Extra gears: Not always better for FE
 

I knew that it's common practice to add more gears to a car's transmission and not increase its gear range, instead just making the ratios closer...but I had no idea that a 1992 Toyota Tercel would get worse FE with the optional 5 speed manual than it does with the 4 speed manual.

According to fueleconomy.gov:
1992 Toyota Tercel 4 speed manual: 27/30/33
1992 Toyota Tercel 5 speed manual: 25/28/33

The 4-speed has much taller gearing than the 5-speed. Honda did the same thing with the 88-91 Civics, if I am not mistaken. I test drove a 1990 Civic hatch with a 4-speed, and the 4th gear was taller than the 5th in another 1990 I drove.

GM is the king of tall gearing with fewer ratios (in their automatics). For example, a Buick Terraza reaches 89 mph in 2nd gear (4-speed auto). Wow.

That's what I figured. Why would they do that?

GM is definitely the king of tall gears and wide ratios in automatics...I'm always amazed at how fast the engine in anything else goes at highway speeds. I found it amazing that my VW cruises along at 3000rpm and I was even more amazed when I found out that it's quite common. I was raised mostly on GM and Ford and my own vehicles have mostly been large GMs and when I drive anything else I keep wondering if I'm in high gear.

that is weird... i noticed a similar trend in subarus. not between the auto and the manual but between the manual 5spd and 6spd. the top gear on the 6th (top speed ~=150) is substantially shorter than the top gear on the 5th (top speed ~=160).

i think gms tall gears are the secret to their success with any kind of efficiency. i mean how else are you going to get a 400+hp sports car to get 30mpg on the highway? slow down that motor.

Are more gears associated with sportier driving? I have the vague impression they are, but where I got that from I have no idea, not being a performance enthusiast of any stripe.

Wait a minute, the 4's 4th being taller than the 5's 5th doesn't make sense for those EPA ratings. By those EPA ratings, the top gears in both trannies are the same, but the 4 speed manual gets better city mileage.

More gears are associated with sportier driving. Sports cars got 6 speed transmissions before other cars (and you still can't find 6 speed transmissions in lots of non-sports cars). Standard practice seems to be that when they add a gear, they don't add a taller overdrive for the new gear; they just make closer ratios and/or a shorter 1st and 2nd. Closer ratios allows the car to stay in a narrower powerband while accelerating.

Eventually, additional gears will have to be for fuel economy. There's got to be a point where the extra time spent shifting is more than the time saved by staying closer to the optimum RPM.

Some new 6 speed automatics already don't use all their gears all the time. I don't remember which, but some manufacturer's automatics skip one gear on the way up which only gets used when downshifting, and it skips another when downshifting. The new Camaro SS doesn't use 1st except for when you first drive away while the engine is cold, and probably when you set the transmission in "Sport" mode. I don't know if the V6 Camaro does the same thing.

How do the final drive ratios compare? Transmission gearing is one of three major factors, final drive ratio and tire diameter are others.

I was thinking the same thing. maybe they put a different differential gear ratio in it (not sure what you call the front wheel drive version of this).

Lug_Nut, if you're talking about the Tercel, I have no idea what the gear ratios are OR what the final drive ratios are. I just know how many gears, and what the EPA ratings are.

I know my five speed 2008 VW runs the same RPM at 70mph in 5th as the six speed 2008 VW GTI in 6th.

It isn't the transmission that made the difference, it was the engine.

The 4-speed was paired with the base 1.5L 3E-E SOHC 3-valve, fuel injected 4 cylinder while the 5-speed was paired with the 1.5L 5E-FE DOHC 4-valve, fuel injected 4 cylinder.

Oh, that would do it. Fueleconomy.gov and a couple car specifications sites didn't mention two engines, but that makes more sense.

I'm trying to find an instance where the transmission gear ratios reduce for an increase in mileage but the only ones I can find either get worse mileage with the same engine or a different engine gets better. Like the Omni, 1.6l 4 speed gets 26/36 while the 2.2 5 speed gets 22/33

I found one!!! The 1985 2.2L Dodge Aries got 23/30 with the 4 speed and 22/30 with the 5 speed.

The Cali models don't do it but the 49 state version does.

First year ('84) Tempo/Topaz had a "Fuel Saver" 4-speed which featured a higher final drive ratio than the 5-speed. Can't put my finger on fe figures but I think the 4-speed was rated higher.

It is still called a diff ratio regardless of which end of the vehicle it is fitted to.

I agree with the comments about the larger engined cars (GM , Ford etc) using taller gears but it is worthwhile to remember the additional torque generated by the engines can easily manage to shift the vehicle even with the taller ratios.

I drove my brother's Subaru and kept wondering when it was going to change into "top" on the freeway.
It WAS is top but still turning a lot more revs than I was used to.

Cheers , Pete.

the really funny thing about that is that subarus are pretty long for 4 cylinders hahaha.

By 1995, both the 4-speed and 5-speed had the 93-hp, 16v engine. The 4-speed is rated 28/35 on the 2008+ ratings (31/36 on the sticker) while the 5-speed is rated 27/35 on the 2008+ ratings (30/34 on the sticker).

This is significant in that (1) the 4-speed is still rated higher, and (2) the 5-speed is actually rated HIGHER on the 2008 highway rating than on the 1995 rating.

I call it the "rear end gear" in a rear-drive car, and the "final drive ratio" in a front-drive car. I know they're all the same thing... I just grew up saying it that way.

What about 1992? The specifications site I found shows one engine for all models of 1992 Tercel.

1995 is a different generation. It's the 5th generation and has the 93HP OBD2 equipped 5E-FE.

In 1992(4th gen) they had the 82HP 3E-E and the 100HP 5E-FE. The 3E was discontinued in 94 and the 5E continued to like 98.

Yup. I just remembered an article on the Tercel from Car and Driver magazine from 1995. They drove the 4-speed. If I remember correctly, the Paseo had the same motor as the 1995 Tercel.

Ok, I had to look up the ratios and engine.
https://www.tercelreference.com/terce...cel_specs.html (ratios and engine)
https://www.tirerack.com (tire size - 155/80R13)
https://www.f-body.org/gears (gear calculator)

The Tercel site says there's only one engine available in the 1992 Tercel.

4 speed C141 transmission:
3.545, 1.904, 1.233, .885; final 3.526
MPH @ 2000 RPM - 11, 20, 31, 43
MPH @ 4000 RPM - 22, 40, 62, 87
RPM @ 25 MPH - 4700, 2500, 1600, 1150
RPM @ 50 MPH - explosion, 5000, 3200, 2300
RPM @ 70 MPH - explosion, explosion, 4500, 3233

5 speed C150 transmission:
3.545, 1.904, 1.310, .969, .815; final 3.722
MPH @ 2000 RPM - 10, 19, 28, 38, 45
MPH @ 4000 RPM - 21, 38, 56, 75, 89
RPM @ 25 MPH - 4850, 2600, 1800, 1350, 1100
RPM @ 50 MPH - explosion, 5200, 3600, 2650, 2250
RPM @ 70 MPH - explosion, explosion, 5050, 3750, 3150

So, the total range is about the same. The 5 speed has a marginally shorter 1st and a marginally taller 5th when you count the final gear. 1st and 2nd are almost the same; 3rd is a little shorter in the 5 speed; high gear is a little taller; and the 5 speed's 4th splits the difference.

I'm just not seeing a transmission-related reason for the city fuel economy rating to suffer. What else was included with the option package that had the 5 speed?




........crap, I just realized I left this message unposted, all ready to go an an abandoned tab in my browser. I referenced it in a post I've made since, too, thinking that I had already posted it.

Maybe the test protocol left the 5 sp in a lower gear than the 4 sp?

I'd actually like to pull a few gears out of my 5 sp. I skip shift all the time and a trans with 1-3-5 would be fine (I'm a flatlander though). I wonder how much trans efficiency gain there would be by having 4 less gears constantly meshing.

lol i wish my chevette had another gear... at 60 mph its at 3Krpm in 4th... it sounds like its about wound out, can deffinately tell when i stomp on the gas and it takes off fast when im goin at that speed...

there was an optional 5 speed, the more powerful diesel engines got that standard and was an option for the gas cars...

My truck has a 4 speed (87 S10 2.5l 4 cyl. zero options) and after my tweaking, got as high as 29.5 hwy mpg turning 1000 rpm for every 20 mph (before I changed axles and lost 6 mpg off the top (with the same gearing too. wtf)) next fall I plan on swapping it for an 5 speed off a truck at school. the 4th (and last) gear in it now is the same ratio as most 5-speeds 4th gear (1:1) we'll see how that goes. any reduction in highway rpms should help and tho it's only rated at 90 hp, power isn't a problem: it can top 80 mph carrying 1400lbs (almost half it's own weight).