Noise after differential fluid change?

[dross99_si]

Hey guys we have a 2007 LT 4WD and after I changed the front and rear differential fluid the Tahoe has a whine only when cold. After it's driven for a few miles it goes away. Noise is speed dependent and almost sounds like when you drive a manual trans in reverse. Like that high pitched siren whine.
I put Lucas synthetic 75-90 in both differentials, which I don't believe has limited slip additive - not even sure if we need limited slip additive in the rear diff on these vehicles..?
I also found out after the fact that the front diff is supposed to have 80-90 GL5.
What do you guys suggest? Would the 75-90 synthetic screw up the front diff? Does the rear diff require limited slip additive?
Please advise.

 

[02Lightning]

If it were me, I would change out the front diff to 80-90 GL5 so I have piece of mind. If it needed limited slip additive, it would be grabby around corners. Did you double check to make sure the fluid is full?

 

[dross99_si]

If it were me, I would change out the front diff to 80-90 GL5 so I have piece of mind. If it needed limited slip additive, it would be grabby around corners. Did you double check to make sure the fluid is full?

They’re definitely full. I’ll get some 80-90 GL5 and see if that fixes it. Hopefully the 75-90 synthetic didn’t do any long term damage

 

[swathdiver]

They’re definitely full. I’ll get some 80-90 GL5 and see if that fixes it. Hopefully the 75-90 synthetic didn’t do any long term damage

Shouldn't be a problem having the 75W90 up front, lots of guys do it without issue. Could the noise be the transfer case? Now that you've put fresh fluids in your differentials, it may have quieted them down so now you hear the TC.

If you want to compare your noises to mine let me know, haven't run mine today.

 

[dross99_si]

Shouldn't be a problem having the 75W90 up front, lots of guys do it without issue. Could the noise be the transfer case? Now that you've put fresh fluids in your differentials, it may have quieted them down so now you hear the TC.

If you want to compare your noises to mine let me know, haven't run mine today.

There’s definitely something going on. This noise is new and started after changing the diff fluid. One thing after another man..

 

[swathdiver]

There’s definitely something going on. This noise is new and started after changing the diff fluid. One thing after another man..

Ok, well let me know if you want to put the whole thing up in the air on jackstands and run it slow to isolate the noise.

 

[dross99_si]

Ok, well let me know if you want to put the whole thing up in the air on jackstands and run it slow to isolate the noise.

Thank you

 

[Derick]

When I had my toyota sequoia, it REALLY didnt like synthetic fluid. I put lucas in there, and I didnt have any problems that I know of. That said, when I did the burb, I used valvoline synth with the limited slip additive.

 

[dross99_si]

When I had my toyota sequoia, it REALLY didnt like synthetic fluid. I put lucas in there, and I didnt have any problems that I know of. That said, when I did the burb, I used valvoline synth with the limited slip additive.

Thanks

 

[swathdiver]

There’s definitely something going on. This noise is new and started after changing the diff fluid. One thing after another man..

How did the magnets look? No flakes, just dust?

 

[dross99_si]

How did the magnets look? No flakes, just dust?

Just dust. Nothing crazy.
So strange that the noise occurs only when cold and virtually disappears after a few miles of driving.
Like I said earlier it sounds similar to a manual trans driven in reverse.

 

[swathdiver]

Just dust. Nothing crazy.
So strange that the noise occurs only when cold and virtually disappears after a few miles of driving.
Like I said earlier it sounds similar to a manual trans driven in reverse.

And you're certain it's not coming from the transfer case? Did you say it's coming from the front or rear diff?

 

[dross99_si]

And you're certain it's not coming from the transfer case? Did you say it's coming from the front or rear diff?

I seriously don't feel that its the transfer case. Last time I changed the fluid on that was 2016 (20K miles ago).
Can't tell for 100% sure if it's coming from front or rear. I want to say it's the front though.

 

[swathdiver]

I seriously don't feel that its the transfer case. Last time I changed the fluid on that was 2016 (20K miles ago).
Can't tell for 100% sure if it's coming from front or rear. I want to say it's the front though.

My front axle is/was getting noisy and I started using Lucas Oil in it too. Didn't pay it too much mind. You're welcome to stop by and compare it to mine. Should be home tomorrow. Someone can stand next to the truck as you drive by when cold to see which axle the noise is coming from, or put it up on jack stands and pit it in drive while someone crawls under and has a listen.

 

[dross99_si]

My front axle is/was getting noisy and I started using Lucas Oil in it too. Didn't pay it too much mind. You're welcome to stop by and compare it to mine. Should be home tomorrow. Someone can stand next to the truck as you drive by when cold to see which axle the noise is coming from, or put it up on jack stands and pit it in drive while someone crawls under and has a listen.

Doing that on jack stands makes me nervous hahaha

 

[swathdiver]

Doing that on jack stands makes me nervous hahaha

That's why I mentioned doing it over here with two people. I've got a couple of 3-ton floor jacks and plenty of 3-ton stands, wheel chocks, etc. Even different fluid.

Be forewarned, my youngest daughter and I have a cold still.