Dumb question on transmission

[Sub-Vibe-R]

Anyone here know why the sound of a manual tranny while backing up is different then an auto tranny.Where does come from this specific sound?

[NovaResource]

quote:Anyone here know why the sound of a manual tranny while backing up is different then an auto tranny.Where does come from this specific sound?How do you mean? The reverse beeper of the 6-speed or the gear whine?

[Sub-Vibe-R]

quote:Anyone here know why the sound of a manual tranny while backing up is different then an auto tranny.Where does come from this specific sound?How do you mean? The reverse beeper of the 6-speed or the gear whine?The gear whine... the ZZZZZ sound when you're backing up with a car with a manual tranny that you don't have with an auto tranny

[Frosty]

Sub is talking of the straight cut, non sychromesh reverse gear noise. Reminds me of a tow truck in what we used to call bull or creeper low. Can anyone elaborate?

[Lorin]

ZZZZZ ...... errr errrr...... Anyone else care to help reproduce the sound! LOL! ok, here's what mine sounds like: errrrrrrrrRRRRR!!!!!

[Sub-Vibe-R]

quote:ZZZZZ ...... errr errrr...... Anyone else care to help reproduce the sound! LOL! ok, here's what mine sounds like: errrrrrrrrRRRRR!!!!! Exactly this freaking sound when you're backing up! Where it come from?

[robdog]

Reverse is a very high gear and it is just whining out. It is like when you put a 4WD in low range. It sounds the same.

[piffy]

All this is well and good, but why don't you hear it as much in an auto-tranny. There is a distinct difference in the sound between an auto and manual.Do they have different gearings? Different construction?

[NovaResource]

Manual transmissions use mostly helical gears for the forward ratios. These gears have teeth that are cut on angles and are very quiet. However, the reverse gear is a different because it changes the direction of the output shaft. This requires a different type of gear called a spur gear. Spur gears have teeth that are cut straight and it's these straight-cut teeth that make the noise (not the ratio).In the picture above, the gears with angles teeth are the forward gears, the ones with straight teeth are reverse gears.quote:All this is well and good, but why don't you hear it as much in an auto-tranny. There is a distinct difference in the sound between an auto and manual. Do they have different gearings? Different construction?Yes, automatics use what are called "planetary" gears. One "sun" gear in the center, multiple "planet" gears (usually 3 but it could be more) around the sun and a "ring" gear around the "planet" gears. The planet gears can rotate on their own axis or sometimes they also rotate around the sun gear. Gear changes in an automatic don't physicaly move the gears but instead stop gears from moving or start gears moving.Planetary gears look something like this:Here is some good info to read if you are more interested:http://auto.howstuffworks.com/automatic ... ission.htm

[QUIKAG]

You're wrong, Nova!! JUST KIDDING!! Good informative post.

[pmh013]

Wow, Nova! That's a lot of awesome information ... is the gear photo from our Vibes?I howstuffworks.com. I work in one of those places where someone is always asking questions that no one knows the answers to -- that website really helps!

[NovaResource]

That gear pic is from the HowStuffWorks.com webpage. I don't know what transmission that is a pic of.