Humming noise from tires after transmission replacement

[penz08]

Good day,

I recently had my 2018 Mazda3 GS automatic transmission replaced, the idiots at the dealership replaced the original one due to a 3rd and 5th gear malfunction (there was an actual bulletin made by Mazda for this) and they overfilled the new transmission with the wrong fluid and added way too much, resulting in a blew transmission once again after only 25 000 km.

Now, they did the job all over again, put a brand new transmission in, the correct oil with the correct amount ( I assume). The transmission shift like it supposed to, like a brand new one, smooth and quick.

I took my car to a well known alignment shop after that since it was due anyways for an alignment, so after the transmission replacement, I took it for a four wheel alignment.

My problem at this moment, I hear an intermittent humming noise that become more evident around 100 km/h (60 mph) or more, around 80 km/h I hear basically nothing but thread noise on rough pavement surfaces. I does not sound like a wheel bearing, its not worse when cornering, but only at highway speeds on a strait line. The car drives strait.

I currently have four Michelin Defenders T+H since 2019 on the car. I did put them around 30K km brand new, I have now 157k km on the car. These tires seems to be louder and louder with aging and heat cycles over time.

Now, my question, is it possible its only a tire issue? uneven wear? I have no idea if they rotated the tires the right way when they installed it this spring, I had winter tires on, they are Bridgestones Blizzaks WS90 and are actually very quiet and ride well. I could almost say they ride quieter than my Michelins currently on rough pavement.

I assume the transmission was installed properly, correct oil and quantity this time around, shifts like a dream, smooth. The alignment was done. It leaves me with a tire issue.

Anyone experienced a humming noise over 60 mph (100 km/h) ?

Feel free to ask for more details if I missed something.

Thank you!

 

[Rand]

install your other set of tires for a day to see if its the tires?

I could believe its the tires getting louder.

 

[SwampSurvivor]

Is this a vehicle that requires the front suspension to be completely disassembled or removed to drop the engine/trans cradle? I could see something not going back together exactly right causing an alignment issue.

Or something happened to a wheel bearing when they were trying to remove the CV shaft.

 

[penz08]

Is this a vehicle that requires the front suspension to be completely disassembled or removed to drop the engine/trans cradle? I could see something not going back together exactly right causing an alignment issue.

Or something happened to a wheel bearing when they were trying to remove the CV shaft.

I mentioned this to the alignment shop and they said they will check for the cradle during the alignment, surprisingly, it was not that off in the front wheels, the back wheels were still aligned from the last alignment I did 3 years ago. So yes they did check for this issue and it seems to be fine for the alignement.

 

[dadto2]

If my math is correct, you have 79,000 miles (127,000 km) on the tires? Time to replace them?

 

[Soft Cars]

They probably dropped the subframe / engine cradle when they pulled the transmission. There's usually some wiggle room when aligning the subframe with the body mount holes. If the subframe is not placed back in the exact orientation as it was from the factory, you can have wheel alignment issues that can't be corrected with a wheel alignment.

 

[penz08]

If my math is correct, you have 79,000 miles (127,000 km) on the tires? Time to replace them?

not exacly, a bit less because I am using winter tires for 3-4 months per year.

 

[penz08]

They probably dropped the subframe / engine cradle when they pulled the transmission. There's usually some wiggle room when aligning the subframe with the body mount holes. If the subframe is not placed back in the exact orientation as it was from the factory, you can have wheel alignment issues that can't be corrected with a wheel alignment.

okay, but the alignment shop told me they could check this out when aligning, it seems to go stray, however I am not 100% sure of that, I need to find a nice flat road surface to test it out, without wind.

 

[Soft Cars]

okay, but the alignment shop told me they could check this out when aligning, it seems to go stray, however I am not 100% sure of that, I need to find a nice flat road surface to test it out, without wind.

Does that mean you already knew about the potential alignment issue from the subframe?

 

[t1snwrbrdr12]

Even though you say it doesn’t sound like a wheel bearing, some cars are known to be super sensitive to over-torquing axle nuts which in turn trashes the wheel bearings. Very common to happen after a transmission job as they had to remove and reinstall this. And how it changes with steering and higher speeds goes along with a failed bearing.

 

[penz08]

Even though you say it doesn’t sound like a wheel bearing, some cars are known to be super sensitive to over-torquing axle nuts which in turn trashes the wheel bearings. Very common to happen after a transmission job as they had to remove and reinstall this. And how it changes with steering and higher speeds goes along with a failed bearing.

it could be very possible, I really doubt its the tires to be honest and wheel alignment, so that would be my guess as well.

 

[penz08]

Does that mean you already knew about the potential alignment issue from the subframe?

Well I knew there was something off when I drove it back home, they obviously removed the transmission, and everything attached to it.