02 GMC Envoy Whining Noise

[CReynoldsMIZ]

Hey guys, new to the forum but I had been around to the old (Trailvoy) forum awhile ago. So I bought this car from my grandfather in Jan of 2010 (he was original owner) and so far have had not had any problems with it at all except one. Ever since I got it, there is a noticeable whine coming from the rear of the car. Here's how it goes, when im cruising along at highway speeds it can be loud enough to be very annoying. It is not a wheel bearing, because when i let off the gas and coast the noise goes away about 2 seconds after I lift my foot off the pedal. It also will make this noise when cruising around town. It doesn't seem to do it as much at lower speeds, and seems to do it mainly around 2300-2700 rpms. Im originally thought it could be the fuel pump, but one of my buddies uncle's thought it could be coming from the rear differential. I bought the car with 81,000 miles, and it now has 120,000, and although the car runs excellent and has been maintained, I dont think any of the drivetrain fluids (Front and Rear Diff, Transfer Case, Transmission) have ever been changed. Could there be a bearing somewhere in the drivetrain that would make this whine noise only when I have my foot on the petal? Any help you guys could give would be awesome!

 

[CaptainXL]

I dont think any of the drivetrain fluids (Front and Rear Diff, Transfer Case, Transmission) have EVER been changed

Welcome! Sounds like your in the dark. Check and change all these fluids before making any jumps to other conclusions. They are supposed to be done ever 50,000 miles. Very well could be you have no fluid in the rear diff. If it's low then I would check the rear wheel axle seals for leakage.

 

[STLtrailbSS]

don't isolate to the rear sound travels i was dead set on rear diff about 2 weeks ago, spent about $300 doing early maintenance and swapping parts. Front wheel hub & new brake motive rotors...sound gone no where near the back. you can check your diff fluid with a 3/8 ratchet pull the plug and stick your pinky in you should feel fluid. also this might sound crazy whining noises have been made from the tensioner pulley up front as well. Best way is to take your time jack it up and see if you can create that noise even if in a faint way. Its hard to go off a noise and explain it over the internet I know the feeling lol

 

[Simon01]

If it whines when you're on the gas but goes away when you let off the gas, definitely sounds like a rear diff noise to me. All rear ends will have a certain amount of whine in them. My pickup went through 3 rear ends before they finally got the pattern correct. It used to whine at 45MPH, but with the last ring & pinion, it will whine around 70 because they added a shim to adjust the contact pattern.
It's not neccessarily a bearing. Has it done it all the time, since new?
Probably wouldn't hurt to pull the cover and replace the fluid. Try to see if there is any metal material in the fluid. Just make sure the fill plug comes out before you drain it.

 

[CReynoldsMIZ]

Welcome! Sounds like your in the dark. Check and change all these fluids before making any jumps to other conclusions. They are supposed to be done ever 50,000 miles. Very well could be you have no fluid in the rear diff. If it's low then I would check the rear wheel axle seals for leakage.

Yeah, i know they are supposed to be done every 50K, but i didnt own it until 80k so not for sure if anything had ever been done before me.

don't isolate to the rear sound travels i was dead set on rear diff about 2 weeks ago, spent about $300 doing early maintenance and swapping parts. Front wheel hub & new brake motive rotors...sound gone no where near the back. you can check your diff fluid with a 3/8 ratchet pull the plug and stick your pinky in you should feel fluid. also this might sound crazy whining noises have been made from the tensioner pulley up front as well. Best way is to take your time jack it up and see if you can create that noise even if in a faint way. Its hard to go off a noise and explain it over the internet I know the feeling lol

I doubt it is the tensioner. Like i said, it only happens when the car is moving certain speeds. Cant seem to replicate the sound in the driveway...I firmly believe it is in the rear because I have actually ridden in the back a few times and it is definitely louder back there than the front.

If it whines when you're on the gas but goes away when you let off the gas, definitely sounds like a rear diff noise to me. All rear ends will have a certain amount of whine in them. My pickup went through 3 rear ends before they finally got the pattern correct. It used to whine at 45MPH, but with the last ring & pinion, it will whine around 70 because they added a shim to adjust the contact pattern.
It's not neccessarily a bearing. Has it done it all the time, since new?
Probably wouldn't hurt to pull the cover and replace the fluid. Try to see if there is any metal material in the fluid. Just make sure the fill plug comes out before you drain it.

Okay, I think you are on the right tract. What exactly is the pattern, or contact pattern? Im assuming it is how the gears line up inside of the diff? Im not sure if it has done it all the time, but it has definitely done it since I have got the car. Im sure it didnt do it since new, because my grandfather is the type of person who would have it looked at by the dealer right away if it was making a weird noise...me, not so much....


Can someone walk me through changing the fluids? Is it as easy as it seems, just remove the bolts that hold the cover on and let it drain? I have seen a video from one of the members...May03SLT or something like that on youtube, doesnt seem to difficult...get it *diff*icult...lol wordplay. I have never seen a leak from the rear diff, so will i need to replace the gasket as well? What about using silicone? Does that need to be used? I know your supposed to wipe it out and any metal shavings from the magnet or something, then replace cover and fill to bottom of threads on top fill. Also, I know it is a GM fluid or something that is only supposed to be used in there, can someone tell me the name of it again? Am I supposed to use it in the front diff as well? Okay, ill take a break thats alot of questions. Any other input on culprits would be great as well! Thanks, love this forum. I have some other repairs/projects I need to tackle (as soon as I graduate college *2 months* so the car has been kind of neglected since I started, but cant wait to get greasy again!

 

[CaptainXL]

Yeah, i know they are supposed to be done every 50K, but i didnt own it until 80k so not for sure if anything had ever been done before me.

Can someone walk me through changing the fluids? Is it as easy as it seems, just remove the bolts that hold the cover on and let it drain? I have seen a video from one of the members...May03SLT or something like that on youtube.

I would suggest a Haynes manual. If May03Lt has a video all the better but you should have a manual by your side if you feel confident doing this. If you never have done it before I would recommend a dealer or other shop change all 4 fluids for you. This is tranny, front and rear diff and trans case. It should have been done when you got the vehicle or at 100k at the very latest. Remember changing those fluids every 50k isn't so much for changing the fluid as it is for inspecting the levels and condition. Fluids are very seldom changed by previous owners at 50k.

 

[STLtrailbSS]

Step 1:
Get under your truck with a 3/8 Ratchet Use a good one if you got one because you need to first check if you can brake loose your Fill plug because if you can not break that and you drain the diff your in a whole other world of issues.

If you can break that loose you are clear to go. Remove all bolts (Be careful with the diff bolts) drain your diff remove old gasket and place new you can use RTV sealant also with your gasket although it is not completely necessary.

Next you want to use the right gear oil 75w-90atlest thats the weight recomended for the 14bolt rear end. Mobil 1 will work. For the next part I need a i6 Owner to step in. On The SS model our rear end needs a friction modifier additive that is added to the diff oil after it is replaced. So dont quote me on that till a 6 owner chimes in.

Clean your pan place your gasket bolt and fill and your done pretty straight forward. Not very difficult. The ss model is frustrating just for the fact how low it sits. Lifted guys have the life with this task.

red areas need i6 owner review lol


should look like this lol

 

[CaptainXL]

Eaton G80 govlock lockers don't need friction modifier added but can be used. It's mostly used in the posi Trac limited slip diffs.

The gasket for the rear is reusable. Mobile 1 LS synthetic 75w-90 already has friction modifier in it so can be used for all trailblazers.

 

[STLtrailbSS]

see tbss owners has had this issue and I found this straight from mobil. Its for a vette but they are saying its not meeting GM spec. Don't know if this comes close to applying to the TBSS but always bugged me. Hijack post sorry.
Gear Lube to Use in Newer Corvettes

 

[Wooluf1952]

To the OP;
Your 2002 should have a drain plug. That will help to keep down the mess. The gasket is reusable, but you may want to get a new one just in case. You can always return it if you don't need it.

 

[CReynoldsMIZ]

Okay. So Mobil 1 LS 75W-90. Is that the consensus? I forgot to mention, yes this is the 02 Envoy SLT, 4WD SWB. Im sure you guys knew that but just wanted to make sure. I thought that I was under the impression that only GM fluid can be used in this? Maybe im thinking of transfer case. Do you know how much fluid I will need? Im not going to take this to the dealer, I dont really trust others to work on my stuff, dont like being taken for a ride on their labor costs, plus i can turn a wrench just fine.

 

[CaptainXL]

Okay. So Mobil 1 LS 75W-90. Is that the consensus? Ie.

You can use whatever brand you want. The capacities are in the manual which I would get if you really can turn a wrench.

But just in case your too cheap to get one its found using a simple search or by taking my word for it. Fill it with exactly two quarts.

 

[meerschm]

Okay. So Mobil 1 LS 75W-90. Is that the consensus? I forgot to mention, yes this is the 02 Envoy SLT, 4WD SWB. Im sure you guys knew that but just wanted to make sure. I thought that I was under the impression that only GM fluid can be used in this? Maybe im thinking of transfer case. Do you know how much fluid I will need? Im not going to take this to the dealer, I dont really trust others to work on my stuff, dont like being taken for a ride on their labor costs, plus i can turn a wrench just fine.

Transfer case takes special fluid. dealer parts counter should have it. you can call them, they also should be able to give you a price for the GM specific differential fluid, which will make you glad for whatever you pay for the Mobil 1

 

[CaptainXL]

see tbss owners has had this issue and I found this straight from mobil. Its for a vette but they are saying its not meeting GM spec. Don't know if this comes close to applying to the TBSS but always bugged me. Hijack post sorry.
Gear Lube to Use in Newer Corvettes

No. I believe you can use the ls mobile 1 but you need to add additional modifier to make it compliant with the GM spec for performance rear ends. Mobil 1's website even mentions this.

 

[STLtrailbSS]

I'm on my phone right now but AMSoils. Website has a great database of fluid capacitys. To the right of the page. for future reference

 

[CaptainXL]

Transfer case takes special fluid. dealer parts counter should have it. you can call them, they also should be able to give you a price for the GM specific differential fluid, which will make you glad for whatever you pay for the Mobil 1

The fluid for the transfer case is called Auto-Trac 2. About $11 a quart. You can also use Royal Purple Synchromax. Fill is 2 quarts as well.