# Uh, Oh, here we go.....



## White Gardens (Oct 29, 2008)

Let's start off with a little background on my truck.

01, C3500 with an 8.1, 4l80e transmission.

I bought the truck from the local college as they were at the ten year cycle with the truck and they were replacing it. When I bought the truck, I was told that the transmission was replaced a little over a year ago. Basically about 6 months before I got the truck.

When I drove it home I noticed a funny noise and have been living with it. It makes a whining noise similar to a hydraulic whine of a hydraulic pump or motor. Took it to a tranny shop and they believed that one of the output gears has a chipped tooth, causing the noise. They said it wasn't fatal, but was just going to be annoying. It's just noisy enough that I turn the radio up and not notice it.

Now, flash forward to the present. Just yesterday I noticed a new noise. In Park/Neutral, I'm getting a slight knocking, consistent noise that is associated with the engine speed. It started yesterday from what I could tell. At first I though it was the motor, but my oil pressure is still reading good at idle (25-30). Listening it sounded like it was coming from the back of the motor, bell housing, or transmission.

When I put it in any gear, the noise goes away, it kinda winds up (the noise) and disappears. When I shift between forward to reverse, I hear it slightly and then goes away.

I'm wondering if it's the flexplate or the converter. I'm going to drop the inspection cover today to see if there is any loose bolts on the converter and just to take a look. I don't think I have time to split the tranny and thoroughly check the flexplate though.

Also, one other thing. My dome light isn't working correctly right now either. It intermittently works with the headlight switch and the two push button lights on it don't work either. Here is the kicker, my dome light flashes quickly when I shift from Reverse to Drive. The only reason I bring it up in this situation is that I'm wondering if I'm getting an electrical gremlin messing with the torque converter.

That's it guys. If anyone has experienced this problem before, let me know. I'm getting ready to call some mechanics to see if they have experienced these issues or not before I decide to replace anything.

Thanks in advance,

Nick


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## NICHOLS LANDSCA (Sep 15, 2007)

You could check all the grounds, good luck


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## White Gardens (Oct 29, 2008)

I'm also going to check my Cat converter too to see if it's rattling. We'll see, I'll keep you guys informed as to what's going on.


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## MarkEagleUSA (Nov 27, 2005)

White Gardens;1206466 said:


> It makes a whining noise similar to a hydraulic whine of a hydraulic pump or motor.


The 4L80E on my 97 2500 with 153,000 had a similar sound when I brought it home back in August. I added some Sea Foam Trans Tune for about 40 miles, dropped the pan and changed the filter and fluid. The whine went away and the transmission started shifting much smoother immediately.


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## zzamud (Dec 23, 2010)

Just changed out a flexplate on a 01 k2500 on monday. Customer heard a starter whine. I found the center of the flexplate( 8 bolts) completely ripped out of the flexplate.


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## thesnowman269 (Nov 7, 2009)

the bolts on your torq covertor are loose. take the inspection plate off and torq them down.


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## sweetk30 (Sep 3, 2006)

4l80-e have a big whine shound to them also.

but ya you got other problems to. like said start basic. check flex plate and convortor bolts. 

if you cant see the flex plate see if a shop close to you has one of those scopes with the cammera/screen . can wiggle that up in easy and see.


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## White Gardens (Oct 29, 2008)

The whine associated with the tranny is definitively different than the normal whine that these produce. My mechanic originally said the same thing until he got in it and heard it himself.

Here is a vid of the current noise. It's gotten louder, and I am now noticing it in Drive.

I did check the converter bolts after taking the cover off and they were all tight. In the vid I revved it a couple of times and you can hear it subside a bit.


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## sweetk30 (Sep 3, 2006)

do us a favor if you will. remove the convortor bolts. slide the convortor back to the tranny. then fire up the motor. easy test to eliminate motor or tranny problem. 

and a cracked but not fully broken flex plate can cause a bad squeaking/scraping sound. 

that dont sound like tranny to me. sounds like motor bottom end possibly. how is the oil pressure ? has it changed any in the last few weeks or so ? what color is the motor oil ?


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## White Gardens (Oct 29, 2008)

sweetk30;1207329 said:


> do us a favor if you will. remove the convortor bolts. slide the convortor back to the tranny. then fire up the motor. easy test to eliminate motor or tranny problem.
> 
> and a cracked but not fully broken flex plate can cause a bad squeaking/scraping sound.
> 
> that dont sound like tranny to me. sounds like motor bottom end possibly. how is the oil pressure ? has it changed any in the last few weeks or so ? what color is the motor oil ?


Your probably right about sliding back the converter and eliminating the possibilities. I might try a stethoscope first.

Oil looks good, and oil pressure has been normal for the motor and hasn't changed from what I can tell. That's why I don't think it's the motor, but it's a possibility as I've had that suspicion too.

My mechanic is off of work tomorrow, so I'll corner him and get it diagnosed. I didn't want to crack into it too far tonight as I couldn't get the inspection cover completely off. I had enough room to turn the motor over and check the bolts, but the exhaust was in the way, so I wasn't able to remove it completely.


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## White Gardens (Oct 29, 2008)

*Eureka!*

Or at least I think so.

After taking the truck out tonight to throw a load of salt, it dawned on me.

I'm almost 100% certain now that it's the harmonic balancer.

1.) If it was my flexplate, or converter, the noise shouldn't go away, the way it does. Two mechanics told me that if those were the issues, it should be constant.

2.) If it was my transmission, it should have grenaded by now or at least started acting funny.

3.) If it was the motor making such a racket, the noise again shouldn't have gone away, and only gotten worse. That and it would have grenaded by now also. It ran extremely well tonight.

4.) I remembering having a Ford Tempo (Yes I said Tempo:laughing in High School that had the harmonic balancer go out on it. It made the same noise in almost the same conditions as this issue is. I also remember it being very loud.

The noise in the video made me realize that when I shot it, the truck was still extremely cold from the 6* day we had. Tonight when driving I listened a little closer and it sounds like two metal doughnuts rattling together.

So, Kiss method on this one. I'm going to start with the balancer and go from there. I'll let you guys know if it's it or not.


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## quigleysiding (Oct 3, 2009)

I had a flexplate that was cracked all the way around the bolts. The cracks looked like a star . The truck sounded just like yours.It didn't make a sound in gear.


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## White Gardens (Oct 29, 2008)

quigleysiding;1207507 said:


> I had a flexplate that was cracked all the way around the bolts. The cracks looked like a star . The truck sounded just like yours.It didn't make a sound in gear.


Dangit. Don't rain on my parade. HA!

I'll still probably check it out, better be safe than sorry.

What year was your truck quigleysiding ?


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## quigleysiding (Oct 3, 2009)

White Gardens;1207609 said:


> Dangit. Don't rain on my parade. HA!
> 
> I'll still probably check it out, better be safe than sorry.
> 
> What year was your truck quigleysiding ?


Sorry, it just came to mind after reading this. It was an older 350 that my kid used to beat on.


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## zzamud (Dec 23, 2010)

Whitegardens let me know if u doing a trans swap im from your area i could lend a hand if ya need it


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## White Gardens (Oct 29, 2008)

quigleysiding;1207923 said:


> Sorry, it just came to mind after reading this. It was an older 350 that my kid used to beat on.





zzamud;1207932 said:


> Whitegardens let me know if u doing a trans swap im from your area i could lend a hand if ya need it


Just woke up from getting some sleep after being up all last night watching lots, so I didn't get a chance to look at it again today.

Before falling asleep my neighbor mechanic called and we talked more about it. He is a ford guy and he talked to all his GM friends and they all say the same thing. Flexplate issues. He even talked about 350's breaking them all the time.

So we're going to try and take another look at it tomorrow. Even if I got started on it today I wouldn't be able to order parts for it until Monday. Being an 8.1, there isn't a whole lot of aftermarket parts for these motors. I did talk to the tranny shop that I've been talking to and they are going to look into finding me a cheaper one rather than the $444.95 I would be spending for a GM part.

Thanks for the offer *zzamud*. Even though me and my neighbor swap services all the time, he recently had twins so his "extra" time is few and far between, so I'll definitively will keep your offer in mind. Even though it's a 2wd truck and a bit easier, it's always nice to have an extra set of hands when dealing with major swaps. Thumbs Up


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## zzamud (Dec 23, 2010)

I just bought a gm flexplate for an 6.0 for 57.99 so i hope that 449.99 was install price too!! And yes i bought it thru a dealership


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## White Gardens (Oct 29, 2008)

zzamud;1208320 said:


> I just bought a gm flexplate for an 6.0 for 57.99 so i hope that 449.99 was install price too!! And yes i bought it thru a dealership


Nope. That is correct. Cheapest I've found right now is $225.00. Like I said, parts aren't as readily available for the 8.1. Heck, even GM quoted me $250.00 for the harmonic balancer.

Fuel pump for my truck. $398.00 through NAPA, $575.00 through the dealer.

I'm even crafty when it comes to parts purchases, so the sticker shock of some of these parts are killing me.


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## zzamud (Dec 23, 2010)

Wow bro. Are u buying the parts under a business or just as a walk in customer?


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## sweetk30 (Sep 3, 2006)

ask them for the part # then go to www.gmpartsdirect.com


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## White Gardens (Oct 29, 2008)

sweetk30;1208400 said:


> ask them for the part # then go to www.gmpartsdirect.com


I've actually already looked there. Here is the price. I called the dealer to verify parts number through my VIN.


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## sweetk30 (Sep 3, 2006)

thay dont do links. post up the gm # 

i might be able to dig up some more info . i got few friends in gm dealers.


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## White Gardens (Oct 29, 2008)

sweetk30;1208645 said:


> thay dont do links. post up the gm #
> 
> i might be able to dig up some more info . i got few friends in gm dealers.


I edited the post and put a screen shot in there instead of a link.


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## White Gardens (Oct 29, 2008)

It's official, it's the flexplate.

I'm hoping to get the part ordered first thing tomorrow morning. I might go ahead and try to have it shipped overnight so I can get going on it right away.

We've got small snow showers and possibly some freezing rain tonight, plus another chance of snow on Tuesday.

I'll be taking it real easy on the truck and hopefully I can get through until I get a chance to fix it. After Tuesday, it looks like the weather will cooperate to get it done.


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## B&B (Nov 4, 2006)

The p/n you're using is the newer superseded flexplate that was increased in thickness over the original used on your truck to solve this very issue. and that's where the inflated cost increase came from. Those original flexplates (p/n 12555135) were $110.00 before being superceed to the current one.

This current p/n is also the same service flexplate used on the current 572 ci 620/720 HP and all other internally balanced big block crate engines so it's hardly an odd ball unit. They just demand top dollar for it.


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## White Gardens (Oct 29, 2008)

B&B;1210462 said:


> The p/n you're using is the newer superseded flexplate that was increased in thickness over the original used on your truck to solve this very issue. and that's where the inflated cost increase came from. Those original flexplates (p/n 12555135) were $110.00 before being superceed to the current one.
> 
> This current p/n is also the same service flexplate used on the current 572 ci 620/720 HP and all other internally balanced big block crate engines so it's hardly an odd ball unit. They just demand top dollar for it.


Thumbs Up

Thanks, that's good to know about the beefier flexplate and not having to ever worry about it again. (Hopefully)

Funny you mentioned the info about it being for the larger motors. My neighbor (Worlds Greatest Mechanic Neighbor) did some research and filled me in on that info. He was floored by the price too and looked into it for me.

He's a Peterbilt mechanic and he sees much bigger, large diesel flywheels for the same price.

It is what it is in the end. I'm just glad I'm not dropping $1200.00 on a tranny swap.


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## White Gardens (Oct 29, 2008)

Update.

Flexplate and bolts should be here today. Not sure If I'm going to have the time to get it changed out before the next storm hits tomorrow. Luckily it appears to be light snow, and possibly just a salt run.

I probably could spend an all-nighter tonight doing it, but I'd rather give myself some lee-way for Murphy's law.

Will be draining the tranny fluid, and dropping the exhuast, so I'll need to buy fluid and new exhaust gaskets, just an FYI in case someone else needs to do a repair like this. The bolts were a suggestion from my mechanic as he said it's always good to use new bolts in case the flex plate was moving around the bolts and ultimately wearing them where they hold the plate in place.


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## zzamud (Dec 23, 2010)

The new flexplate should come with new bolts and a new crank adapter( at least the one i bought did) 
Not to thread jack but i found a guy n east peoria been buildn trannys for 25 years. Quted me a complete rebuild makn the 4l80e bullitproof for 750? Ever heard of them?


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## White Gardens (Oct 29, 2008)

zzamud;1214187 said:


> The new flexplate should come with new bolts and a new crank adapter( at least the one i bought did)
> Not to thread jack but i found a guy n east peoria been buildn trannys for 25 years. Quted me a complete rebuild makn the 4l80e bullitproof for 750? Ever heard of them?


Hmmm, no I haven't. The guys I talked to were out of Kankakee, and their transmissions were 800 rebuild with a new 250 torque converter. 1200 was the cost I figured total between any other misc. parts I was going to need, such as fluid.

Was that guys price with the converter? Anyways, if you want to, PM me his info and I'll talk to him in case I need a new tranny down the road.

I'll check the flywheel when it comes in, but as far as I know it's just the flywheel and no bolts. If they are with it then I will just cancel the bolt order.


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## White Gardens (Oct 29, 2008)

Thought I'd put some closure on this thread. I always hate not knowing what ended up happening on threads sometimes.

Also I thought I'd throw some info out there in case anyone runs into trouble.

If you are pushing off changing a noisy flexplate, do it, do it now.

6 hrs from start to finish.

My greatest neighbor mechanic extraordinaire did the majority of the work, I mostly handed him stuff and did anything to do to make it easy on him. I in return have to do a landscape design and help with the install this summer and that is just fine with me. Thumbs Up

Here's the photos, nothing too major. Did find a crack in the bell housing around one bolt hole. With out going into details, it will hold for now and the way the crack is moving around one mount hole, I should be ok to get the rest of the way through the season and focus on it this summer.

Any questions let me know. All I'm going to say is that I'm glad it's done before the 18" hit this Tuesday and Wednesday. Central Illionois/Chicago guys are talking about it in their threads, I'll post a link to it in my sig.

Best neighbor, mechanic extraordinaire hard at work.

Thanks for everyone Else's help or offer to help in this thread. Thumbs Up









Flexplate with the crack. The only thing that was holding it together was the steel ring in the center that was tack welded into place.









Three blows with the hammer and it came out.









Owner of the building drives this for a living. He's another awesome guy that helps out everyone. He offered up his heated shop if I ever needed it.

I pulled it back into the shop when we were done. It's been a really long time since I've driven a piece of Ag equipment this big, so needless to say I went reallllllly slow pulling it in.


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## zzamud (Dec 23, 2010)

Glad u got it fixd i just got done putn a 4l80e n a hd. Guy rebuilt trans for 750 and makes them bullit proof. Also does 4l60's for 450 he lives n east peoria so let me know if u need a trans rebuilt and i can pass his info when the time comes u need it


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## cfpd0707 (Oct 23, 2009)

I just had a slight tick too at the begining of the season. checked it out and it ended up being a the flex plate. cracked all the way around. I dunno how the started was still starting it. pretty easy swap though. especialy since I have yoders shop at my disposal... haha


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## White Gardens (Oct 29, 2008)

cfpd0707;1221330 said:


> I just had a slight tick too at the begining of the season. checked it out and it ended up being a the flex plate. cracked all the way around. I dunno how the started was still starting it. pretty easy swap though. especialy since I have yoders shop at my disposal... haha


Decent!! Always nice and appreciated to have access to a good shop.


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## Fatality (Jul 14, 2009)

Glad things worked out Nick!!!


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## White Gardens (Oct 29, 2008)

Fatality;1221355 said:


> Glad things worked out Nick!!!


Ya, you and me both! It's going to be nuts out there for the next 4 days.


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## PerfectEarth (Feb 18, 2010)

Good to see you up and smooth before your storm hits. I know the feeling of having a good buddy or neighbor who can help you thru a jamb on short notice (and for a reduced cost!)... Have fun with your massive snowstorm! I would be lying if i said I wasn't extremely jealous.


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## sweetk30 (Sep 3, 2006)

i got 1 complant :crying:

were is the pics of the NEW plate so we could see the diffrence of the old style to new style.


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## White Gardens (Oct 29, 2008)

No noticeable difference in the look.

The new one felt heavier, but without a scale there wasn't a way to tell for sure.


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## B&B (Nov 4, 2006)

If you would have used a mic on both the old and new one you would have discovered the new one was .020 thicker. The thickness was increased solely to prevent the cracking issue. :waving:


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## EvenCutLawnCare (Aug 12, 2008)

B&B;1221669 said:


> If you would have used a mic on both the old and new one you would have discovered the new one was .020 thicker. The thickness was increased solely to prevent the cracking issue. :waving:


Your knowledge amazes me!


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## Nasty-Z (Nov 7, 2009)

Glad to see the flexplate resolved the issue .

TOM


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## White Gardens (Oct 29, 2008)

B&B;1221669 said:


> If you would have used a mic on both the old and new one you would have discovered the new one was .020 thicker. The thickness was increased solely to prevent the cracking issue. :waving:


Ya, I thought I had a mic to check it out, but it wasn't in my tool box. I'm guessing though that .020 was the bit of weight difference that I was feeling.


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