trans: Currently running 2800 stall, transgo shift kit, and tune. After rebuiled, I had roughly 11 quarts of Valvoline Mercon V put in.

Thanks for the help guys. I just want to make sure I'm not grinding the tranmission to hell. After all the work, I'm a little tired of climbing under her - she's heavy.

 

[Kumba]

That sounds like detonation. Mine would do that right before it would puke a coil. Also did that when I got some bad gas in Maryland. To me it sounded almost like a baby rattle or BB's in a tin can. For me it only popped up under load, either chugging along at 30mph in 5th gear trying to gain a little speed or when you are getting on it.

The noise I heard while riding in a buddies LS with the bad TC bearing was what sounded like a groan. It reminded me of when you ride over the noise indents/strips on the shoulder of the interstate. You only heard it when the TC was unlocked and the bearing spun. He said it would work fine but just made noise. That noise was easy to duplicate because whenever you let on/off the gas you would hear the groaning noise. At a cruise or mild acceleration you hear nothing.

I would try going back to the stock tune and see if it goes away. You might have some mediocre gas or the 93-octane tune is too aggressive. Your engine could also be getting ready to puke a coil. I know that when mine developed the baby-rattle sound, which would start intermittent and get more consistent, it would eventually get the misfire and rough start/idle within a few weeks. It never stayed that way though, it always got worse.

 

[joegr]

... Pinging I assume, typically happens in upper rpm's. ...

Pinging normally happens at light to medium acceleration/load. I've not noticed it to ever correlate to engine RPM.

 

[Kumba]

Pinging normally happens at light to medium acceleration/load. I've not noticed it to ever correlate to engine RPM.

Yeah, the rattle I got was either from chugging along at low speed in 5th gear cause the transmission didn't want to downshift at 30mph, or when I was trying to pass someone without flooring it. In a drag race it never popped up. Was always in the mid-load range. Trying to push the car up a decent incline would cause that for me.

 

[Broseph]

That sounds like detonation. Mine would do that right before it would puke a coil. Also did that when I got some bad gas in Maryland. To me it sounded almost like a baby rattle or BB's in a tin can. For me it only popped up under load, either chugging along at 30mph in 5th gear trying to gain a little speed or when you are getting on it.

The noise I heard while riding in a buddies LS with the bad TC bearing was what sounded like a groan. It reminded me of when you ride over the noise indents/strips on the shoulder of the interstate. You only heard it when the TC was unlocked and the bearing spun. He said it would work fine but just made noise. That noise was easy to duplicate because whenever you let on/off the gas you would hear the groaning noise. At a cruise or mild acceleration you hear nothing.

I would try going back to the stock tune and see if it goes away. You might have some mediocre gas or the 93-octane tune is too aggressive. Your engine could also be getting ready to puke a coil. I know that when mine developed the baby-rattle sound, which would start intermittent and get more consistent, it would eventually get the misfire and rough start/idle within a few weeks. It never stayed that way though, it always got worse.

That would pretty much sum up what I'm hearing, albeit really loud bb's, but yes it would be under light load or when on a hill the car would drop into 5th or 4th.

It's strange that you say intermittent coil, since all the hundreds of threads seem to show symptoms when at WOT, and not hitting hills or giving it a little gas (i.e, coming off the on ramp).

I'll downgrade the tune, completely and see if it changes. My gas varies from different places so I doubt it is an issue.

I was going to say earlier, that it seemed like my acceleration hasn't been as good - the car didn't seem to have the uumph it did after the initial rebuild - but with no noticeable misfires at WOT and the sound limited to certain loads, I was attributing it to the torque converter since I read that acceleration can depreciate with TC failure.

Looks like accel coils are in my near future.

 

[LS4me]

Pinging normally happens at light to medium acceleration/load. I've not noticed it to ever correlate to engine RPM.

I get it when the loud pedal is on the floorboard and at the higher RPM.

 

[Broseph]

Yeah, the rattle I got was either from chugging along at low speed in 5th gear cause the transmission didn't want to downshift at 30mph, or when I was trying to pass someone without flooring it. In a drag race it never popped up. Was always in the mid-load range. Trying to push the car up a decent incline would cause that for me.

This is almost exactly when I have the rattle. I guess it's one of the other few cases maybe where a failing coil doesn't show up under hard acceleration or coming out of idle.

Here's to hoping this is the case for me since $200 in coils sure beats a $100 visit to a transmission shop to hear I need $2000 for a new transmission.

 

[joegr]

... I guess it's one of the other few cases maybe where a failing coil doesn't show up under hard acceleration or coming out of idle...

My experience has been that marginal coils are most detectable at light to med load. At idle and full acceleration, they often seem okay.

 

[Kumba]

I'd still try going back to the stock tune to see if it's just bad gas or an overly aggressive tune. That would or should cost nothing to test which is better then coils or a transmission.

 

[RigsLS]

My experience has been that marginal coils are most detectable at light to med load. At idle and full acceleration, they often seem okay.

I don't know about that joe, my #2 was failing and it would only flash P0302 misfire under WOT, was fine at idle or midrange.
Idling or just cruising around town like grandpa wasn't a problem, only gave me troubles during hard pulls.

 

[joegr]

I don't know about that joe, my #2 was failing and it would only flash P0302 misfire under WOT, was fine at idle or midrange.
Idling or just cruising around town like grandpa wasn't a problem, only gave me troubles during hard pulls.

You're experience if different than mine. That doesn't mean that either one is wrong. We could both be correct. It could be that coils fail in different ways, and it probably is.

 

[purevilpleasure]

I don't know about that joe, my #2 was failing and it would only flash P0302 misfire under WOT, was fine at idle or midrange.
Idling or just cruising around town like grandpa wasn't a problem, only gave me troubles during hard pulls.

Mine would act up every time but idle...only way I could get a code is WOT.

 

[RigsLS]

You're experience if different than mine. That doesn't mean that either one is wrong. We could both be correct. It could be that coils fail in different ways, and it probably is.

Not really a matter of right or wrong just different experience with failing marginal coils.
Didn't really notice any rattling or pinging though, just mostly motor bogging down.

Mine would act up every time but idle...only way I could get a code is WOT.

... they have their own failing characteristics it may seem.

 

[Broseph]

Not really a matter of right or wrong just different experience with failing marginal coils.
Didn't really notice any rattling or pinging though, just mostly motor bogging down.

This was the reason why I figured I'd ask to see what the issue is. Out of the numerous coil threads I've read, none of them seemed to say anything about rattling noises or pinging.

Since Kumba experienced rattling and I haven't had the same acceleration I had after getting the car running, I'm going with coils first. It's at least the cheaper option than a transmission shop visit.

But the rattling seems very odd.....anyone know what the possible correlation between coil and rattle is?

 

[RigsLS]

It's not a heat shield or aftermarket intake tube rattle sound ?

 

[Broseph]

Heat shield crossed my mind. I've been under it enough times to know that's not the case however.

 

[Kumba]

The pinging/detonation/mis-firing coil sounds like the rattle. It wasn't a heat shield and mine never threw codes unless the car was NOTICEABLY mis-firing, as in could barely drive it.