[Gio72]

I confirm that for me it is absolutely normal

[HandlerFahrer]

I just bought a brand new 435i Gran Coupe M Sport. Just took it in - brand new I may add again, because of a whining noise at 42 and then again at 48. Tech rode with me and said he has heard this on cars in the past and that it is "normal". I also definitely hear a whining noise in reverse that you all are talking about. I thought it was the turbos for a while, but as I am getting used to the car I know this is actually some sort of gear noise so maybe it's from the transmission. I am driving a loaner (by chance a 535i) so it's another "35" car with 8 speed transmission. This car has the reverse whine as well, exactly like my car. To clarify it is not at high speed in reverse - probably 5-8 mph and if you hold the car steady at that speed with brake slightly on, it maintains the loud, steady whine with no problem. I guess it must be normal. The 48mph whine I'm not so ok with though. I'm going to test drive 3 435i cars and see if I can duplicate it in them. I'm pretty disappointed in buying a 65k car and have these types of noises. Hard to believe - these cars are supposed to be world class engineering. What is the deal?

[oceanview]

Whining in reverse cause explanation:
https://f30.bimmerpost.com/forums/sh...2&postcount=20

[pullinate]

Originally Posted by oceanview

Whining in reverse cause explanation:
https://f30.bimmerpost.com/forums/sh...2&postcount=20

There is one thing I really don't understand than:

My M235i whined in 1 and 2 gear, very loud. It was a 2016 built. Than my M240 whined in reverse, which was very loud and almost like a siren, it was a 2018 (!).
Also my wifes 220i - year 2017 - whines in reverse.
My brand new M340i also whines very slightly in reverse now.
All the cars I really owned were way newer than the mentoined 2014+ and all of them made some kind of whine.

So when and how did the changes happen?
I really don't see it to be honest.

Either they didn't change anything in the gearbox or the new design is making the same noises too.

[fredde85]

I have whine sound on reverse in my 428i 8AT

[Vinnief96]

Originally Posted by pullinate

There is one thing I really don't understand than:

My M235i whined in 1 and 2 gear, very loud. It was a 2016 built. Than my M240 whined in reverse, which was very loud and almost like a siren, it was a 2018 (!).
Also my wifes 220i - year 2017 - whines in reverse.
My brand new M340i also whines very slightly in reverse now.
All the cars I really owned were way newer than the mentoined 2014+ and all of them made some kind of whine.

So when and how did the changes happen?
I really don't see it to be honest.

Either they didn't change anything in the gearbox or the new design is making the same noises too.

Super old thread, lol. I have a 2015 335xi and it doesn't whine at all in reverse. 8AT

[alex0607]

This thread was dug up from a deep sleep. Lol!

Anyway, here is a good video on why the reverse gear whines. And its benefits in race cars and not in street cars.

But honestly all reverse gear whines whether its auto or manual.

[alex0607]

Originally Posted by Vinnief96

Super old thread, lol. I have a 2015 335xi and it doesn't whine at all in reverse. 8AT

Try to reverse and accelerate, you will hear the whine. At slow speed which we normally reverse at, I don't think its that audible. I know my F30 reverse does whine.

[Vinnief96]

Originally Posted by alex0607

Try to reverse and accelerate, you will hear the whine. At slow speed which we normally reverse at, I don't think its that audible. I know my F30 reverse does whine.

Mine absolutely doesn't whine at any speed in reverse. I'll try to post a video

[Vinnief96]

Originally Posted by alex0607

Try to reverse and accelerate, you will hear the whine. At slow speed which we normally reverse at, I don't think its that audible. I know my F30 reverse does whine.

I did however always hear a whine in my old Honda. That seemed to have stopped when I got a bmw in my current experience

[auburnf30x]

My 330i does have a slight whine in reverse, for the straight cut gear reason explained in this thread.

As to why some of us hear it loudly while others don't hear it at all, it is likely due to small, but allowable, variances during production. I have absolutely no idea what the gear spec is, but just say the factory specs for the tooth pitch is 0.50 inches with a tooth depth of the same. ZF will allow (again, purely a guess) the gear to pass inspection if the tooth pitch measures anywhere in the 0.49 - 0.51 inch range, and let's just say the same for the tooth depth as well.

Since straight cut gears make so much noise due to the teeth repeatedly clinking together on each pass, it is likely that those of us with gears on the larger end of the allowable spectrum will hear less noise, since the tolerances are tighter.

Either way, whine in reverse, no whine in reverse, completely normal. As long as your car is actually moving backwards in either scenario.

[Psi5]

I always wondered why those rental cars were *so* noisy when you drove them in reverse at 40 mph...

[oceanview]

Originally Posted by alex0607

This thread was dug up from a deep sleep. Lol!

Anyway, here is a good video on why the reverse gear whines. And its benefits in race cars and not in street cars.

But honestly all reverse gear whines whether its auto or manual.

That's true, but not for all.
BMW mechanical gear boxes already used helical rear gear wheels back in E30 3 Series. Why did they so? To avoide the whine in reverse! A comfort function!
It's a cost factor for manufacturing. That's why most manufacturers use/used straight gear wheels for reverse in manual gear boxes.
(See #2 and #26)
http://bmwfans.info/parts-catalog/E3...el_set_parts_2

The whine in the F30 with the ZF 8HP gearbox has another cause, as I wrote in my linked post.

[oceanview]

Originally Posted by pullinate

There is one thing I really don't understand than:

My M235i whined in 1 and 2 gear, very loud. It was a 2016 built. Than my M240 whined in reverse, which was very loud and almost like a siren, it was a 2018 (!).
Also my wifes 220i - year 2017 - whines in reverse.
My brand new M340i also whines very slightly in reverse now.
All the cars I really owned were way newer than the mentoined 2014+ and all of them made some kind of whine.

So when and how did the changes happen?
I really don't see it to be honest.

Either they didn't change anything in the gearbox or the new design is making the same noises too.

I don't know. That's just what the Service Manager at my ZF location told me. It's tha planetary gear set III which is causing the whine.
Here the PDF with the technical explanation in German
https://1drv.ms/b/s!AqdJMMUQxA-nwN49...5o8hw?e=xJa5fu

I don't know if it is just valid for the 8HP45.
Could be that other 8HP do whine as well in reverse, but not wiht the technical cause as in the 8HP45.

You can PM me the version you have in your car and I can try to ask him.