Q: Crunch/Grind/Notch Gears

[TigerNSX]

I was driving yesterday and for the first time, I heard gears grinding when I downshifted from 4th to 2nd (with rev matching). The car was driven for about an hour before this happened, and going about 20 mph.

I did a search on this issue using the key word "Grind*", and found numerous posts on the grinding issues between 2nd to 3rd, but not from 3rd to 2nd or 4th to 2nd.

I also noticed many different descriptions of gear problems.

So here are my questions:

1) If I had a grinding problem from the 4th to 2nd w/ the rev matching, is it due to the worn synchros? It happened only once.

2) What is the difference between the terms, grinding and crunching? Also, what exactly does it mean when the gears are "notch"?

Thank you!

 

[nsxtasy]

1) If I had a grinding problem from the 4th to 2nd w/ the rev matching, is it due to the worn synchros? It happened only once.

It might, but it might not (and if it is, it's probably the hub selector that is worn, rather than the synchro).

However, unless it happens consistently, I wouldn't worry about it.

2) What is the difference between the terms, grinding and crunching?

AFAIK they describe the same phenomenon, when there is a sound and feel that are associated with those words, caused by gears that are not meshing smoothly. It sounds and feels rough.

Also, what exactly does it mean when the gears are "notch"?

Notchy gears are different from grinding and crunching. This is a phenomenon felt primarily in the shift knob. When the gear is notchy, instead of the knob sliding smoothly into gear, it meets resistance, and feels as though you have to move it into precisely one spot (a "notch") to meet that resistance.

 

[TigerNSX]

Thank you so much for your help and time, Ken!

It all makes sense!

 

[Joel]

Thank you so much for your help and time, Ken!

It all makes sense!

One often finds enlightenment after speaking with Ken.
I wonder if he has a degree in Divinity?!

Tell us, Ken, what is the meaning of life? Ha ha ha

 

[grippgoat]

Synchros still have to do work with rev-matching. Rev-matching just makes clutch engagement smoother. If you want to save work on the synchros, you have to double-clutch. Whether you need to / should save work on the synchros is another question.

I only ever double clutch doing a lazy 2->1 downshift, like if I was coasting down to a light and was nearly stopped, but then the light changed or something.

-Mike

 

[nsxtasy]

Tell us, Ken, what is the meaning of life?

Get in your NSX and take it for a long drive, and you will discover the answer to your question.