Why do cars in reverse sound different?

[CTho9305]

see topic

 

[Eli]

Reverse typically uses a very tall gear, so you hear the "whine" you hear is gear whine.

 

[NeoPTLD]

Originally posted by: CTho9305
see topic

The sound is probably coming from transmission, but yeah I see what you're talking about. You can tell someone's backing up if they're going relatively fast without even looking at it.

 

[feralkid]

It is because the reverse gear itself is not beveled or is it "hypoid"? In the olden days before bevel gears, cars made the same noise you are hearing in all forward gears as well. What it looks like is the teeth are cut 'at an angle' which makes them operate much smoother and therefore quieter.

 

[5LiterMustang]

It's the steeper gearing of the tranny. Generally reverse gears are between 1/2 and 3/4 of what first gear is. Makes noises in the drivetrain more audible.

 

[NeoPTLD]

Originally posted by: 5LiterMustang
It's the steeper gearing of the tranny. Generally reverse gears are between 1/2 and 3/4 of what first gear is. Makes noises in the drivetrain more audible.

Harness teh power of reverse gear with a bad ass burn out LOL

 

[Eli]

Originally posted by: feralkid
It is because the reverse gear itself is not beveled or "hypoid". In the olden days before bevel gears, cars made the same noise you are hearing in all forward gears as well.

Hmm. Interesting.

I was going to say there might be another reason, because reverse is typically only a little taller than 1st, but 1st doesen't make the same gear whine noises that reverse does...

On another note, the 3 speed manual in my Dad's 1/2ton Chevy PU has a distinct whine in all gears, but especially in reverse.

 

[AgaBoogaBoo]

Why wouldn't they use the same ratio as first gear? IT could be slightly taller, but is there a real need for it? I mean, how mcuh use it during a turn?

 

[feralkid]

Originally posted by: AgaBooga
Why wouldn't they use the same ratio as first gear? IT could be slightly taller, but is there a real need for it? I mean, how mcuh use it during a turn?

They generally do...the "tall"explanation is mistaken.

 

[Eli]

Originally posted by: feralkid

Originally posted by: AgaBooga
Why wouldn't they use the same ratio as first gear? IT could be slightly taller, but is there a real need for it? I mean, how mcuh use it during a turn?

They generally do...the "tall"explanation is mistaken.

Whatcha mean?

Yeah. From what I've seen, it is usually slightly (like 0.25:1) higher than 1st.

 

[NeoPTLD]

I guess the ratio of reverse gear depends on transmisson:

European MAZDA Demio 1.31
Drive Train Transmission Type 5MT
Gear ratios lst gear 3.416
2nd gear 1.842
3rd gear 1.29
4th gear 0.972
5th gear 0.82
Reverse gear 3.214(shorter than first)

1989 to 1992 Lancia Thema(From a Dutch website)
first Gear Ratio3.500
Second Gear Ratio 2.312
Third Gear Ratio 1.523
Fourth Gear Ratio 1.156
Fifth Gear Ratio 0.917
Reverse Gear Ratio 3.583 (taller than first)

 

[PowerMacG5]

Originally posted by: NeoPTLD

Originally posted by: 5LiterMustang
It's the steeper gearing of the tranny. Generally reverse gears are between 1/2 and 3/4 of what first gear is. Makes noises in the drivetrain more audible.

Harness teh power of reverse gear with a bad ass burn out LOL

I can do a burn out at will in my car in reverse, but forward I gotta try like a motherfvcker to get the wheels to spin. I need a new torque converter .

 

[feralkid]

Originally posted by: Eli

Originally posted by: feralkid

Originally posted by: AgaBooga
Why wouldn't they use the same ratio as first gear? IT could be slightly taller, but is there a real need for it? I mean, how mcuh use it during a turn?

They generally do...the "tall"explanation is mistaken.

Whatcha mean?

Yeah. From what I've seen, it is usually slightly (like 0.25:1) higher than 1st.

The 'ratio' can be different, i guess...What i mean is they share the same..laygear?...I'm a little rusty here, so let me go double check.

 

[Demon-Xanth]

NV3500 1st gear: 4.01 Reverse: 3.55

The noise is caused because there's an extra gear that's being turned, instead of two gears meshing directly there is a gear between them to get the shafts to turn differently than in straight forward gears.

 

[GalvanizedYankee]

The reverse gear probably is not fitted or meshed as well as first, on most transmissions it sits off to the side. Its not used in anger as first is so it never takes a
match to its mate.

Most reverse noise I hear comes from the differential. It is not meant to turn in that direction. Old Chev rear ends howl as if its their sig..............

 

[feralkid]

Originally posted by: Demon-Xanth
NV3500 1st gear: 4.01 Reverse: 3.55

The noise is caused because there's an extra gear that's being turned, instead of two gears meshing directly there is a gear between them to get the shafts to turn differently than in straight forward gears.

Thanks, that's what I was trying to remember. In a lot of cases, the reverse gear is on its own layshaft...with a gear on each end...one is hypoid, the other is not. That's where the noise comes from. Of course there are many variations...and I'm pretty much thinking of mid 60's British cars here, which i'm sure the OP was not.

.

 

[Sluggo]

Originally posted by: feralkid
It is because the reverse gear itself is not beveled or is it "hypoid"? In the olden days before bevel gears, cars made the same noise you are hearing in all forward gears as well. What it looks like is the teeth are cut 'at an angle' which makes them operate much smoother and therefore quieter.

Da winnar

Reverse gear, due to the lack of speed needed and the fact that they dont need to be helical cut since you are generally stopped when shifting into reverse, is a straight cut gear.

More information than you ever wanted to know about gears Only site I could find doing a quick search that had pics of both

 

[marquee]

duh
because a car going forward goes "vroom vroom" and a car going backwards goes "moorv moorv"
hasn't anyone ever read 'the mouse and the motorcycle'?

 

[ThisIsMatt]

Straight cut gear.

 

[Vic]

The reverse gear is "straight cut" or not a helical cut gear like the others. That accounts for some of the whine. The other part is that there is a counter or "idler" gear inbetween the gears that is also straight cut -- the addition of this 3rd gear is what makes the drivetrain spin in reverse.

 

[CTho9305]

Originally posted by: marquee
duh
because a car going forward goes "vroom vroom" and a car going backwards goes "moorv moorv"
hasn't anyone ever read 'the mouse and the motorcycle'?

haha yea i remember that

Thanks to the rest for answers.

 

[sharkeeper]

It is because the reverse gear itself is not beveled or is it "hypoid"? In the olden days before bevel gears, cars made the same noise you are hearing in all forward gears as well. What it looks like is the teeth are cut 'at an angle' which makes them operate much smoother and therefore quieter.

Nice!

You can hear forward sounding like reverse in this example.

Cheers!