grinding gears

[toby19]

my mom always grinds the gears when she drives. what is actually happening (why grinding noise) and what damage does it do?

[KebabMeister]

The gearbox is on the side of the engine.  Between the engine and gearbox is the clutch.  When you press the clutch pedal you are disengaging drive between the engine and the gearbox.  If the clutch pedal operation is mistimed or not fully depressed whilst changing gear then you will 'grind' the gears.

As mentioned, there are two shafts of gears in the gearbox.  Each gear already has a baulk ring to help slow the gear down and engage (the gear level selects the gear).  If the clutch isn't depressed properly then these gears are engaging at a higher speed than designed and cannot locate the teeth.

[Clanad]

Ummm... not quite, but check here for an animated discription, including a syncromesh transmission...

http://auto.howstuffworks.com/transmission4.htm

[KebabMeister]

Clanad, what's not quite?  That's how they worked when I used to take them apart?  (in simplified terms of course)

[KebabMeister]

Okay, the diagram you posted shows a very basic design without syncromesh.  The collar on the diagram is more often referred to the syncromesh sleeve which slides onto the baulk ring (copper sleeve) which is attached to the corresponding mainshaft gear.

Some good images here http://www.colin99.co.uk/celica/TOYOTA%20%20GEARBOX.JPG and http://www.smallfordspares.co.uk/diagrams/plate112.gif

[acw]

Are you all lads in this thread?  You all seem to have the bit between your teeth! Teehee!!  And Toby is nowhere to be seen! 

 

My answer is (girly non-mechanic answer coming up folks) : anything that makes the car make a bad noise can't be good.  This includes scraping noises when parking and that awful crunch when you drive your Mum's car slightly into the back of your Dad's car!  The worse the noise, the bigger the bill at the garage too. 

 

See - to the point and totally accurate! :-p

[KebabMeister]

hehe acw, that makes more sense!  screach, crunch, crash is not good noises! :)

[Clanad]

KebabMeister, my purpose was to correct the misnconception that the gear teeth actually disnegaged during shifting... that point was left unclear.  BTW, the syncromesh  transmission is discussed and demonstrated on the third page of the link I posted.  In the US, the clutch/tranmission assembly is on the rear of the engine in rear wheel drive cars and light trucks... Thanks for you expertise!

[KebabMeister]

Clanad, I'm so used to working on front wheel drive engines I automatically say the gearbox is on the side of the engine... but it depends on how you look at the engine I guess?! :)  Rear wheel drive, front engined cars, are not too common in the UK (mostly reserved for more upmarket cars like BMW, Mercedes, Jaguar, sports cars etc.)