I am new with 5spd, so there are times when i switch the gears from 2nd to 3rd and i hear this loud grinding sound like i got it into the wrong spot. It happened around 3 time so far. Please tell me how serious it. because i get so crazy about it that it feels like it doesnt work righ even though it probably does.

 

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Make sure your clutch is all the way down during the entire shift. It happens to me when I start letting the clutch out slightly before I actually get it into the next gear...

-V

 

It's your synchros! Get Daniel B to give you the technical explanation.

Simply: Synchros match the speeds of the moving parts in the transmission. Synchros wear excessively from high RPM downshifts. I recommend people learn how to double clutch downshift. This allows the engine speed and transmission speed to synch before you shift. This allows a shift that is silky smooth (no effort require to get into the gate). Also, if you ever noticed that it's hard to downshift into first when moving, that's your synchros working. If you double clutch you can see how easy it is to get the car into first gear even if you're going 25+ MPH.

Wait for Daniel B Martin's explanation. I know a lot about cars, but he's got the books and the experience.

I am almost positive it's synchro's though.

 

Dave explain what you mean by Double clutch as well as u can

TX

 

That ugly grinding sound is called Gear Clash. It may be caused by ...
- driver error (clutch pedal not all the way down)
- driver error (shifting too slowly... a good shift is Click-Click, rapid but not forced)
- dragging clutch (physical damage)
- bad pilot bearing
- defect in hydraulic actuator (inadequate fluid, leakage)
- wrong amount or wrong quality of transmission lubricant
- worn transmission sychronizer

If your symptom appears only when doing the 2-3 shift, the Spotlight Of Suspicion falls on the synchronizer mechanism. A worn synchro typically results from high mileage or abusive driving.

 

BrianV's description of the purpose of the gear synchronizer is correct.

When you change gears you are causing the transmission to physically connect rotating components which are spinning at different speeds. The synchronizers inside the transaxle are speed-matching mechanisms which work by friction. When the components which you are seeking to couple are rotating at almost the same speed, the synchronizers have no trouble doing their job. If you hold the clutch pedal down and shift slowly the rotating components start to slow down, but they don't all slow down at the same rate. Remember that the differential is connected to the wheels, and as long as the vehicle is moving some of the transaxle components are also moving. A slow shift increases the burden on the synchronizers. The "best" shift (in terms of transmission wear) is CLICK-CLICK... rapid but not forced. Likewise, a forced fast shift (such as when racing) increases the burden on the synchronizers.

Go to http://users.erols.com/elans4/Transmission.htm and scroll down to Figure 14, Synchronizing Mechanism. This photo depicts part of an ancient Chevrolet 3-speed manual transmission but the basic elements of a gear synchronizer are the same. Note the Synchronizer Ring (item 7) has a plurality of small teeth (item 4) arranged around its periphery. Those teeth rarely break but they do wear with normal use, and wear quickly when subjected to abuse. When you hear that ugly sound we call "gears grinding" it is actually a cry of pain from synchronizer ring teeth (item 4) and their corresponding gear synchronizer teeth as they are being worn and chipped. The gear synchronizer teeth are not item-numbered, but you can see them as part of the gear (item 5). The gear synchronizer teeth are clearly pictured in Figure 17, Synchronizer Operation.

 

Double clutching means performing every gear change as two distinct changes. If you were shifting to a higher gear (such as from 2nd to 3rd) you would shift from 2nd to Neutral and then shift from Neutral to 3rd. You would let the clutch pedal up while in Neutral.

If you were shifting to a lower gear (such as from 3rd to 2nd) you would "blip" the throttle to bring up engine speed while in Neutral. This eases the burden on the transmission synchronizers.

Many years ago car transmissions did not have the Synchromesh feature and double clutching was required. Even today, big trucks are double clutched.

For more information about double clutching, go to
http://integra.vtec.net/driving/dclutch.html
http://www.driversedge.com/dblcltch.htm

 

Yeah Daniel B's right on the double clutch

Simply it's being in third gear. Shifting to neutral. Letting off the clutch. Revving the gas up, and clutching in and sliding into 2nd. The idea is to blip the throttle to the right engine speed so the synchro's don't have to do their job. This all comes in time and practice. You just get a feel for the car.

Also, when racing you can heal-toe brake. Heal-toe is essentially performing a double clutch, while operating the brake at the same time. Thus, using three pedals at the same time with two feet. You manipulate your right leg to control both the gas and the brake at the same time. Once you learn how to straight double clutch you can try heal-toe. I can do both double clutch and heal toe without thinking about it (second nature).

DISCLAIMER - when double clutching your car makes a quick, loud, rev noise. Many people think you're actually revving on them, but they're just stupid. Many times I've had other people try and start crap, "Man why you gotta rev on me"

I look over and see some fool in an IS300 and reply, "Well if you drove stick maybe you'd know I was simply double clutching"

So be careful, some people take it as revving.

 

You could try all those things that the other have suggested, however, I can suggest something that may be a bit easier. I find that, when driving in a leisurely fashion, shift from 1st to 2nd slowly, i.e. give the synchros more time to synch up. Then, when going from 2nd to 3rd, 3rd to 4th, 4th to 5th, shift relatively quickly. When I say quickly, I mean that the time between pushing the clutch, changing the gear, and letting off of the clutch is very short. The spacing between gears 2,3,4, and 5 is such that you have little time before the synchros lose synch, so to speak.

DW

 

According to the history of Cadillac found at http://vintagecars.about.com/autos/v...y/aa072598.htm ...

Another Cadillac first was the synchromesh transmission in 1929. Now drivers didn’t have to double clutch to avoid grinding gears.

 

Sorry to sound like im just so uninformed but Im just trying to get a visual...So Brian why do you need to heel toe...and brake while racing...what function does the brake perform? Or is that to simply come out of first gear...thanks in advance for the info...

 

Here's some really good info on heel-toe. It's a link from Cheston's www.maximadriver.com how-2 section.

http://www.turnfast.com/tech_driving..._heeltoe.lasso

 

You should keep in mind that the standard Maxima pedals makes heel n toe very difficult. You should get a set of those aftermarket fatter pedals if you want to really get into heel n toe action with your car.

DW

 

I do NOT have very long legs, and even with the seat all the way back, I can't get into position to heel-toe. I've been unable to find a way to turn my right foot left and keep my knee out of the steering column.

 

you guys are killing the poor boy with all this information

bring that baby up to waterbury and i will show you how to bang some gears

 

The point in heal toe downshifting/braking is that if mastered you can brake and downshift at the same time which thus slows the car down faster. When racing you want to slow down fast and at the last possible moment. If you brake then downshift you've wasted too much time.

 

Aren't you down in Atlanta?

 

I'm not trying to be a ****, man, but the thing on the bottom of your foot is your HEEL. HEAL is what it does when you cut it and put on a bandaid.

 

 

You got that right , i dont even know half of the things they are talking about. And i still didnt get the info if my mistake of grinding from 2 to 3 is really bad at like 2000rpm. Thanks

 

No, it's not really bad.

 

Thanks,I will go catch up on my sleep now that I know it wasnt that bad.