Front Differential Noise

RCTaylor · January 13

I have a 2021 GMC 2500 Hd Denali, and in mid October my local Dealer replaced seals on the Front Diff under warranty. Just before Christmas I had a need to engage the Auto 4 wheel drive and there was a serious growling noise or vibration. I took it to a Dealer in Ontario and they found the front Diff was 2 liters low. They filled it and reduced most of the noise, but I can still hear it! I plan on keeping this truck for a long time, my last 2500 was 14 years old when I got rid of it. The local dealer from talking to him believes it must be a front U joint! I have about 90K on the truck and soon out of warranty. My local dealer says that the front Diff is always turning and therefore it could not have been from the low oil! There is no sound in two wheel drive. I am concerned that it has affected the ring gear and or pinion! Any input?

Thanks

Richard Taylor

AndrewF · January 14

I could be wrong but I thought in 2hi the axle shafts disengage inside the front case and don’t turn the differential gear set. Otherwise the front driveshaft would turn all the time (granted that is disconnected in the t-case).

I would be quite upset if they did that work replacing the oil seals and didn’t bother to check/fill oil level. I’d go back and complain or call another dealer.

Another JR · January 14

The spec quantity for the front differential is 1.9 quarts from what I’ve read. If it was 2 quarts low it was empty, meaning they forgot to fill it after changing the seals. They should be replacing your front differential.

RCTaylor · January 14

I guess I will find out what they plan Thursday afternoon! Ill let you know.

Thanks

Pryme · January 14

3 hours ago, RCTaylor said:

I guess I will find out what they plan Thursday afternoon! Ill let you know.

Thanks

If they did indeed send it out with no fluid, the long term longevity has been diminished and I would be demanding a new front diff.

Incompetence is a real problem in this day and age. It’s not your problem they screwed up. Don’t let it become your problem down the road.

Chuck FB · January 14

6 hours ago, RCTaylor said:

I guess I will find out what they plan Thursday afternoon! Ill let you know.

Thanks

Do you have a spot you normally park the truck that is a surface which shows up oil leaks. Lets say for example you park in a garage with a cement floor or a cement pad in front of your garage ( if there is no snow ), it doesn't take much oil dripping off to show up on such a surface. If no oil has been spotted beyond whatever may normally dribble from the truck, odds are there was no leak and splattering of oil under the truck because there was no oil in the diff to leak out. Also the only way I could see all the oil having leaked out is if the diff cover gasket was not holding at the bottom area of the diff to cover.

As far as I know when GM went to the independent front suspension system all those years ago with the 1/2 ton initially, the transfer case definitely disconnects drive to the front drive shaft on its end and the disconnect on the right side of the front diff disconnects so that takes the right front tire turning when driving out of the picture in affecting the front diff as its no longer connected. That leaves the left front tire still being connected to the left side gear within the diff and as crazy as it sounds that left side gear is now spinning and turning the two internal diff pinion gears ( often referred to as spider gears ) and in turn the right hand side gear. The torque it requires to turn those internal diff carrier gears is typically a lot less than it would take to spin up the whole diffs ring and pinion and drive shaft going back to the transfer case. Its never made sense to me in how those carrier gears spinning constantly could be good for them but yet they seem to live ok ... as long as there is oil in the diff housing. No oil in the diff housing, it would only be the residual oil that was on the gears and the shaft the spider gears are spinning on and I can't see them being too happy after being driven some distance with zero oil in the diff housing to feed oil around to supply the gears and shafts/diff housing they run within as I suspect at some point they could seize on their shafts/diff housing and then it would cause the turning force of the left tire to turn the ring gear and pinion as its free to turn but just with more torque having to be applied. Speculation on my part but logic would say if the diff is void of oil and four wheel drive is selected and now the ring and pinion are turning and with torque applied as well to move the vehicle, damage will be taking place to the ring and pinion surfaces and the carrier side bearings as well as the pinion bearings are not being fed with oil and it wouldn't take too long to compromise all the internals of the diff and hence the howling as it was NOT a happy camper. Then oil was put into it and yes now it has lubrication but bearings/gears are now damaged and while its making less noise because it has oil now, your still hearing the damage that was caused when it was being run with no oil and I assume especially when four wheel drive is engaged ?. At that point having to replace everything in the diff, I suspect its cheaper for parts and labour ( as well as screw up idiot factor ) to have the whole diff housing swapped out with a new unit.

They could change both front cv shafts until the cows came home but that would not fix the diff and more than likely your going to hear the same noise even if they tried to sluff it off as a bad cv shaft. Not to say that there could not also be a bad cv but it doesn't take a rocket scientist ( speaking of the dealership ) to figure out that bad things happen when a diff is ran without oil !.

Edited January 14 by Chuck FB

RCTaylor · January 14

You are thinking exactly as I am! I have grown up with heavy forestry equipment and trucks, and common sense says that if after they put the oil in the Diff and the noise has almost gone away, I have damaged bearings and possibly ring gear and Pinion! I am certain that when I take the truck to the Dealer who replaced the seals and told me over the phone when the second dealer discovered no oil that it is likely a U joint, I am expecting nothing good! There are few things we can do to these new trucks beside change the oil and grease them and that is how I found the leak in October when they replaced the seals. I know they are going to say they filled the Diff, but the second dealer found no leaks! I think they will not be willing to admit that mistakes happen and the Tech failed to complete a crucial step! I'll let you now what I find out tomorrow!

Chuck FB · January 14

3 hours ago, RCTaylor said:

You are thinking exactly as I am! I have grown up with heavy forestry equipment and trucks, and common sense says that if after they put the oil in the Diff and the noise has almost gone away, I have damaged bearings and possibly ring gear and Pinion! I am certain that when I take the truck to the Dealer who replaced the seals and told me over the phone when the second dealer discovered no oil that it is likely a U joint, I am expecting nothing good! There are few things we can do to these new trucks beside change the oil and grease them and that is how I found the leak in October when they replaced the seals. I know they are going to say they filled the Diff, but the second dealer found no leaks! I think they will not be willing to admit that mistakes happen and the Tech failed to complete a crucial step! I'll let you now what I find out tomorrow!

Correct, and very possible to have damage on the carrier where the side and spider gears run, depends if there are thrust washers behind them but also the side gears could wear the bore of the case as well. While in two wheel drive there isn't the stress on them but just that they are turning and lacking oil, never mind the ring/pinion/bearings after it was run in four wheel drive for a while.

All you can see is what the dealer has to say but if that goes in the wrong direction then I presume the other dealer in Ontario created paper work to indicate the lack of visual leak and yet the diff was down 2 quarts which is the whole volume of oil it holds. It may have to elevate to GM corporate but again, see what your local dealer is willing to make whole again due to most likely their own negligence that caused this whole mess.

Edited January 15 by Chuck FB

RCTaylor · January 16

Yesterday, they took the truck for a drive returned said there was no noise! I got the Manager back into the tuck and took him for a drive. He initially said that the noise was common when in 4 wheel drive, I told him that not for my truck! He immediately said they will pull the differential and replace the bearings! Hard to believe but they stand emphatic that the Dealer in Ontario did not add fluid! I asked him then why did the noise practical disappear after!

I have spoke with a couple mechanics locally and they feel, the new bearings will probably do the job and that it is likely the ring gear and pinion will be still fine because I did not drive it any distance in all wheel. I guess I will know after they replace the bearings February 2nd.

I appreciate all the feedback and will let you know!

RCTaylor · February 4

Got the truck back today they replaced all the front differential bearings. I had the chance to look at the ring gear and pinion when they removed it and they both seemed fine with no chips or damaged teeth. I checked to bearings they removed one seemed really rough but it is hard to tell. I still feel I hear the noise but can't be sure that now that I have had the issue I am being too critical. If anyone has a similar truck do me a favour and put it in Auto and see if there is an increase in drive line noise. I really notice if i am simply traveling with no torque or coasting, and add power and i hear the increase. I want to be fair but never noticed that happening before they left the oil out.

Any help is appreciated.

Chuck FB · February 4

At what speed do you tend to notice it when you are in 4 auto and is this a dry road or slippery surface as the auto system would try to transfer torque to the front end if it was slippery.

The bearings themselves, were they paired together with the outer race and the matching bearing assembly and you were turning the bearing within the outer race. Sometimes the outer race itself that you can easily visually see the surface of may not happen to show the damage that lets say the rollers themselves may have some scaring or pitting etc but what one can't see is the inner race as the roller/cage assembly is hiding that surface. If you felt a bearing unit be noticeably rough and its clean so there is no dirt/debris, that is certainly a telling sign it was not healthy like it should have been. If I think if it in the coming days I will try my truck to see if I hear anything but to be honest in the times here and there that I have used the four wheel drive so far I can't really say I have detected any noise but you know how it is with having the cab fan running or radio and just didn't notice it. Some vehicles have certain swishing type sounds or a slight whine, so far I haven't noted that on my truck but will have to pay closer attention to it.

One thing that I would highly suggest you do as soon as your able to and sure it may sound ridiculous given what they just did but park it on level ground and let the front diff oil settle and check its level, see if its full or down a bit from the fill plug, another words lets hope they put oil in it this time !.

newdude · February 5

14 hours ago, RCTaylor said:

Got the truck back today they replaced all the front differential bearings. I had the chance to look at the ring gear and pinion when they removed it and they both seemed fine with no chips or damaged teeth. I checked to bearings they removed one seemed really rough but it is hard to tell. I still feel I hear the noise but can't be sure that now that I have had the issue I am being too critical. If anyone has a similar truck do me a favour and put it in Auto and see if there is an increase in drive line noise. I really notice if i am simply traveling with no torque or coasting, and add power and i hear the increase. I want to be fair but never noticed that happening before they left the oil out.

Any help is appreciated.

Noise in Auto is normal. The transfer case will send power as needed. At a minimum the split is 95% rear 5% front power transfer.

You can hop in a brand new one on the lot, go from 2HI to Auto and you'd hear a difference.

Edited February 5 by newdude

Chuck FB · February 6

I tried both the 4 auto and 4 high today at highway speeds and while I had the radio and cab fan off, the highway surface and studded winter tires make some noise but I could tell there was a little bit of noise coming from the system when I had it engaged and would give it a bit more throttle which also would cause the transmission to downshift, I really couldn't hear anything extra if the truck was almost in a coast mode with little throttle. No doubt there will be slight differences from one vehicle to the next and while what I hear does not alarm me as unusual, it may concern the next person. I've had various whines or sounding off type noises on vehicles over the years when engaged in four wheel drive and has done that throughout the life of the vehicle and never caused an issue. Some transfer cases have distinct noises as well and in some instances these noises can change according to tire rotations due to the slight change in tire wear diameter.

I realize this isn't of much help but I hope they caught any worn items from the misfortunate situation and they did replace the bearings as the gears looked ok, you caught it before the whole thing piled up and it certainly would have. It is possible that the gear pattern got set slightly different although I can only speculate that they tried to keep all shims the same since the same gear set was used and more so the bearing swap but still possible the gears are not quite in the same mesh pattern and could cause a little noise as a result.