Manual transmission - help solve a dispute!

Factual Questions
1

My SO has a tendency to shift a 5-speed car at very low rpm’s. As in being in 5th gear at 25-30 mph in a Ford Escort - and then accelerating, so the car “chugs” enough that I can feel it from the passenger seat. I maintain this is just not very good for the car; he says that because he shifts when the “shift” light comes on, it’s OK. (Personally I think that if one has to rely on those dummy lights, one should stick to automatics.) it’s his car, so I shouldn’t really care, except it does set my teeth on edge! Anyhow, we had a discussion about this & I thought I would throw the question to the teeming millions.

He just had to replace the 100K timing belt at 51K, and is on his second clutch on his pickup with 105K miles, though whether this is driving habits or FoMoCo engineering, I don’t know.

? :slight_smile:

2

thanks for posting this:
I drive a stick, as does my ex. we have a 16 year old son, who is learning to drive on both, from both. Bad news.

My car doesn’t have the light described. I’ve seen the phenonmenon you’ve described - I tend to shift rather in the middle of the cycle - neither when it’s slugging like you talk about, but also not when it’s whinning really high (this is when my son tends to shift, as taught by his father).

I’m looking forward to the discussion.

3

5th gear at 25?!? I’ve got an Escort and it doesn’t tell me to switch to 4th around that time and I normally don’t! they’d don’t call em “Idiot Lights” for nothing you know. :slight_smile: I think that’s way too low to be shifting. Plus I think the 5th is Over drive anyway and there’s NO power in OD. Actually you would be wasting more gas in 5th at 30mph than in 3rd. Oh and my idiot light comes on and then goes off, it is more of a suggestiong if you want to keep going at that that speed. let me think of when I change gears

2nd around 5-10 mph
3rd around 20
4 around 35-40
5 around 50

4

Well, I’m no expert, but I can say that I try to avoid shifting too early because I want to avoid the jerking phenomenon you describe, and my little engine can’t accelerate the car very well if i’m in a high gear. For what it’s worth, I have driven 164,000 miles on my current clutch, and it’s similar in size/power to your SO’s (1995 Mazda Protege). I replaced the timing belt at about 90K miles, but I don’t know if the timing belt has much to do with the lurching you describe.

P.S. my brother’s Saturn has one of those shift-up lights and it annoys the hell out of me. Your SO should cover it with masking tape! Remember the sensor that controls that light has no idea whether there’s a steep hill right in front of you, or if the speed limit just went from 55 to 30 (or from 30 to 55).

5

I used to calibrate auto transmissions when I worked for one of the Big 3. In automatic transmissions, shift points are determined by throttle position and vehicle speed. It’s dependent of both…It takes a lot of trial and error to get the vehicle shift speeds to a desirable, comfortable, and fuel efficient set-up.

If you shift a vehicle at low throttle you need the vehicle to gain more speed before going to higher gears. It takes longer for the engine to produce the torque necessitating a shift. If you are down hard on the throttle you must shift earlier to avoid over revving the engine at lower speeds. There’s an entire matrix of shift points involving these two variables. Each matrix depends on the vehicle, the engine, and the transmission designs.

It’s a judgement call in a manual transmission. But clutches wear quicker when they you “ride” them longer. This is more likely to occur when you shift too early, rather than too late.

6

wring wrote:
…I tend to shift rather in the middle of the cycle - neither when it’s slugging like you talk about…

The term is “lugging,” not “slugging.”

That is all.

7

Hurting anything? No. Someone will come in and tell you that it causes excessive vibration and that could hurt engine mounts…blah blah blah.

Quit the whining everyone. The shift light usually comes on at such a low rpm that a very very light application of the accelerator is required as to create almost nil “load” on the engine or risk it shuddering. The shift light is a, repeat after me, “guideline”. With a passenger or a slight incline, or a damp day, or any numerous factors, the ideal shift point might go up a bit. An engine in ideal tune, with no incline and all factors in it’s favor can be shifted consistently at the lighting of the shift indicator (and this is a big MAYBE).

Tell your SO to lose the wimpiness and kicked up the RPMs a touch. No precious fuel will be wasted, everything will run smoother and the world will be a better place.

Here’s some ammo: Does a vibrating engine and tranny say “I’m a happy little car” or does it say “Hey, knucklehead, I’m dying down here. How about a couple more RPM to make things smoother?”

Let me go bang my head against the wall because someone will defend the assinine engine shift light as if it’s the all knowing, all mighty OZ of idiot lights.

8

Hurt something? Possibly. If you shift and the engine is “lugging” enough, detonation may occur (Sometimes sounds like a “ping”). That can be very bad if it happens often and for long enough. It is possible that if the detonation is bad enough, it actually may put a hole in the top of the piston.

As a safe rule of thumb, shift so that the gear you are going into puts the engine at around 2000RPM. At least thats what I do :slight_smile:

9

If you can actually feel the car bucking, then the clutch is alternately sticking and slipping. This will cause premature wear on the pads and a premature big repair bill for the clutch rebuild.

Short of that, upshifting at the lowest RPM that will not cause such bucking will maximize fuel efficiency, but at the expense of acceleration and fun.

10

Thanks so far!

I HATE those idiot lights. I had a POS Blazer once with one, and I put electrical tape over it on the first day I owned it, when the dealer refused to disable it.

I probably shift like Edward, depending on the car & the road. I used to have a Porsche 944T, and on windy fun roads would often still be in 3rd at 60 or 70 mph because it felt like I had much more control when it was wound up a bit.

I’m not an expert, nor particularly mechanically inclined. But I spent several years driving over the road in a semi, and have owned a couple of fairly high performance cars and like to think I’m a way above average driver (ok, so don’t we all!) Anyway I’ve driven hundreds of thousands of miles, on several continents, accident free. Just a few…ummm…speeding tickets. oops. So I’m not a very good passenger, basically!

11

5th gear at 25??!!! That’s no way to drive a manual!
At 25 mph you shift from 1st to 2nd.
At 50, put it in 3rd.
At 70, go for 4th gear.
5th gear is for three-digit speeds :slight_smile:

12

When I moved from Minnesota to England several years ago, I had to take a driving test. I was marked down points because when the car was going 30 mph, I was only in 3rd gear. According to the instructor, “the car was screaming to be in 4th.” (I said: "no, you must be reliving the bomb raid sirens…ba dum!).

Whatever, in 4th gear in that Ford focus I could have gone from 30 to 60mph in about 137 seconds. Talk about no response!

As an interesting side note: they ask questions about road signs and stuff when you are done driving. They have flash cards and so forth, you identify what they mean. They also ask other questions. One of mine was: what is the minimum acceptable depth of a tire tread? the answer: 2mm!

Yes, now I check my tires every time before I drive…

13

That sounds about right, and you do have much better control when the engine is in it power band.

As far as shifting at lower RPMS all the time, that can possibly cause a carbon buildup over time, increasing compression, and making detonation more likely. Since detonation can cause engine damage, it is my belief that, indirectly, shifting at a low engine speed all the time can cause engine damage eventually.

I don’t even notice the shift light in my truck anymore. In fact when I do notice it, I wait 'til it goes out to shift just to spite the automotive engineers that think they should tell me how to drive.

14

“5th gear at 25??!!! That’s no way to drive a manual!
At 25 mph you shift from 1st to 2nd.
At 50, put it in 3rd.
At 70, go for 4th gear.
5th gear is for three-digit speeds”
Really people, why don’t you look at the manual that comes with the car? That’s why they make manuals, the book type you know?

15

I have never driven a car with a shift light. I usually just go by the tachometer… in the Trooper I tried to keep it between 2000 and 3000, now in the MR2 I try to keep it between 3200 and 4200.

I think I typically shift to 2nd at 25, 3rd at 40, 4th at 55, and 5th whenever I reach a constant speed on the freeway and I have a free hand to keep it from popping out of gear. I avoid lugging not because I know it’s bad for the car (although ElvisL1ves’s explanation makes sense), but because it makes me feel like an idiot and I can’t accelerate like I want to.

When I drove a 4-speed diesel Vanagon with no tachometer, I wouldn’t shift until it wouldn’t go any faster in the gear I was in (I’m guessing 2nd at 10, 3rd at 25, 4th at 45). I don’t know if that was a good idea, but it sure kept running.

16

You have more control when your car is near its optimum of the torque curve. This means higher revs than the “optimal shift points” indicated by the idiot lights.
A 944 Turbo might have an optimum torque output at 6,000 RPM even. Porsches aren’t exactly shy when it comes to reving.

This also explains the following. Take two FWD cars, identical. One is automatic, and one is a manual. Now, try to take a 90[sup]o[/sup] corner at a considerable speed (say, 30 MPH - yes, most cars can easily handle that). With the manual, you take it in second, probably reving somewhere in the 4,000 range. The auto will, upon release of the throttle, select top gear and almost idle.
Result: the manual has torque at the throttle immediately, and will stick to the road. The auto, however, will lack torque, and start sliding over the front wheels (understeer) much sooner. I’m for the sake of the argument forgetting about extremely intelligent automatics, such as those in the BMW 7-series. They will, when you select the right program, downshift automatically. A Nissan Sentra or similar won’t, however.

“Idiot lights” are pretty rare in European cars. My car has a rev-meter (which isn’t even a standard on most budget models), but I rarely look at it. A decent driver just “feels” when to shift up, IMHO. I only check the revs when I REALLY make it scream, for the heck of it (and it’s actually GOOD for a car to occasionally step on it).

Another thing that wasn’t mentioned yet, but is very important in this discussion.
When a car is not near its torque potential, it is wasting fuel.
Most people think this just just applies to high revs. Wrong - accelerating from 40 MPH in fifth EATS fuel as well. As said, the car produces the most torque (read: “ease to produce power to the wheels”) at considerably higher revs. You don’t have to floor it, but at least make sure it hits 3,500 or 4,000 RPM during acceleration. A lugging engine is a costly engine.

17

When I got out of college and got my first job (this was in August 2000 - very recently) the first thing I bought was my car - 2000 Mustang GT Convertible. I bought an manual because it’d seem like a waste to have a automatic, but there was one problem - I COULDN’T DRIVE STICK!

My only other driving experience was my mom’s Chevy Corsica. So I took my lumps - I stalled four times getting the car out of the dealers’ lot, in the meanwhile getting jeered at by all of the employees, except for the salesmen who knew better. I’m suprised I didn’t get pulled over because I must’ve looked like a young punk on a joy ride in a stolen vehicle.

After a week or so (and who knows how much damage to the car, thank goodness for warranty heh heh) I finally got the hang of not stalling out every time I have to go from a start at a light. I read the owners manual thouroughly to perhaps glean some points on how to drive this thing (i.e. when to shift). It’s recommendations were:

Shift to 2nd at 15 mph
Shift to 3rd at 25 mph
Shift to 4th at 35 mph
Shift to 5th at 45 mph

So I did, and only “pushed” the car (sometimes going as high at 4000 rpm!!!) when I was feeling cocky. Doing as the owners manual said, I ended up shifting at around 2,000 rpm. Why would the owner’s manual tell me to drive the wrong way? I didn’t understand what Max Torque at 4000 rpm meant or Max Horsepower at 5250 rpm meant, so I ignored it, but I was getting an average of 19.5 mpg combined, which was amazing since I assumed I’d get more like 15 mpg.

Then I played Gran Turismo again and noticed that the car on there shifted on redline when in automatic, and rarely did it ever fall under 4,000 rpm or so. So I thought, hmm, maybe I should try that…

Well, I did, and WOW it was like having a new car! Sure, my gas mileage hovers around 15 mpg now, but it’s SO worth it! I spend $900 a month on that friggin’ car (to put in perspective, I pay $385 a month on rent) so I think I should enjoy it!

Well, now it purrs, growls, and genuinely drives like I always thought it should. And I’m never going to read an owner’s manual again.

18

I’ve been driving Camaros for a number of years now and currently have a 2000 SS w/6-speed manual transmission. It likes to shift at about 2000 RPMs but will do 50 MPH in first gear at 5000 (it redlines at 7000). It takes longer to get up to speed if you shift lower than that.

I had a '92 Camaro that had one of those damn dumb shift lights. The owner’s manual said that if you shifted when the light came on it would save fuel. I say if your major concern is saving fuel, you have no business driving a Camaro.

19

I have a headache. I never knew so many people didn’t know squat about shifting.

wbricks: enjoy the 'stang! Shift lower to go slower and save gas. Higher revs are for more spirited driving - of course! Let 'er rip once in a while.

:slight_smile: Dominique: I love your attitude! :slight_smile:
Shift when it feels right. Books, shift points and lights are suggestions and are usually for economy. I hope you all relaeze that for maximum accelaration you shift up near the redline (with some variances depending on the exact power band and gearing of your car).
Now, let’s discuss starting from a stop in 2nd gear!

20

There’s nothing wrong with starting a vehicle in 2nd gear. I do it all the time at work in the GMC Top Kick. Even in my own cars (mostly sporty types over the years), I’ll occasionally do it. Of course, If you’re facing a big hill 1st is probably a better choice. Now, on snow & ice, 2nd gear start is a much better idea. The reduced torque provided in the higher gear reduces the chances of inadvertent wheelspin. My dad’s 1997 LX450 has a button on the console to kick the auto tranny into 2nd gear start mode. A deep stab of throttle will kick it back down into 1st, but normal driving on snow and ice is much easier.