Accidentally forced into reverse gear 3 times while rolling backwards. All 3 had a half second grind. Not sure how bad this can possibly damage the reverse gear but hopefully not at all.

 

You will absolutely damage your gears. On a manual transmission, a special gear cog (reverse idler gear) that is separate from the two shafts containing the forward drive gears is used to reverse the forward rotation of the crankshaft (contained within the motor) so that your wheels spin backwards instead of forward. The countershaft which is permanently connected to the wheels must not be rotating to allow the reverse gear to lock in place. The grinding noise is the sound of the straight toothed reverse idler gear, riding over the top of the reverse gear on the counter shaft as it fails to engage since the later is turning.

Simply use your foot brake to stop the car before shifting into reverse. Unless you are on a very steep hill, a small amount of rolling is ok.


Comment: Absolutely constructive advise!!! This is educational input!!! - rttby

 

Since it was already in my photobucket, I figured I'd upload this picture just for fun. This is the inside of a GD3 manual transmission. The lone straight toothed gear on the bottom front of the picture is the reverse idler gear. On top of that gear is a little metal "finger" and there is another finger underneath the gear also so it is like a fork.

When shifting in reverse, the fork pushes the whole gear cog down so that it connects with the other straight toothed gear located on the gear shaft on the right (the countershaft) and the shaft on the left (mainshaft or inputshaft). Since these gears are straight toothed, if you are unlucky, the teeth might not line up well so shifting into reverse can occasionally be slightly difficult. Remember that the countershaft is always connected with the wheels (via the final driven gear, located on the bottom right of the pic with a number 8 stamped on it) and will be spinning whenever the wheels are spinning, even in neutral.

***note*** the GK is a six speed so the gear layout will be slightly different but the reverse gear is the same.

 

This is awesome, thanks for sharing! So why are the other gears angled but not reverse?

 

I had a Mini Cooper before my new fit, and I could shift into reverse while rolling, so it surprised me too when my transmission grinded as I tried to shift into reverse while rolling lol.

 

I can only guess the angled gears are meant for high speeds to make syncing easier.

 

The gear type is called "helical" and it offers a more gradual/smooth connection so it produces less noise than straight or saw toothed gears and is common in high speed situations for noise abatement. When lower speeds are envolved a saw tooth gear is used like in the case of this transmission. Apparently some older cars (like certain Lotus') used straight toothed gears even for forward gears so the car would produce the same whine we hear in reverse when going forward! Must have been a noisy ride!

 

Here's a view from the back. On the left there is the shift fork/collar for 1st and second, in the middle is 3rd and 4th and on the right it is fifth and reverse. You can see a little "finger" on the bottom of the right fork which pushes on the little fork mechanism (lower right) to engage the reverse gear. If you look carefully at the bottom of the mainshaft, you can see a very small straight toothed gear. That's the one that is used in reverse I believe. It is obviously small because you don't want to reverse at high RPMs! At least I don't want to. Maybe it's a mod for someone

You also have a better view of the differential on the complete left. The hole is for one of the axles.

 

Beautiful piece of engineering!! It's one of the reasons why I've been a Honda owner since 1991. Reliability is the main reason why I own a Honda. I've had other brands but nothing came close to what Honda can do.

Very happy to be a long time Honda fan.