Whining sound just started (after towing a car)

[Slimpee]

This past weekend, I used my 2021 Yukon with the 5.3L motor and Max Trailering package to tow my convertible to the Sandhills Open Road Challenge. I had three adults, two kids, two small dogs, and luggage in the Yukon and the car on a Uhaul car trailer. I'm strongly leaning towards a diesel model if I buy another Yukon but overall, and she sagged quite a bit in the rear, but I was impressed with the Yukon's towing performance. She seemed perfectly happy and didn't see any coolant or transmission heat issues.

However, I got back Sunday night and yesterday, I noticed a whining sound when I apply throttle. It seems to occur in both Drive and Reverse, although I haven't tried much in reverse. It increases in pitch a bit as RPMs rise and decreases as they fall. I don't notice it as much once i'm up to in-town speed but I also haven't tested it a lot yet. I can't tell yet if it's coming from the motor, transmission, or rear end.

I'm sorry for being vague and i'll update if i get more information, but with what i've provided, anyone have any ideas?

 

[West 1]

I would get under it and look for oil leaks. At the front axle check the pinion and where each axle stub comes out of the differential.
At the rear check at each wheel, a leaking axle seal will put oil on your rim. Also check the rear pinion seal where the driveline attaches.
A leak will mean the unit has low oil and possible damage to your bearings inside.

 

[jfoj]

Transmission pump gears can get noisy because of the helical cut wearing the bearings and boss. Search YouTube and you may find a video of the 10 speed pump gear whine noise. Straight cut Ford pump gears are the best replacement option and they are a direct drop in replacement. A good transmission shop will know about them and could also confirm if the noise is from the transmission pump.

 

[West 1]

Another consideration, it may have nothing to do with drivetrain and simply be a Belt idler or power steering whine, maybe a failing alternator?

 

[Slimpee]

Thank you for all of the replies! I'll get under the car tonight and look for leaks. I think it could be the transmission pump gear but will investigate further. Luckily, if it's a drivetrain issue, it'll be covered under the CPO warranty.

F this thing. I'm dumping it before I lose the CPO powertrain warranty. So far, the transmission switch buttons broke, stranding me outside of my office (couldn't actuate reverse and a vehicle was parked in front of me so i couldn't drive straight out) and then, just outside dealership, the Drive button broke stranding me at a gas station. Luckily, I was across the street from the dealer so i was able to get it there.

A fanbelt needed to be replaced (not too crazy)

Now, the drivers side AC isn't blowing cold (i posted about it in a thread on the Interior forum) and now I may have this transmission/drivetrain issue.

I've driven Mercedes for 12 years and they've all been reliable. I'm just glad I was smart and insisted on a CPO unit.

I like the Yukon and want a diesel version so i'll have to start researching the 2023 and newer units.

 

[swathdiver]

This past weekend, I used my 2021 Yukon with the 5.3L motor and Max Trailering package to tow my convertible to the Sandhills Open Road Challenge. I had three adults, two kids, two small dogs, and luggage in the Yukon and the car on a Uhaul car trailer. I'm strongly leaning towards a diesel model if I buy another Yukon but overall, and she sagged quite a bit in the rear, but I was impressed with the Yukon's towing performance. She seemed perfectly happy and didn't see any coolant or transmission heat issues.

However, I got back Sunday night and yesterday, I noticed a whining sound when I apply throttle. It seems to occur in both Drive and Reverse, although I haven't tried much in reverse. It increases in pitch a bit as RPMs rise and decreases as they fall. I don't notice it as much once i'm up to in-town speed but I also haven't tested it a lot yet. I can't tell yet if it's coming from the motor, transmission, or rear end.

I'm sorry for being vague and i'll update if i get more information, but with what i've provided, anyone have any ideas?

Don't know how much your passengers weigh but that run seems like she was overloaded, over the GCWR at the least.

 

[viven44]

Check the wheel bearings as well, especially the rear ones.

Decent tongue weight + payload in the back can definitely tax a 1/2 ton semi-floating setup.

 

[Slimpee]

Don't know how much your passengers weigh but that run seems like she was overloaded, over the GCWR at the least.

6000 for Yukon, 2200 for trailer, 3800 for car, 605 passengers and dogs, 100 luggage, 215 lbs fuel (both vehicles, full tanks)=12,920. I'm sure there are odds and ends I left out but I think i was safely under.

 

[swathdiver]

6000 for Yukon, 2200 for trailer, 3800 for car, 605 passengers and dogs, 100 luggage, 215 lbs fuel (both vehicles, full tanks)=12,920. I'm sure there are odds and ends I left out but I think i was safely under.

Seems that way. I pass by the local CAT Scales for a quick weigh when towing, have an account and app on my phone so I don't have to go in and get a weigh ticket.

 

[Slimpee]

Another consideration, it may have nothing to do with drivetrain and simply be a Belt idler or power steering whine, maybe a failing alternator?

Update: It sounds like the whine is coming from the engine bay. I couldn't pinpoint exactly where but as someone else revved the engine a bit, the whine definitely sounded like the motor. So, i suspect one of the pulleys or ancillary parts. I'll try to upload a video later.

I am also having an issue with the AC where the drivers side is warmer than passenger side, which is ice cold. I don't think the two issues are related because the air is so cold on the passenger side, but perhaps someone smarter than I will correct me.

 

[Joseph Garcia]

This past weekend, I used my 2021 Yukon with the 5.3L motor and Max Trailering package to tow my convertible to the Sandhills Open Road Challenge. I had three adults, two kids, two small dogs, and luggage in the Yukon and the car on a Uhaul car trailer. I'm strongly leaning towards a diesel model if I buy another Yukon but overall, and she sagged quite a bit in the rear, but I was impressed with the Yukon's towing performance. She seemed perfectly happy and didn't see any coolant or transmission heat issues.

However, I got back Sunday night and yesterday, I noticed a whining sound when I apply throttle. It seems to occur in both Drive and Reverse, although I haven't tried much in reverse. It increases in pitch a bit as RPMs rise and decreases as they fall. I don't notice it as much once i'm up to in-town speed but I also haven't tested it a lot yet. I can't tell yet if it's coming from the motor, transmission, or rear end.

I'm sorry for being vague and i'll update if i get more information, but with what i've provided, anyone have any ideas?

I recommend that you take the truck to a trusted local repair shop, and get the truck on a lift with the wheels off the ground and with someone inside the truck. Put the truck in gear and press the gas pedal a bit, and see if the noise also occurs in the unloaded situation (wheels off the ground). If the noise still occurs, then the Mechanic underneath the truck can go around, with a stethoscope if necessary, and locate the source of the noise.

 

[Fless]

Remove the accessory belt and the A/C belt and run it for a minute to see if the whine goes away, if it does, you'll know that it's one of the things that's driven by the belts.

 

[viven44]

I am also having an issue with the AC where the drivers side is warmer than passenger side, which is ice cold. I don't think the two issues are related because the air is so cold on the passenger side, but perhaps someone smarter than I will correct me.

That's typical of when the refrigerant is getting low (side closer to the evaporator is colder).

 

[Slimpee]

Remove the accessory belt and the A/C belt and run it for a minute to see if the whine goes away, if it does, you'll know that it's one of the things that's driven by the belts.

Good call. I have no idea how to do that but I’m sure YouTube can tell me!

 

[Slimpee]

That's typical of when the refrigerant is getting low (side closer to the evaporator is colder).

I’ve also seen people posting about a blending door not working properly.

I’ll need to find out how to add refrigerant and then get someone to find the leak.

 

[swathdiver]

I’ve also seen people posting about a blending door not working properly.

I’ll need to find out how to add refrigerant and then get someone to find the leak.

The most accurate way to add refrigerant is through a manifold. We first remove all the refrigerant and then pull vacuum for about 30-45 minutes to see if there's a leak. Then we literally weigh the charge on a scale and introduce it through the manifold.

You can buy a sniffer, manifold and vacuum pump at Harbor Freight and do this yourself. I did this when the dealer could not find my leak. I persisted and found and fixed it myself!

 

[jerry455]

These generation trucks use electric steering, no pump, and do not have a tensioner. There is an idler pulley but to remove the belt, it has to be cut and then there is a tool for installing a new one. Kind of like the old days of 1.8 and 2.0 GM timing belts using a tool to "ease" the new belt on without moving water pump tensioner.

 

[viven44]

I’ve also seen people posting about a blending door not working properly.

I’ll need to find out how to add refrigerant and then get someone to find the leak.

Yeah I suppose a bad blend door can do that as well if you have dual zone climate.

I’d definitely hook up a manifold gauge set and see what the high side and low side pressures are first.

When you are done, don’t forget to recirculate the contents from the high side hose/manifold back into the system via the low side. It is a specific process sequence to do that. If that isn’t done, a non-negligible amount of refrigerant is wasted when the gauge set is unplugged.

 

[Slimpee]

Update: I took it to the dealer and they said the whining was the idler pulley and will be replaced under CPO powertrain warranty.

They said the AC issue is a leaky rear evaporator and quoted around $1500-$1800 to replace. I called my indy mechanic and he quoted something similar. I think i'm just going to have the dealer do it unless any of you have any bright ideas.

Thank you all for the input!

 

[viven44]

They said the AC issue is a leaky rear evaporator and quoted around $1500-$1800 to replace. I called my indy mechanic and he quoted something similar. I think i'm just going to have the dealer do it unless any of you have any bright ideas.

Yes, let the dealer do it, they will warranty the job