Alarming rattle can noise from under truck

[Scott6]

Yea I got nothing. I finally got my wife to help out but while under the truck with the noise happening I still can’t tell. I sounds like it’s coming directly from where the trans meets the engine. But the stethoscope doesn’t hear the noise when touching various parts. I was able to better hear that it is not the cat. (bummer)

At this point I think I’m going to prep for the truck to be down a week or two. I’ll first pull the exhaust pipes to get them out of the way. I can run it for a few mins open turbo to be super sure it’s not the cat. Then pull the starter and inspect, then back the trans off the engine and inspect. If anything I can fix the leaking rear main seal so it won’t be a total loss. I’m also due for an oil change so the timing is perfect there. Wish me luck lol

If it is the flex plate, it might be time for a upgraded converter and flex plate while it off. Idk that’s a lot of cash.

 

[DavidC]

Just a guess, anybody know what the TC sounds like when going south ?.

 

[Ozymandias]

I dont think it is in the area of the converter, it would do it in every gear then. But who knows..

 

[Scott6]

I dont think it is in the area of the converter, it would do it in every gear then. But who knows..

Yea I’m a little worried it’s the torque converter, idk how to tell yet. The truck has always had this little low speed surge or pulse when putting around in parking lots, always thought that was the TC too.

but like said above, a tc would do it in all gears right?

 

[Killer223]

my 08 did same damn thing took me for bloody ever to find it.
mine was the heat shield on the fuel tank. rattling against it's self., it's almost a two layer design. i felt and grabbed all of them, all were tight. so i thought it wasn't it.
then i attached a gopro under the truck and drive it. watched the heatshields move with the vibration of the engine.
that my vote.

 

[brucejohnson]

Yea I’m a little worried it’s the torque converter, idk how to tell yet. The truck has always had this little low speed surge or pulse when putting around in parking lots, always thought that was the TC too.

but like said above, a tc would do it in all gears right?

That's the thing that "seems" to eliminate a lot of possibilities.
No barbed wire wrapped up on the driveline. (directional cause, but driveline moving slower than rattle noises, which seem to be closely related to RPM)
Something loose in/on engine (Not directional so probably not)
Loose exhaust internals (directional effects possible; exhaust flow emulating RPM for rattling effects)
Shift linkage position. Too rattley???...(mine had the nylon bushings worn and caused a nasty, annoying squeak that dealer could not locate. I thought it was side steps or body mounts. Changed, no fix.... I found the cause several years later).
Transmission - Torque converter - bell housing area: (all have thick cases and/or fluids that would dampen tinny sounds; and should be noticed in both forward and reverse, so probably not).

 

[Scott6]

Yea, seems like a converter issue would do it in reverser too for sure. same with flex plate actually.

I’m wondering, would clogged up trans filters hold back enough fluid to make the tc act up? (Again, why not reverse) I did see the trans gauge randomly spike 160-230-160-230. I read from the hot line out so it generally responds fast.

 

[Scott6]

Drove around a bit jus now. Didn’t make the noise at all during acceleration this time, WTH? However I did hear it when deceleration, EB on or off did seem to matter, almost like it was making it when the converter was locked then stocked when it unlocked. Also, it did seem like it was not unlocking the converter right away when I let my foot off the gas. It it is like 40* out and it always shifts a little different when cold.

 

[Scott6]

I hooked up my 5th wheel today, I had to go get it registered in TX so I can sell it. I drove the truck around to get it warm first and noise stoped in under 30 seconds. Once it was to operating temps I kinda gave it the beans with the 5er and the truck didn’t even blink, like nothing is wrong. I have no idea, I’m gonna keep hunting for rattling parts. I’m also going to do my overdue oil change, fuel filter and a pan drop trans service. We’ll see if I ever figure out the noise or the trucks stop running on me lol. I’ll post back if I find out anything new.

 

[EDankievitch]

Reading your thread made me think way back in 1990 the flexplate on my 89 cracked. It started making noises when cold shen first put in gear. Forward reverse didn’t matter. The noise would go away as soon as you’d give it the slightest bit of throttle. It slowly got louder and more frequent until it made noise when ever you would stop in gear . It ended up taking out the toque converter and the pump on the transmission. Warranty took care of it all the new flexplate was a totally different design. Never had an issue again. The cracks didn’t really show until the whole thing was out of the truck.

 

[Scott6]

Yea I’m thinking I’m gonna pull the trans back and inspect next weekend. I need to pickup a trans jack from harbor freight sometime this week.

There’s nothing I can to to inspect the converter is there? Can I swap the converter without taking the trans too far out? Like if I back it off and lower it from the truck? Can I pull that out while I’m down there?

 

[Ozymandias]

I dont think so, you have to pull it, the converter itself weighs 60lbs.
I always take of the Transfercase and afterwards the transmission.
Be carefull with the converter that it is really fully seated into the pump. Otherwise $$$$.

All in all its not a bad job, the engine stays on its place by the exhaust holding it balanced on the engine mounts.

 

[Scott6]

I dont think so, you have to pull it, the converter itself weighs 60lbs.
I always take of the Transfercase and afterwards the transmission.
Be carefull with the converter that it is really fully seated into the pump. Otherwise $$$$.

All in all its not a bad job, the engine stays on its place by the exhaust holding it balanced on the engine mounts.

sounds good thanks. I’ll probably leave the converter alone. I’m due for new trans fluid anyways so pulling the transfer case first isn’t an issue, not trying to save fluid here. At this point I’m kinda hoping the flex plate is cracked, I can just swap it, fix my years old rear main seal leak and call it good. Getting sick of dealing with it, and only getting a a few min of troubleshooting before it stops.

 

[Scott6]

I dont think so, you have to pull it, the converter itself weighs 60lbs.
I always take of the Transfercase and afterwards the transmission.
Be carefull with the converter that it is really fully seated into the pump. Otherwise $$$$.

All in all its not a bad job, the engine stays on its place by the exhaust holding it balanced on the engine mounts.

So doing some measuring, Im thinking I can put the truck on 4x jack stands at the axels. then lower the trans off with a trans floor jack. it might not be high enough to get the trans out from under the truck, but I should be able to slide the converter on and off. I have been watching some videos, it honestly doesn't look that hard at all, just line it up so the pump tabs connect and the converter fits in there flush. Thats if I do determine the converter to be the culprit. Do you need to relearn or quick lear with just a new converter?


EDIT: I figured out I do not need to quick learn if I just swap the converter. I wouldn't mind an upgrade anyway, so it might be worth a shot. Converter, better flex plate since im in there, new rear main.. hmmm..

 

[DavidC]

Stumbled across this.
Your torque converter can make a variety of noises when it goes bad. You may first notice a whine, similar to a power-steering pump that is low on fluid. The stator within the assembly uses an overrun mechanism with a series of clutches that, when bad, can cause a rattling noise.

 

[Scott6]

Stumbled across this.
Your torque converter can make a variety of noises when it goes bad. You may first notice a whine, similar to a power-steering pump that is low on fluid. The stator within the assembly uses an overrun mechanism with a series of clutches that, when bad, can cause a rattling noise.

Yea I think I read that same thing too. The sound sure does sound like its coming from the bell housing. Weird because the stethoscope doesn't pick it up really anywhere, but my ears hears it dead on the Bell. If its coming from inside the converter. that might make sense why the noise vibrations are not making it the trans housing and thus to the stethoscope. Also, the random temp trans temp spike I saw once time sould have been something weird in the converter since it pumps right form there out the cooler line where I read temp from. ugh... Maybe I do just buck up and take it to a shop. I just wish I had one I could trust.

Or I just pull it myself, use the cost savings to upgrade the flex plate and but a trans jack... hmmmm...

anyone know a good shop San Antonia area haha?

 

[sag2]

If you think it might be the flex plate and don't want to pull the trans, get a couple pieces of threaded stock, or get a couple longer trans bolts and cut off the heads. Cut a screwdriver slot in one end and use them as pilot bolts to keep the trans lined up as you slide it back on the jack far enough to inspect the flex plate. They also come in handy when reinstalling the trans but you might need to cut them a bit shorter for that.
If your pulling the trans and want to make sure the converter is seated all the way in the pump, measure it before you pull the trans so you can be sure it is all the way in before trying to re-install the trans.

 

[Scott6]

So is that the hardest part, lining it up after? I have not done it, before but it’s not something I’m really scared of. I would be buying the nicer 800# trans jack from HF for the job. Seems easy enough

remove everything, slide off the old TC, fill and slide in the new one, bolt it all up. Use torque spec on new flex plate.

 

[AEdelheit]

If it was my truck I would contact Randys transmissions as they have the 68RFEs down really well and have a full DIY kit if you want to upgrade some parts while you are in there.

 

[Scott6]

Things got a little crazy here haha.. refocusing here and another question. Im leaning on the converter. The sound is defiantly coming form the Bell housing area, the flex plate bolts look good. However the sound and triggers just do not line up with a cracked flex plate. I am feeling some funny lockup delays now, but it could be in my head. Now i'm wondering if the pump is actually giving me greif. Like when the fluid is cold its not feeding the converter properly. So noise in the converter due to the pump. For the price of a trans shop I could swap both the converter and the pump, maybe that is the way.

The fluid is Pink, smells sweet, no metal form what I can see. I did pickup new filters they will be here Thursday. Im considering a hail-marry pan drop and filter change but let's be honest, its not gonna help anything.

I love doing stuff myself, learning and diagnosing problems. But IDK, this is getting out there. Guessing on $900 parts is not cool.