2002 Tahoe front end whine

[zmusclow]

If I'm reading this correct it only happens in 2wd at 45-55 mph and goes away in 4wd completely? Have you ran it without the front drive shaft connected to see if it goes away in 2wd if not I would look at the rear end.

45-55 mph is pretty specific and mainly happens when something is just a tad off, or worn depending on how loud it is. When loading pitch change is probably the drive/coast change in the gears, normally drive wears worse than coast, so is it louder under or without gas?

I have been doing more diagnosing today. The noise will also disappear at any speed in 2wd if I shift the transmission to neutral. Starting to suspect rear gear setup or transmission. The noise stays consistent to the speed of the truck and does not change with transmission shifts

 

[Erickk120]

The weird part is just going away in 4wd, it should be constant, unless the extra noise is masking it, I dont think you told us how loud it was, so its a posibility. I can see how going into neutral would remove the pressure from the drive shaft into the rear gears, and therefore not transmitting enough torque to the rear to apply a load and make the gears whine. With it in gear do you note any difference while accelerating through that range vs just getting to 55 and coasting with no gas? Sometimes you can lose pinion preload but you can hear the pinion bearings coming to a stop, I did this while pulling a stump. Not saying its your rear end, but it really sounds suspect.

 

[SnowDrifter]

These rigs still spin the spider gears in the front diff while in 2wd. Don't know if that's your issue, but something to keep in mind when looking at things.

 

[zmusclow]

The weird part is just going away in 4wd, it should be constant, unless the extra noise is masking it, I dont think you told us how loud it was, so its a posibility. I can see how going into neutral would remove the pressure from the drive shaft into the rear gears, and therefore not transmitting enough torque to the rear to apply a load and make the gears whine. With it in gear do you note any difference while accelerating through that range vs just getting to 55 and coasting with no gas? Sometimes you can lose pinion preload but you can hear the pinion bearings coming to a stop, I did this while pulling a stump. Not saying its your rear end, but it really sounds suspect.

The sound is fairly loud, when under a jar acceleration the noise is not there. Thule coasting the noise quiets down. But under normal acceleration and while braking, I hear the whine.

 

[zmusclow]

These rigs still spin the spider gears in the front diff while in 2wd. Don't know if that's your issue, but something to keep in mind when looking at things.

I thought of that, but I think if it was in the front spider gears the noise would be present all of the time since there is no load in 2wd. Also would remain with trans in neutral.

 

[Erickk120]

Dont take this as face value, without pin pointing the origin its hard to tell, but to me it sounds like ring and pinion. Based on what you said.

"when under a jar acceleration the noise is not there"
I imagine you meant"HARD" which makes sense for it to go away, as the ring and pinion load against each other and the mesh patch increases, its probably still there but gets masked by other noise.

"while coasting the noise quiets down"
Makes sense as the coast doesn't get loaded nowhere near the drive side, and its under load only while in reverse.

"But under normal acceleration and while braking, I hear the whine."
Matches what a worn ring and pinion would make as far as as I know. Whine can only be gears not meshing properly/worn out or lost preload. Bad preload will cause a whine coming down to a stop in coast, all the way to like 15 mph as the gear patter is out of specs. Did you check what the fluid looks like? Also check for slack at the pinion, make sure it has 0 in and out play, and no leaks at the seal. I'm talking about the rear diff, as its the only thing under load while driving, apart from the trans, but I highly doubt its the trans. The Tcase wouldnt produce a "whine" and instead it would produce whirring from bad bearings, as there are no gears meshing against each other and its chain driven, I lied the 246 does have an planet and ring gear but you would hear it all the time if it was the case. I think its a 4 pinion planet, if I remember right, thats just me rambling but keep us updated.

 

[SnowDrifter]

I thought of that, but I think if it was in the front spider gears the noise would be present all of the time since there is no load in 2wd. Also would remain with trans in neutral.

Except that in 2wd, it will spin the spider gears. And once 4wd is engaged, the spider gears then rotate with the ring gear and from a rotational perspective - remain stationary.

The differential disconnect works by decoupling both the passenger side axle shaft, and the front drive shaft. The driver's side axle shaft, however, remains connected to the internal gears. So that means it's spinning both the side gears, and the spider gears, round and round.

Jack the front end up, unscrew the breather/inspection plug, and give the LF wheel a spin to see what I'm talking about.

 

[zmusclow]

Dont take this as face value, without pin pointing the origin its hard to tell, but to me it sounds like ring and pinion. Based on what you said.

"when under a jar acceleration the noise is not there"
I imagine you meant"HARD" which makes sense for it to go away, as the ring and pinion load against each other and the mesh patch increases, its probably still there but gets masked by other noise.

"while coasting the noise quiets down"
Makes sense as the coast doesn't get loaded nowhere near the drive side, and its under load only while in reverse.

"But under normal acceleration and while braking, I hear the whine."
Matches what a worn ring and pinion would make as far as as I know. Whine can only be gears not meshing properly/worn out or lost preload. Bad preload will cause a whine coming down to a stop in coast, all the way to like 15 mph as the gear patter is out of specs. Did you check what the fluid looks like? Also check for slack at the pinion, make sure it has 0 in and out play, and no leaks at the seal. I'm talking about the rear diff, as its the only thing under load while driving, apart from the trans, but I highly doubt its the trans. The Tcase wouldnt produce a "whine" and instead it would produce whirring from bad bearings, as there are no gears meshing against each other and its chain driven, I lied the 246 does have an planet and ring gear but you would hear it all the time if it was the case. I think its a 4 pinion planet, if I remember right, thats just me rambling but keep us updated.

I did put a new ring and pinion in it about 8 months ago. It’s was my first time doing anything like that. I’m going to pull it apart and check the lash and pattern. Hopefully it’s not too far gone. As for the fluid. I changed it today to see what it looks like. There was a small amount of metal on the magnetic plug and the oil was dark with some very tiny metal flakes but not a lot.

 

[mhaywoodcz]

Hey Guys, not trying to thread hijack but I have a 2002 Denali, similar whine from the front end. Suspect the front diff, it had wonderful glitterness in the fluid when I changed it (new to me). If I read this correctly, can I find a 4x4 with the same gear ratio front diff and add my AWD portion (can't remember the part that keeps front end engaged) and it work correctly?