Car is a 97 Civic HX with 178k. When I push in the clutch, there is a terrible mechanical grinding noise. Whats strange, is that everytime I push in the clutch while driving at speed, speedometer drops to 0.

Only thing I can think of is whatever the VSS drives off, is moving when clutch is depressed??

 

I don't know about the speedo, but noise when the car is in neutral with the engine running is typically a damaged input gear bearing, or clutch release bearing (throwout bearing)

 

It's usually a bad clutch throw out bearing if you hear the noise only with the clutch pedal depressed. I'm struggling to make sense of the speedometer problem though. Any CEL codes?

 

As am I

 

I'm wondering if his vss is loose and when the pressure is relieved it slids out of contact

 

I'm not sure what you mean by pressure relief because, when the car is moving, the differential turns the VSS regardless of whether the clutch is depressed or not.

 

I'm just trying to think of a way they could be connected. When you have the clutch engaged there's more pressure against the diff. When you press the pedal in the diff still spins but its coasting.

 

If the bearings in the transmission or throw out bearing is Seized it would make the speedometer drop to zero. its like pushing your skate board with seized bearings, it will still move if your pushing it, it will just stop quicker or stop right away....

 

its simple really, your moving so the axles are turning even with the car in neutral so thus the transmission is turning so the speedo will be.

 

so got any idea why it stops reading when he pushes in the clutch?

 

the trans is completely ****ed and i bet his speedo gear on the differential is slipping

 

just pick up a d series trans there a dime a dozen

 

I don't think this is possible.

 

It's not.

The diff has the speedo gear pressed onto the carrier. As long as the car is moving (either under it's own power or rolling) the diff is turning and so is the speedo gear. Which is what makes this so hard to wrap my head around.

 

Or it is very possible. I have a ls trans in my wagon. The speedometers didn't work abelow 60mph and i was going faster than 60 on my gps. I swapped vss nothing. And so I pulled the trans apart. Turned out my CSS gear pressed on the diff was just chillin there so yes its VERY possible

 

The car would not move if that was the case-

I ended up turning the car off, wiggling the VSS to ensure it was tight (it was), checked for leaks at clutch slave, verified fluid, and started it back up with no issues. I drove it 100 miles and no signs of the sound coming back.


I guess guess the only thing I can think of is wherever the VSS drives off, began to strip ( I will pull it this weekend to check the teeth). What made it strip is beyond me. Can anyone who knows internals of a D series transmission enlighten me how the VSS meshes with the differential, and what play is available if something were to bad?

 

Plastic helical gear on the VSS meshes with a plastic gear pressed on the differential carrier.

 

Thank you!

the speedometer still works- I would expect it to wear down all the plastic resulting in no speed reading.


Now the question is what was causing either the differential or the VSS to move when the clutch was depressed? This happened at speed and stationary.

I could understand if it was from load, but when stationary there isnt any load on teh differential.

 

anyone else?

 

Obviously, when the car is stationary, the speedometer should not register any speed. The speedometer would register speed when the car is stationary only if an axle has popped out of the differential and you rev the engine with the transmission in gear. But in this case the car would not move.

 

Good point, if the noise was the VSS/ final drive gear stripping, how would it happen when stationary?

But on that same note, why would the VSS drop when in motion?