OT: Clutch in 5th gear

[d_man16]

I've had the same car for about two years and I've gotten to the point where I can slip the shift lever into 5th w/o using the clutch on the highway. It doesn't grind or anything but it leaves me wondering am I harming the tranny by doing this?

[RPS]

Probably. In theory you can argue that if you matched RPMs exactly that no harm is done, but just because you can’t feel or hear any grinding doesn’t mean that you are not causing additional wear. I wouldn’t do it.

[Mike748]

No. If it goes in clean then everything is turning at the same rpm. Any noise indicates you are causing wear. I used to have a VW Rabbit and a TR4 that I could shift through all the gears without the clutch. Only needed it to get the car moving. But remember that clutches are cheap, gearboxes aren't.

[Ralph]

No. If it goes in clean then everything is turning at the same rpm. Any noise indicates you are causing wear. I used to have a VW Rabbit and a TR4 that I could shift through all the gears without the clutch. Only needed it to get the car moving. But remember that clutches are cheap, gearboxes aren't.

I agree.

[AngryScientist]

this technique is called "slip shifting". its fine if you're doing it right, but not a good habit to get into, there is usually at least a little speed/momentum difference, which can cause wear. use the clutch brother.

[Mark McM]

No. If it goes in clean then everything is turning at the same rpm. Any noise indicates you are causing wear. I used to have a VW Rabbit and a TR4 that I could shift through all the gears without the clutch. Only needed it to get the car moving. But remember that clutches are cheap, gearboxes aren't.

I'm not sure I completely agree with this. Clean engagement in manual transmissions relys on the syncros. When shifting without disengaging the transmission with the clutch the syncros are operating under a heavier load, and can wear out faster. It is true that modern synchros allow the transmission to be shifted through all the gears without using the clutch, but that doesn't mean that it doesn't cause any wear and tear in the transmission (even if it quite). As Mike748 says, the clutch is intended to be the sacrificial element, not the syncros.

[Ken Robb]

Your transmission has synchronizer rings and their job is to get the non-turning gear that you want to engage to spin up to the same speed as the driven gear so they "syncromesh" when they come together. Think of them as mini-clutches and like all clutches they wear at least a little with every use. Anything a driver can do to ease the engagement of the synchronizers will extend their life. Shifting slowly is the easiest way to be nice to your transmission synchros. Changing your transmission fluid every 30,000 miles is a very good thing and you will be amazed how that improves your shift action. Skillful double-clutch downshifting also helps the synchros but increases wear in your clutch so that's a questionable practice in most situations. I do it because I learned to drive in some old cars with very weak synchros in 2nd and 3rd gears and none in 1st so double clutching was the best way to drive.

I wouldn't drive a normal car without using the clutch to shift because it will hurt it in the long run.

Hmmmm, I see that while I was writing this Mark covered it pretty well first.

[Mike748]

I'm not sure I completely agree with this. Clean engagement in manual transmissions relys on the syncros. When shifting without disengaging the transmission with the clutch the syncros are operating under a heavier load, and can wear out faster. It is true that modern synchros allow the transmission to be shifted through all the gears without using the clutch, but that doesn't mean that it doesn't cause any wear and tear in the transmission (even if it quite). As Mike748 says, the clutch is intended to be the sacrificial element, not the syncros.


Don't quite agree with the synchro load idea. Clutch engaged, the engine is driving the input shaft of the gearbox, the wheels are driving the output shaft. If both are spinning at the correct rpm for one of the gear rations (lets say identical speed, 1:1 4th gear) then it will go into that gear without any effort from the syncros. If the speeds are mismatched, the synchro won't be able to match them... they are sized to slow a rotating shaft not an engine or a car. So then you will grind the engagement cogs and it will go into gear with a jerk and excess wear will result.

Motorcycle gearboxes don't use synchros because the rotating mass is so small. They use engagement dogs. Very easy to shift without the clutch because the really won't go into gear until speeds are correct.

[130R]

The clutch is there for a reason m8.

[RPS]

Don't quite agree with the synchro load idea. Clutch engaged, the engine is driving the input shaft of the gearbox, the wheels are driving the output shaft. If both are spinning at the correct rpm for one of the gear rations (lets say identical speed, 1:1 4th gear) then it will go into that gear without any effort from the syncros. If the speeds are mismatched, the synchro won't be able to match them... they are sized to slow a rotating shaft not an engine or a car. So then you will grind the engagement cogs and it will go into gear with a jerk and excess wear will result.

Motorcycle gearboxes don't use synchros because the rotating mass is so small. They use engagement dogs. Very easy to shift without the clutch because the really won't go into gear until speeds are correct.
In my engineering opinion it’s not that black and white and either speeds match or they don’t. It’s not that simple. Just like the synchronizers can engage a transmission with a much higher speed difference when using the clutch because of very low rotating mass, they can also engage much heavier mass when differential speeds are lower. This doesn’t imply that the speeds are exact by any means at all. One could be rotating at 3,000 RPM and the other at 3,005 RPM and the driver can still engage the selected gear by allowing the synchronizer to do its job. In the process you’ll create more wear than if the clutch was used. Ideally to minimize wear the driver should try to match speeds somewhat closely “and” use the clutch.

As I stated before, if the speeds were both exactly matched at 3,000 RPM or whatever, then it can be argued that no incremental wear is added. However, matching anything exactly most of the time is a statistical impossibility. Just because you can’t hear grinding doesn’t mean the synchronizers aren’t being asked to do more than what they were designed to do.

[Mike748]

In my engineering opinion it’s not that black and white and either speeds match or they don’t. It’s not that simple. Just like the synchronizers can engage a transmission with a much higher speed difference when using the clutch because of very low rotating mass, they can also engage much heavier mass when differential speeds are lower. This doesn’t imply that the speeds are exact by any means at all. One could be rotating at 3,000 RPM and the other at 3,005 RPM and the driver can still engage the selected gear by allowing the synchronizer to do its job. In the process you’ll create more wear than if the clutch was used. Ideally to minimize wear the driver should try to match speeds somewhat closely “and” use the clutch.

As I stated before, if the speeds were both exactly matched at 3,000 RPM or whatever, then it can be argued that no incremental wear is added. However, matching anything exactly most of the time is a statistical impossibility. Just because you can’t hear grinding doesn’t mean the synchronizers aren’t being asked to do more than what they were designed to do.

I fully agree with you.

BTW, Porsche syncros like a little bit more rpm differential to work properly than Borg Warner synchros.

[J.Greene]

I'll let the next owner worry about getting 200,000 or 250,000 miles out of the transmission.

[gemship]

Interesting this topic was brought up. My 2006 chevy silverado 1500 with the v6 and 5 speed was behaving very badly in regard to shifting. Basically it was nearly impossible to shift often times in first and reverse gears at a dead stop, didn't matter if it was from a cold start first thing in a winter morning or a summer morning or even during twenty minutes of driving. Then I started to have a hard time shifting into second gear. Numerous times with the clutch pedal to the floor it would even give a good ole gear grinds and slight vibration thru the shift stick on any given gear shift especially from first to second or second to third or into reverse once in a while from a dead stop. I will add I never had problems to this extent with either a 93" VW Fox or a 00" Tundra and both of those vehicles never needed clutch service and were second hand just like my Chevy. I finally decided to take the truck to a mechanic, his opinion was to replace the slave cylinder just because in the tranny(not leaking fluid) and do a straight forward clutch replacement mostly because there was a slight noise or hum from the throwout bearing, mind you no clutch slippage when accelerating in any gear. The fix wasn't going to be cheap to the tune of 1,200$. I took it to another mechanic who offered to do the clutch replacement for 895$ so I went ahead with the cheaper price. Anyway I get the truck back, just in time to start my new job, after two years of unemployment, victim of this economy I am. The third time I drove the truck after the repair was to the new job which was a long 40 min. , 22 mile commute from home. About a half hour into the commute I started having the same problem with the truck being very difficult to shift in the first three gears and I am a gentle driver, doing like Ken Robb describes in a earlier post of shifting slowly, using clutch, even matching road speed to engine speed to a reasonable extent. After the second night of work, yeah the job was terrible hours, second shift 3pm to midnight, I decided time to take it back to the mechanic. Turns out the tranny fluid was the culprit. It took a couple days to figure it out and a couple of mechanics as they were shaking their head and hesitant to drop the tranny again on their dime. My best guess is that the fluid was never changed on this 54,000 mile truck. I was told that it had a lot of metal grindings stuck to the magnetic drain plug. So almost like magic the truck is shifting better than the day I bought it with 49K miles however the supervisor at my new job was very strict and non sympathetic, I lost the job for being out of work due to this issue on my third day of work.This all happened less than a month ago. I read somewhere that transmission fluid is more than a lubricant, it's also a hydraulic agent, I told a buddy who is a genius backyard mechanic all this and he just couldn't believe it and proceeded to tell me that I probably need a new transmission but it's been a couple weeks and several drives since the fluid change and I haven't grinded a gear once nor had trouble shifting into gear, I am very lucky I feel to not have to replace/rebuild the transmission but I will change that fluid every 30K.


I'm even considering changing out the rear differential fluid, I used to always think this stuff was good for a 100k or the life of the vehicle but it actually isn't, I mean it's not on the frequency of engine oil changes but it is still critical maintenance unless your just leasing vehicles or sell them after so many miles.

[benb]

Aren't there additional differences in a motorcycle transmission that make this possible besides just the lighter mass and lack of synchros?

I had always read this was easier to do this properly on a manual transmission that did not have synchros, but I've never actually driven a car without syncros..

I do it on a rare occasion on my motorcycle.. it's mostly pointless since motorcycles shift so fast compared to a car anyway, even at the race track.. (Maybe it is significant at a drag strip, it's really not on a road course until you're at a very very high level.)

I've fiddled with it on my car(s) but they never really seem to like it so I haven't bothered trying to learn it.

[gemship]

Aren't there additional differences in a motorcycle transmission that make this possible besides just the lighter mass and lack of synchros?

I had always read this was easier to do this properly on a manual transmission that did not have synchros, but I've never actually driven a car without syncros..

I do it on a rare occasion on my motorcycle.. it's mostly pointless since motorcycles shift so fast compared to a car anyway, even at the race track.. (Maybe it is significant at a drag strip, it's really not on a road course until you're at a very very high level.)

I've fiddled with it on my car(s) but they never really seem to like it so I haven't bothered trying to learn it.


Well I'm no expert but ever since the situation with my truck I was told that some truck drivers do shift without the clutch and some of the heavier duty chevy trucks are built without the synchros, the designers even anticipated complaints from consumers and would suggest to try shifting without the clutch on non synchro transmission once the truck was moving, sounds crazy but it's what I heard.

[Ti Designs]

There's this technique called double clutching where you take it out of gear, match speeds and then put it back in gear. It's an odd dance step which involves stabbing at the clutch and blipping the throttle, sometimes while standing on the brake with the other side of your foot. (some people call this heal & toe, but my leg don't twist that way and there's a rev limiter switch on the left side of my throttle). As you get good at it you start to realize that all that stabbing at the clutch doesn't need to happen, as long as you catch a gear while the tach is on it's way down it all works. There is probably more wear on the gears by doing this, but which part of a car isn't wearing?

[christian]

Benb - The difference between mc and car transmissions, primarily, is that bikes don't have syncros, but use dog engagement. Many race cars too. Problem is, when the dogs wear, you have to rebuild the transmission. Fine for a race car every three events. Less practical in a car on the street. Motorbikes have very little dog wear due to the small rotational mass in the mc gearbox.

Other than that, no real differences. Bikes* have a wet clutch, which is another difference in the drivetrain, but not relevant here.

* Horrid tractor-looking BMW shaft-jobbies not included.

[benb]

Heel and Toe is not the same as double clutching, etc.. I've spent time trying to learn Heel-And-Toe but like shifting a motorcycle without the clutch it is 99% pointless on the street as far as I can tell. There's just no reason to "charge" a corner that hard when driving at anything even vaguely near legal speeds. Same thing with double clutching.. tried that just to give it a shot (it supposedly saves the syncros) but it's pretty slow. I'm guessing double clutching and clutchless shifts are probably much easier on large trucks with a lot of flywheel mass. My car is so eager to gain/lose revs that you're talking about split second timing.

I am not sure why there is even any debate over shifting without the clutch.. it sure as hell is not faster on anything modern. What does it accomplish other then being a useful skill if your clutch breaks?

Christian how can you complain about BMW bike transmissions and not mention the H-Ds and other bikes which are even worse? :p

[RPS]

Same thing with double clutching.. tried that just to give it a shot (it supposedly saves the syncros) but it's pretty slow.
Correct. Double clutching is most useful when driving transmissions which don't have syncros or don't have them on all gears. Not that long ago many car transmissions didn't have syncros in 1st gear or reverse, so in order to get a car in gear while stopped without grinding you opened the clutch and waited a second or two until the gearbox stopped rotating -- or came very close to it -- and then slipped it into gear. If in a hurry you could do it faster but it didn’t sound great. Today you can put most cars in gear while rolling in the opposite direction at low speeds without any problems -- and in those instances double clutching can't help since you can’t make the transmission reverse direction. I still have one to remind me.

The only time I found it useful in real-world driving was when downshifting into a non-syncro 1st gear to climb a steep hill or driveway and didn't want to come to a complete stop first. In that case double clutching to speed up the transmission made a smooth downshift possible.

[benb]

Yep.. I do it to downshift to first while moving.. rarely though.

[Craig Ryan]

Knowing the principles behind it, and being able to drive any vehicle w/o the clutch is a good skill to acquire. If you ever break a clutch cable, which 80's era VW's were notorious for, you can get where you need to go. Getting the car rolling is another issue.

[davidlee]

Knowing the principles behind it, and being able to drive any vehicle w/o the clutch is a good skill to acquire. If you ever break a clutch cable, which 80's era VW's were notorious for, you can get where you need to go. Getting the car rolling is another issue.

LOL.. Been there done that: Turn ignition off, put car in first, make sure no one is in front of you , turn ignition on and get ready to shake and GO!!!