Gearing in 1980s 4-cylinder cars

[Number_35]

Our '90 Mazda MPV with the 2.6 litre inline 4 and 5-speed MT ran at 2500 RPM at 100 KPH (62 MPH). It seemed happy there, and turned in good mileage.

The '09 Mazda5 with 2.3 l/5MT runs at about 2700 RPM @ 100 KPH, and again seems happy and is easy on fuel.

Can't remember the particulars for the '85 626, and my earlier cars didn't have a tach.

Toyota claimed, quite a few years ago, that an engine ran most efficiently at about 50% of redline, and geared its cars accordingly during the 55 MPH federal speed limit.

 

[cb_13]

My 02 Escort ZX2 had a 4.10 final drive ratio. That’s why it’s fuel economy on the interstate wasn’t the greatest. Still the most reliable long term vehicle I’ve had. Although of all things our 17 Explorer(not the most reputable platform)was on par, just not kept as long.

 

[Chris142]

My first car a 1978 Toyota long bed pickup had the optional 4.35 gears. Iirc my 86 d50 had 3.90.

 

[Hermann]

The 2000 Focus with 5 speed manual turned about 3200 rpm at 70 mph

 

[addyguy]

Family had an ‘89 Tercel 4-speed, at 60+ mph it sounded like it would explode. No tach, but easily 3500-plus rpm.
Our recent Kia Soul 4-speed auto also turned 3000 rpm at 60 mph; it droned badly at highway speed. It is the main reason I sold it and kept my G5 when my wife got her Jeep - G5 is at 2100 rpm at 60 mph, and very quiet, and all I do is my highway work commute now.

 

[Oillover]

4th gear on a 4 speed is usually 1:1...and on a 5 speed is still 1:1, 5th gear is overdrive.

No, the point of "overdrive" gears is a ratio lower than 1:1.

 

[Oillover]

I had a 95 geo prism no tachometer with the 3 speed automatic. At 65 the motor was screaming felt like it was going to jump out on my lap. Great around town beater horrible highway cruising

Lol, you think that's bad?
My older brother had a first gen Honda Civic with the "Hondamatic" (I'm sure a few reading this will recall seeing the rear emblem on the cars).
Anyway, those autos were only 2 speed. He thought there was something wrong with it when it failed to shift into 3rd, but that's all the gears it had!

 

[dishdude]

Lol, you think that's bad?
My older brother had a first gen Honda Civic with the "Hondamatic" (I'm sure a few reading this will recall seeing the rear emblem on the cars).
Anyway, those autos were only 2 speed. He thought there was something wrong with it when it failed to shift into 3rd, but that's all the gears it had!

I thought you had to manually shift those, it was like clutchless manual. I remember seeing a graph on the speedo that showed what speed to shift to second

I think they also had some weird cable attached to a lever in the center console that would lock and unlock the rear doors.

 

[barryh]

According to the data I can find (car has no tach to confirm), this has a 4.10 final drive ratio with a .81 4th gear ratio. With 24" tall tires, the calculators say that at 85MPH, the engine will be turning almost 4000RPM in 4th gear (top gear). (I thought it was interesting that I could shift into 4th at 25MPH without any complaint from the engine, but this short gearing explains why!)

Is this common for 1980s 4-cylinder vehicles? Given that, when they were designed,

At a little over 20mph per 1000rpm this gearing is unreasonably short by modern standards, but it was not uncommon back in the 80's. I had a 1989 2.0 litre Mercedes with similar gearing and I didn't like it. The equivalent car today is geared at 30mph/1000rpm

I call it the German approach. German cars were geared so that at their maximum speed the engine revs were already above peak power revs. The logic of this approach was that when encountering a hill at maximum speed on the autobahn, the engine revs would fall back towards peak power and aid the car in maintaining speed up the hill. That's now a dated philosophy which has been replaced by concerns about MPG and emissions.

 

[Motu]

No, the point of "overdrive" gears is a ratio lower than 1:1.

That's what I said - 4th is direct, 5th overdrive. On a rwd gearbox 4th is just straight through the mainshaft, no gearing reduction at all. 5th is overhung off the rear, and overdrive. I've never seen a direct drive 5th, it's always overdrive.

 

[eljefino]

My 1982 caddilac cimarron had the 5500 RPM yellow line, 6k RPM redline on its tach, on its 1.8 liter engine. This was enlarged to the 2.0 you find in your Cavalier. It was not improperly geared with the TH125C 3 speed with lockup trans, as the 85 hp engine in a 2800 lb body had its work cut out for it.

My grandma's 93 Corolla with 3 speed auto was very buzzy at highway speeds. It found third at 22 mph sometimes. My 02 Prizm had VVti and, with the same trans, didn't seem awful at 70. They may have tuned the exhaust to be less buzzy, IDK, but it was a solid if cheap setup. And one of the last 3-speed autos sold in America!

My 1989 Mazda 323 turned 3500-4000 RPM at 65 MPH in 5th gear. Incredibly, 5th gear was optional for that car; the stripper model went to 4th and kept the same ratios! Consumer Reports said it was "buzzy". No kidding!

Dad's 93 Ford Escort had higher gearing and was low-strung with its 1.9 L engine. Tuned for torque, it ran out of breath when passing. My 95 Saturn SOHC was similarly geared.

We all "know" turning lower RPMs and lugging the engine keeps pumping losses down but I bet the Japanese had good reasons for spinning the RPMs.

 

[Jetronic]

88HP @ 4800RPM, 110 lb-ft @ 2400RPM

very low top speed then, probably approriately geared. 88 Bhp only goes so far. My first car had even less (60 bhp) but it only weighed 1500 pounds and had a small cross section.

 

[wheelman1991]

My 85 Mercedes 190d is the same way, it has a silly 4 speed auto where 4th is 1:1 (no overdrive) and unless you pull the shifter All the way down, it takes off in 2nd. I have no idea what they were thinking creating essentially an automatic version of the three speed with a granny low. At 60mph, The little diesel is turning 3100 RPM with a 24.5 inch rear tire. (no load "redline" is 5000)

 

[IndyIan]

The 2000 Focus with 5 speed manual turned about 3200 rpm at 70 mph

My 06 runs about 2500rpm at 60mph, so 2900 at 70mph with the mtx75 and 2.0 duratec. I have 195/65/15 on it instead of 195/60R15 and now the speedo is right on.
My 95 3spd auto Neon ran about 2900rpm at 60mph and I did most of my passes in 3rd, no need to force a shift to second. I test drove a 2003 Neon RT with the 5 spd and 5th was about the same ratio at 3rd in my 3spd auto...

 

[zzyzzx]

There is a 1984 Cavalier still on the road???

 

[wander2039]

The Festiva runs between 3-3500 rpm at any speed above 65. The 55 speed limit changed around 95 I think so yeah these cars are more geared toward the lower speed. I got my license in 96 and dad would always yell at me when I'd try to go the new speed limit lol. The Festiva will still get above 40mpg though. All my other slightly modern vehicles run 2-2500 at the same speeds, even the Focus.

 

[Kurtatron]

My 1982 caddilac cimarron had the 5500 RPM yellow line, 6k RPM redline on its tach, on its 1.8 liter engine. This was enlarged to the 2.0 you find in your Cavalier. It was not improperly geared with the TH125C 3 speed with lockup trans, as the 85 hp engine in a 2800 lb body had its work cut out for it.

My grandma's 93 Corolla with 3 speed auto was very buzzy at highway speeds. It found third at 22 mph sometimes. My 02 Prizm had VVti and, with the same trans, didn't seem awful at 70. They may have tuned the exhaust to be less buzzy, IDK, but it was a solid if cheap setup. And one of the last 3-speed autos sold in America!

My 1989 Mazda 323 turned 3500-4000 RPM at 65 MPH in 5th gear. Incredibly, 5th gear was optional for that car; the stripper model went to 4th and kept the same ratios! Consumer Reports said it was "buzzy". No kidding!

Dad's 93 Ford Escort had higher gearing and was low-strung with its 1.9 L engine. Tuned for torque, it ran out of breath when passing. My 95 Saturn SOHC was similarly geared.

We all "know" turning lower RPMs and lugging the engine keeps pumping losses down but I bet the Japanese had good reasons for spinning the RPMs.

Was your 323 the one with 600k miles? Someone on this forum had one.

 

[wheelman1991]

My 85 Mercedes 190d is the same way, it has a silly 4 speed auto where 4th is 1:1 (no overdrive) and unless you pull the shifter All the way down, it takes off in 2nd. I have no idea what they were thinking creating essentially an automatic version of the three speed with a granny low. At 60mph, The little diesel is turning 3100 RPM with a 24.5 inch rear tire. (no load "redline" is 5000)

* Engine is turning 2900@ 60 mph. I accidentally used data from when I had 185/65/14 on the rear, not the current 185/65/15

 

[hrv]

I remember my 1973 Dodge Colt GT with a 1600 CC engine and a three speed auto..At 70 MPH or so the tach was around 3300 rpm...

 

[barryh]

My 85 Mercedes 190d is the same way, it has a silly 4 speed auto where 4th is 1:1 (no overdrive) and unless you pull the shifter All the way down, it takes off in 2nd. I have no idea what they were thinking creating essentially an automatic version of the three speed with a granny low. At 60mph, The little diesel is turning 3100 RPM with a 24.5 inch rear tire. (no load "redline" is 5000)

It's another German or specifically a Mercedes thing. I had the same 4 speed auto in a 190e which was for all intents and purposes a 3 speed. It was a poor auto compared to other contemporary 4 speed autos. I don't know why exactly they have 1st so low as be useless but the trait continues to this day. I have a 2009 6 speed manual and 1st is only good for hill starts. Even the handbook advises that you should set off in 2nd on the flat. Autos are still the same in having a very low 1st gear. They may have resolved the top gear issue by having 9 speeds but they still start off in 2nd meaning they are really only an 8 speed.