Difference between a 5 speed and a 6 speed?

Nasir · Post by **Nasir** » Sun Dec 11, 2005 9:17 pm

Other than the obivous extra gear,whats the difference.What does the extra gear do?

Post by **Johnf514** » Sun Dec 11, 2005 9:28 pm

Fifth and 6th gear are overdrives, used for cruising and steady highway driving. All 6th does is give you more rotations of the wheel per engine RPM than 5th. A smaller engine cannot handle the amount of torque needed at such low RPMs. However, a larger V6 or V8 can usually keep up with the gear, as long as speeds are upwards of 60-70 MPH, depending.

VTECaddict · Post by **VTECaddict** » Sun Dec 11, 2005 9:46 pm

the ratios of the 5th on the 5speed car and 6th of a comparable 6speed car pretty close. the difference is that gears 1-5 are usually spaced closer....hence why most 6 speeds are called "close ratio" 6 speed transmissions

for example, i believe the 5 speed base RSX and 6 speed RSX-S have the same ratios for the last gears.

Post by **IMBoring25** » Sun Dec 11, 2005 11:18 pm

When you add a ratio, you can use it to provide a lower first gear for more responsive acceleration from a stop, to provide a higher top gear for better highway fuel economy, or to space the gears more tightly together to give the driver more choices to keep a peaky engine in its powerband.

Usually, where both 5 and 6 speeds are available, the extra speed is used to do a little of all three.

Sypher · Post by **Sypher** » Sun Dec 11, 2005 11:38 pm

If you're driving a 5 speed version of a car going at 100km/h at 3k rpm in 5th, would you be going at the same or lower rpms if you were driving the same car with a 6 speed going at the same speed?

for example, a RSX 5-speed and a RSX-S 6-speed

Post by **IMBoring25** » Mon Dec 12, 2005 2:42 am

The RSX is indeed one of the cars that has basically the same overdrive gear in both transmissions (And the same axle ratio and the same size tires, so, accordingly, basically the same engine RPM on the highway with both transmissions). It also has the same first gear. What the RSX changes is the spacing between the gears, which is demonstrated by the reduction in RPM accompanying an upshift from the previous gear:

Base RSX
1 : 3.266
2 : 1.880 (RPM falls by 42%)
3 : 1.212 (RPM falls by 45%)
4 : 0.921 (RPM falls by 24%)
5 : 0.738 (RPM falls by 20%)

RSX Type-S
1 : 3.266
2 : 2.130 (RPM falls by 35%)
3 : 1.517 (RPM falls by 29%)
4 : 1.147 (RPM falls by 24%)
5 : 0.921 (RPM falls by 20%)
6 : 0.738 (RPM falls by 20%)

As you can see, the ratios are closer together, especially where they practically put two gears (3 and 4) where only one (3) existed before.

Ironically, I got to drive a relative's RSX-S over the Thanksgiving holiday. In daily driving, I see no need for all those gears. The 1-2 shift seemed pretty normal, but the rest of the box felt like the gears were right on top of each other. I wound up using 1-2-4-6 in town, and would have been quite capable of getting myself in trouble on any public road using that sequence. On the track, however, the car would need all those gears to make use of its peakier powerplant (The base RSX has 2500 RPM between the power and torque peaks...The RSX-S has only 1400 RPM between them), selecting the appropriate gear to wring the most out of the car on every part of the track.

Some other like vehicles available in both configurations include:

2006 Mazda Miata's extra gear goes almost exclusively into a more-aggressive first gear. (Most sources say both versions now have the same axle ratio, which they did not before; I reserve the right to revise and extend my remarks).

2006 Mazda MX-5:
3.14
1.89 (40% RPM Drop)
1.33 (30% RPM Drop)
1.00 (25% RPM Drop)
0.81 (19% RPM Drop)

2006 Mazda MX-5 6-speed:
3.82 (22% more-aggressive first gear)
2.26 (41% RPM Drop)
1.64 (27% RPM Drop)
1.18 (28% RPM Drop)
1.00 (15% RPM Drop)
0.83 (17% RPM Drop, 2.5% higher cruise RPM)

When the gas Super Duties got the six-speed, it went mostly to lower cruise RPM's and tighter gear spacing.

Early-model Ford Super Duty:
5.72
2.94 (49% RPM Drop)
1.64 (44% RPM Drop)
1.00 (39% RPM Drop)
0.76 (24% RPM Drop)

Late-model Ford Super Duty:
5.79 (1% more-aggressive first)
3.30 (43% RPM Drop)
2.10 (37% RPM Drop)
1.30 (38% RPM Drop)
1.00 (23% RPM Drop)
0.72 (28% RPM Drop, 5% lower cruise RPM)

Sypher · Post by **Sypher** » Mon Dec 12, 2005 1:41 pm

wow nice research there IMboring

.

Can you explian how to read the gear ratio's plz?

I have an idea of how to, but I just want to know how it's properly done

Post by **IMBoring25** » Mon Dec 12, 2005 2:21 pm

The gear ratio is the number of times the input shaft spins for every time the output shaft spins when the transmission is in the given gear.

With the clutch out, the engine is firmly attached to the input shaft, so it could also be considered the number of times the engine turns for every time the output shaft spins.

Then, there's typically one more gear reduction in the differential, so that the number of times the tires spin (Not taking into account the low-range transfer case on 4WD vehicles) for every time the engine spins is equal to:

(Gear Ratio) X (Axle Ratio).

For a six-speed Super Duty with the 4.30 axle in first, the engine spins 24.9 times per rotation of the tires. In sixth, it's 3.1 times. Take into account the overall size of the tires, and you can then get a reasonably good approximation of a correlation to vehicle speed.

Nasir · Post by **Nasir** » Sat Dec 31, 2005 7:13 pm

How about somebody puts it lamen(sp?) terms

Sypher · Post by **Sypher** » Sun Jan 01, 2006 12:19 am

i would have thought someone going to ivy league would understand that

j/k don't want to start that again now do we

So, think of the input shaft as the engine. The output shaft as teh driveshaft going into the drifferntials located in the centre of the axle.

Like IMBoring said, Gear ratio x axle ratio = number of time the engine spins per turn of the wheel.

In his example, he used a ford superduty which has a first gear ratio of 5.79 and an axle ratio of 4.30.

5.79 x 4.30 = 24.9

therefore, for every spin of teh wheel, the engine needs to spin 24.9 times.

thats my take on what he said. Correct me if I'm wrong.

Post by **IMBoring25** » Sun Jan 01, 2006 12:46 am

I'm not sure how to get it too much more laymen's terms than that, but I can relate it to a multi-speed bike, if that might help at all.

If I have a hypothetical three-speed bike with overall gear ratios of 20:1, 8:1, and 2:1, then when it's in first, the pedals will turn twenty times for every turn of the wheel. When it's in second, the pedals will turn eight times for every turn of the wheel. When it's in third, the pedals will turn two times for every turn of the wheel. Lower gears give better leverage, acceleration, and pulling power, where higher gears give better mileage.

The car has a similar set of gear reductions (And usually one direct, 1:1 drive plus one or two overdrives) inside the transmission, and one further gear reduction at the differential that the power goes through regardless of which gear you're in.

If the engine turns two times for every turn of the output shaft and the output shaft turns three times for every turn of the tires (Pretty close to the configuration for many cars' second gears), using one turn of the tires, you get three turns of the output shaft, and since the engine turns twice for every turn of the output shaft, you get six engine turns, for a 6:1 overall gear ratio given a 2:1 second gear and a 3:1 differential ratio.

Sypher · Post by **Sypher** » Tue Jan 03, 2006 1:19 pm

After learning about gear ratios, there has always been something puzzling me. What exactly is the final gear ratio? I know that if you set it, it affects all teh gears but what exactly is it?

scionkid · Post by **scionkid** » Tue Jan 03, 2006 2:04 pm

I think you're refering the to axle ratio. The output of the transmission spins another reduction gear before the rotation makes it to the wheel. To get the overall ratio of a particular, you multiply the transmission's ratio of that gear by the axle ratio.

The final ratio gives you a greater range without making an oversize transmission. For instance, 1st gear overall ratio is typically 15:1. If you have this reduction done in the transmission, you'll need a really big gear (7.5 cm dia. drive gear and a 77.5 cm dia. driven gear). Now, with a axle reduction gear, your first gear can be a 4:1 reduction gear. Then you pick a ratio in the axle the reduces the overall ratio to 15:1.

Sypher · Post by **Sypher** » Tue Jan 03, 2006 5:08 pm

not quite understanding what you are trying to say but are you refering to the final gear as the axle ratio?

here's an example with different honda transmissions
http://forums.hondashowoff.com/index.php?showtopic=4048

does the "final drive" mean the axle ratio?

scionkid · Post by **scionkid** » Tue Jan 03, 2006 5:31 pm

In their context, final drive = axle ratio.

Like I said, the axle ratio is a reduction gear from the transmission's output shaft to the road wheel.

To find the overall gear ratio, you multiply the transmission's gear by the axle ratio to get the overall speed reduction from the engine to the road wheel.