Diagnosing noises 2003 Tahoe.

[James417]

Hey everyone. I am finally driving my 2003 Chevy Tahoe around and just got the new Gibson cat back installed and its running pretty good. Aside from a bad 02 sensor and some misfires I'm thinking are related to that it seems fine. But there are a few noises I am concerned about. I just noticed sense I got the much quieter cat back compared to the straight pipe there's a moan or howl kind of sound that starts at around 40 mph and just increases in volume and pitch as I accelerate. Weird thing is it completely stops if I let stop accelerating. But as soon as I start to accelerate again the noise starts too. The noise also gets quieter under heavier acceleration and only starts at around 40mph and up. If i drop into a low gear and engine brake it doesnt make any noise. It sounds like its coming from right under me or behind but its really hard to tell. Its not extremely loud but its loud enough to cause concern but it literally only happens while accelerating at 40mph or higher. Another thing I am hearing is a clunk/clank from my drive shaft between 2nd and 3rd gear shifts no matter how hard or light I am accelerating. 1st to second is a little rough but it feels like any other Chevy with a 4l60e I have riden in. And between 3rd and 4th its butter smooth. But between 2nd and 3rd it sounds like someone's hitting my driveshaft with a hammer. Maybe yoke bearing play? How much play is enough to need replacing? I notice it does make some noise also during different decelerations and accelerations like little clanks and clunks once in a while. Otherwise everything does seem fine. I should change the transmission fluid and front differential fluid sense its been sitting for a few years without running and I don't know how well maintenanced it was as a service truck. Speaking of it being a service truck thats the reason why I am suspicious of problems and noises because I have no clue how well taken care off or beat on it was. But it does have plenty of power and doesn't seem to lack at all. Thanks in advance.

 

[#1taho]

Hey everyone. I am finally driving my 2003 Chevy Tahoe around and just got the new Gibson cat back installed and its running pretty good. Aside from a bad 02 sensor and some misfires I'm thinking are related to that it seems fine. But there are a few noises I am concerned about. I just noticed sense I got the much quieter cat back compared to the straight pipe there's a moan or howl kind of sound that starts at around 40 mph and just increases in volume and pitch as I accelerate. Weird thing is it completely stops if I let stop accelerating. But as soon as I start to accelerate again the noise starts too. The noise also gets quieter under heavier acceleration and only starts at around 40mph and up. If i drop into a low gear and engine brake it doesnt make any noise. It sounds like its coming from right under me or behind but its really hard to tell. Its not extremely loud but its loud enough to cause concern but it literally only happens while accelerating at 40mph or higher. Another thing I am hearing is a clunk/clank from my drive shaft between 2nd and 3rd gear shifts no matter how hard or light I am accelerating. 1st to second is a little rough but it feels like any other Chevy with a 4l60e I have riden in. And between 3rd and 4th its butter smooth. But between 2nd and 3rd it sounds like someone's hitting my driveshaft with a hammer. Maybe yoke bearing play? How much play is enough to need replacing? I notice it does make some noise also during different decelerations and accelerations like little clanks and clunks once in a while. Otherwise everything does seem fine. I should change the transmission fluid and front differential fluid sense its been sitting for a few years without running and I don't know how well maintenanced it was as a service truck. Speaking of it being a service truck thats the reason why I am suspicious of problems and noises because I have no clue how well taken care off or beat on it was. But it does have plenty of power and doesn't seem to lack at all. Thanks in advance.

I had a similar problem and mine was the carrier bearings. I changed then and all problems are gone. you have some differences but sound to me thats what it is. I have heard some guys complain about transfer case slop too. do some checking.

My carrier bearings had no play just very noisy, they were very pitted.

 

[VikingTrad3r]

I had a similar problem and mine was the carrier bearings. I changed then and all problems are gone. you have some differences but sound to me thats what it is. I have heard some guys complain about transfer case slop too. do some checking.

My carrier bearings had no play just very noisy, they were very pitted.

hi, i just fixed mine and there is a forum post here by me as i went through it. Cheers. Easy to do. need time, space, double up the jack stands.

 

[James417]

Thanks for the response I'll definitely check out that post. I climbed used the Tahoe today and wiggled the driveshaft. It does turn a little by hand and makes a notable clunk back and forth. But by the differential there's no up and down or side to side play but at the transfer case there is play side to side and or up and down. Not a lot but enough to created a quiet knock while I wiggled it.

 

[VikingTrad3r]

Thanks for the response I'll definitely check out that post. I climbed used the Tahoe today and wiggled the driveshaft. It does turn a little by hand and makes a notable clunk back and forth. But by the differential there's no up and down or side to side play but at the transfer case there is play side to side and or up and down. Not a lot but enough to created a quiet knock while I wiggled it.

90% sure your carrier bearing lick tab is broken and has allowed one of the carrier bearings to back out (ie, create slop, reduced preload) which translates to increased backlash, which u feel as slop. same as me.

 

[southboundchicken]

Have u considered the u joint ? How many miles are on it ? Mine went bad about 150,000 miles. They were pretty cheap to replace

 

[#1taho]

hi, i just fixed mine and there is a forum post here by me as i went through it. Cheers. Easy to do. need time, space, double up the jack stands.

What was it???

 

[VikingTrad3r]

What was it???

carriers. http://www.tahoeyukonforum.com/thre...ont-diff-carrier-bearing-install.75857/page-2

 

[James417]

There's 138,250 miles on it right now. I'm about to install a downstream o2 sensors I ended up ruining by running the truck with the cat back exhaust for a few months. Lol. Well I'll be getting that in doing an inspection so its road legal again temp inspection ran out. But is it safe to drive with the bad bearings? In have ridden in other trucks with bad bearings that where much worse sounding. But the snow will be falling soon here and I would like to limp the bearings along. I'll probably have the money and time to do it in December but it maybe snowing or something by then. Smh. Northeast is a pain. My biggest worry other than that is making sure I keep the rust and rot to a minimum. Not to long ago I sanded and bondo and repainted the bottoms of my doors from rusting and flaking caused by sitting for so long. But now the paint is peeling and surface rust is back and flaking off my Hondo and paint. So I will be re doing that this coming spring with the rotted rocker panel. Lol

 

[VikingTrad3r]

first things first man, go to your local auto supply store/hardware store and get some SAE80W–90 gear oil buy 2 quarts of it or if you're in Canada like me 2 liters. do yourself a really big favor and buy one of those pumps for the top that just screws onto the top of the bottle like in the picture here the pump was seven dollars.
Here where i live, 80w90 gear oil costs 7$ a bottle and it takes 2 bottles to fill the diff.

so for a total of $21 Canadian probably less in the states, get under the front of the car you don't even need to lift it if you don't want to you can just pull the front up onto the curb and first crack open the fill plug which is the top plug and it is a different size than the drain plug on the front diff, you always want to make sure you can open the drain plug, like it's not seized, so that after you drain the oil from the bottom plug you can definitely refill it!

grab the screw on pump that you bought it'll come with hoses and start pumping fluid back into the top fill plug and stop as soon as it starts to drip out the fill plug. you are then full.

if you keep clean fluid in there, you can definitely drive with the bearings are bad just know that the vibration caused by the bad bearings will slowly impact the really expensive gearing that is inside the differential. my guess is if the noise is not really really really bad right now, that your gears are just fine like mine were. The other thing I would do is add some Lucas product to your differential fluid and it will help you limp along for sure. The Lucas oil stabilizer does not fix the problem. But it will definitely help you limp along without a doubt my guess is that when you drain your diff fluid, it's going to be like a silver color, just like mine, and your drain plug will have a whole bunch of metal on it. if the metal art chunks versus small filings then you have a big problem, only if it's chunks of metal. The small filings are coming from the bearings.

I did a $14 fluid change, One week before I pulled my differential out and it cleaned up the inside really good for when I opened it.

anyway long story short drain it take pictures of it see how bad it is if it's really bad with chunky bits of metal then you should do something about it right away if there are no chunks just small filings then just add fresh fluid put in 25% Lucas heavy duty oil stabilizer and just run with it.

if it is your daily driver, I probably change the oil again in three months you're going to find it full of metal shavings again as your bearings continue to break down the Lucas heavy oil student stabilizer should at least slow that a little bit.