5 and 6 speed automatic transmisions?

[Boomyal]

Is it only the final gear, in either of these transmissions, that are overdriven?

 

[bruceb58]

Re: 5 and 6 speed automatic transmisions?

What vehicle?

Not sure it really matters since you have to take the final drive ratio into consideration since the diff has its own ratio.

 

[Boomyal]

Re: 5 and 6 speed automatic transmisions?

What vehicle?

Not sure it really matters since you have to take the final drive ratio into consideration since the diff has its own ratio.

Ford Transmissions, in particular. Some Explorers have 5 speeds. My wife's 2005 Lincoln LS is a 5 speed, as well. Apparently a lot of newer cars have gone to 6 speeds.

 

[Cheetah 210es]

Re: 5 and 6 speed automatic transmisions?

Typically its a 1/2 gear ratio in top.

 

[bruceb58]

Re: 5 and 6 speed automatic transmisions?

For smoother shifts and possibly fuel economy.

 

[tpenfield]

Re: 5 and 6 speed automatic transmisions?

My car has 7 speeds . . . Supposedly to keep the car in its optimum power/efficiency range as you accelerate. I believe that only the last gear is an overdrive ratio.

 

[Cheetah 210es]

Re: 5 and 6 speed automatic transmisions?

Auto or manual, Regardless of number of gears top gear is roughly direct drive, the transmission input and output shafts are running the same speed, 1:1. With overdrive the output shaft will turn a little faster, maybe 1:1.2
Bruce is correct also, the more gears you have the closer the ratio's are together so the engine can stay in its power/economy band. The old granny transmissions had a huge gap between 1st and 2nd because the ratios were so widely spaced.

 

[raven7]

Re: 5 and 6 speed automatic transmisions?

Ford's new six speed Select Shift transmission. This would be a double overdrive.
6R140 Gear Ratios:
First - 3.97:1
Second - 2.32:1
Third - 1.52:1
Fourth - 1.15:1
Fifth - 0.86:1
Sixth - 0.67:1

 

[Boomyal]

Re: 5 and 6 speed automatic transmisions?

Ford's new six speed Select Shift transmission. This would be a double overdrive.
6R140 Gear Ratios:
First - 3.97:1
Second - 2.32:1
Third - 1.52:1
Fourth - 1.15:1
Fifth - 0.86:1
Sixth - 0.67:1

Wow!

 

[Boomyal]

Re: 5 and 6 speed automatic transmisions?

Ford's new six speed Select Shift transmission. This would be a double overdrive.
6R140 Gear Ratios:
First - 3.97:1
Second - 2.32:1
Third - 1.52:1
Fourth - 1.15:1
Fifth - 0.86:1
Sixth - 0.67:1

Wow!

 

[Splat]

Re: 5 and 6 speed automatic transmisions?

my dodge ram has a 5 speed auto in it, gears 4 and 5 are both overdrive.

Bill

 

[levittownnick]

Re: 5 and 6 speed automatic transmisions?

I have an 2011 GMC Arcadia that I am told has a 6 speed transmission. When driving above about 50 mph, sometimes there is a hesitation when accelerating. The dealer says that it is "normal" because of the 6 speed transmission downshifting. Twice it appeared that the transmission just shifted into neutral with the engine rpm jumping to over 6K and no acceleration of the vehicle.

Needless to say that I'm not happy with that.

 

[robert graham]

Re: 5 and 6 speed automatic transmisions?

Mercedes Benz has an 8 speed, but you wouldn't think their torque curve was so narrow that it would require 8 speeds...and if/when that transmission dies, think of repair costs$$$$ Very tall 6th and 7th speeds can't be worth much if your engine won't pull it?...guess it just keeps shifting back down on hills. Must be all about those Government fuel economy ratings!

 

[RogersJetboat454]

Re: 5 and 6 speed automatic transmisions?

Mercedes Benz has an 8 speed, but you wouldn't think their torque curve was so narrow that it would require 8 speeds...and if/when that transmission dies, think of repair costs$$$$ Very tall 6th and 7th speeds can't be worth much if your engine won't pull it?...guess it just keeps shifting back down on hills. Must be all about those Government fuel economy ratings!

It's not to make up for a narrow torque curve. It's more for a smoother transition between shifts. Extra gears above what is considered the typical amount, doesn't necessarily mean the car has a bunch of overdrives. It usually means that the gear ratios are much closer together. The typical MB driver likes a vehicle to feel as though they are gliding along on a big puffy cloud (no noticeable gear changes). Multiple gears with close ratios will accomplish this. I would venture a guess that if a MB owner that has a vehicle equipped with an 8 speed were to happen to have the opportunity to drive an old Chevy with a 6 cylinder, and a Power Glide 2 speed automatic, they would probably think the car is broken.

Oh.. and I'm not to worried about the what the person who can afford to buy such a vehicle in the first place has to pay when it breaks...

 

[robert graham]

Re: 5 and 6 speed automatic transmisions?

My mom's 1949 Buick had a Dynaflo Transmission with no gears at all...just smooth fluid drive...probably not very efficient?

 

[RogersJetboat454]

Re: 5 and 6 speed automatic transmisions?

My mom's 1949 Buick had a Dynaflo Transmission with no gears at all...just smooth fluid drive...probably not very efficient?

Nope, not at all...
They were built with multiple stages in the torque converter (extra turbines and stators), which made them nice and smooth and very inefficient.

 

[rogerwa]

Re: 5 and 6 speed automatic transmisions?

My Mazda 6 has a 6 speed manual (with a 2.5l I4). When crusing at 70mph I am running about 3200 RPM. This is my only real complaint I have on the car is that it is spinning kind of high for a normal speed. it still does 28-29MPG avg over the course of a tank so I guess I cannot complain too much.

 

[Boomyal]

Re: 5 and 6 speed automatic transmisions?

My Mazda 6 has a 6 speed manual (with a 2.5l I4). When crusing at 70mph I am running about 3200 RPM. This is my only real complaint I have on the car is that it is spinning kind of high for a normal speed. it still does 28-29MPG avg over the course of a tank so I guess I cannot complain too much.

That seems pretty high an RPM for 6th gear? My wife's Lincoln (3.9L V8) with a 5 speed automatic is only doing about 2k rpm at 70 mph.

 

[Thalasso]

Re: 5 and 6 speed automatic transmisions?

I have an 2011 GMC Arcadia that I am told has a 6 speed transmission. When driving above about 50 mph, sometimes there is a hesitation when accelerating. The dealer says that it is "normal" because of the 6 speed transmission downshifting. Twice it appeared that the transmission just shifted into neutral with the engine rpm jumping to over 6K and no acceleration of the vehicle.

Needless to say that I'm not happy with that.

Sounds like typical GM torque converter not locking up.

 

[jtmarten]

Re: 5 and 6 speed automatic transmisions?

My '97 850Ci has:
1st 3.55:1
2nd 2.24:1
3rd 1.54:1
4th 1.00:1
5th 0.79:1

Final drive 2.81