it's all about gears!

[royanddoreen]

Originally Posted by mcrews

Drove my gf 2011 Lexus RX 350 for several days this week.
It has an 8 speed automatic transmission.

What a difference compared to the Kia's 5 speed automatic tranny.

Given my personal experience w/ upsizing to lower rpm and the joy of driving an 8 speed, I can't understand why the industry has been so slow in increasing the gearing in their eco-models.

I remember the 1984 corvette had the first 6 speed and got 27mpg on the hwy all day long.

I really thing 6-8 speed auto trannies are the secret to improving mpg.

I'm so much thinking the same way about gearing!! upsized tires on my car 1.5 inchs higher than stock enjoying the lower rpms on my drives.

[user removed]

In 1968 my 59 AH Sprite was good for a penny a mile. Today the bike is 4 pennies a mile.
84 sentra diesel 4 speed epa was better than the 5 speed.
regards
Mech

[vskid3]

I loved my GTO's 6 speed manual. 1st-4th were meant as the power gears, 5th and 6th for mileage (both were overdrives). 4th could go up to 130MPH, and 6th would do 75MPH at under 2000RPM and still pull quite nicely.
I don't really care how many gears there are, just as long as they provide adequate acceleration and a top gear that is as high as the engine can reasonably handle.

[cRiPpLe_rOoStEr]

Originally Posted by vskid3

I don't really care how many gears there are, just as long as they provide adequate acceleration and a top gear that is as high as the engine can reasonably handle.

The problem is that nowadays the manual transmissions are getting the ratioes too close, more focused on a "sporty" feeling than in an overall efficiency. But who says a 4-speed would gonna be less "funny" than a 6-speed, right?

Anyway, less gears with better ratioes actually improve both the reliability and the fuel-efficiency, since there would be less clutch wear (due to a lesser amount of gear changes required for the engine to operate in a reasonable speed), less internal frictions in the transmission, and a little lighter weight. What would be so bad about a 4-speed in, let's say, a Corolla?

[mcrews]

Originally Posted by cRiPpLe_rOoStEr

Anyway, less gears with better ratioes actually improve both the reliability and the fuel-efficiency, since there would be less clutch wear (due to a lesser amount of gear changes required for the engine to operate in a reasonable speed), less internal frictions in the transmission, and a little lighter weight. What would be so bad about a 4-speed in, let's say, a Corolla?

don't mean to get snarky.....but what you just said flys in the face of what the industry is doing.
And even though the industry is full of untrained and uneducated idiots, could you please show some FACTUAL PROOF of what you are saying....


(because an 8 speed Lexus automatic transmission is good for 150-200,000 miles)

[P-hack]

more idling gear meshes is an issue w/constant mesh transmissions, true, though with computer precision doing the actual engagements, I think sliding mesh should be revisited.

more gears=more clutch wear? nah. If you get a lower first gear out of the deal you will actually save more clutch as getting rolling is where the wear is at normally (and where %100 of the wear is at if it shifts automatically).

[serialk11r]

Originally Posted by P-hack

more gears=more clutch wear? nah. If you get a lower first gear out of the deal you will actually save more clutch as getting rolling is where the wear is at normally (and where %100 of the wear is at if it shifts automatically).

Exactly, gear changes are extremely easy on the clutch compared to starts and closer ratios could mean less clutch wear per shift.

I think the idling gear meshes could be mitigated with smarter oiling. As I understand a lot of transmissions have the gears completely bathed in oil. Even if that's wrong, I don't think idling gears consume much power, and the weight penalty isn't even that bad. The Toyota C60 for example is only 10 pounds more than the C5x transmissions, which is less than the weight of the extra clutch packs and pumps of an automatic transmission alone or solenoids in a DCT/SMG.

My driving is half city/stop and go, half highway cruising so I value closer ratios, but people who live further from cities and do more constant speed driving would understandably not mind having less gears as long as the highest gear is good.

[rmay635703]

Originally Posted by mcrews

don't mean to get snarky.....but what you just said flys in the face of what the industry is doing.

Gears are a gimmic, sort of like adding mystery oil to your gas, they have their purpose, especially in terms of lame brain automatics but the reality is that the gains in MPGs that I see between historic WELL BUILT 4 speed OD Autos and these 7,8,9 speeds is that there has been little or no gain. There is obviously a gain but generally the transmissions are coupled with even larger, heavier options. Only place I see this as being good is around town but only if the car will upshift as high as possible.

The key to understand is that what is MOST EFFICIENT, AKA a direct drive manual transmission with few moving parts, is NOT the most efficient at all loads and would also affect acceleration and performance in various bands.

All this said I like having a well designed 5 speed manual with a WIDE set of ratios, a 4 would likely work as well.

Originally Posted by mcrews

(because an 8 speed Lexus automatic transmission is good for 150-200,000 miles)

I fail to see how that is "good" or applicable to this conversation, all autos I've owed excluding ones that "needed replacement" on purchase of said vehicle have lasted that long, but then again I avoid Dodge and Ford and 80's chevy OD XMSNs.

Lately I won't own autos, exception would be a Prius or a Volt where there is not alternative.

[serialk11r]

I think it's not a gimmick though. Toyota is pairing the 1NR-FE with a wide ratio 6 speed in non-US markets, and that thing only has barely over 100hp. 5 speeds I can see being okay with a 1L engine or something like that, but a 6 speed makes a lot of sense for basically all US market engines and a 7 speed makes sense for sporty cars with potent engines (e.g. Honda S2000 cruises at 4000rpm, even if you spaced out the gearing like an eco car you would not be running very reasonable rpms).

Obviously this is a fuel economy forum but closer ratios in a manual transmission does make it easier to shift and more enjoyable to do so, and it is also good for performance. More gears is better, if you're talking stick shift. Automatic, I don't really care because I'd rather have a Toyota Hybrid eCVT, or series hybrid, but if the industry thinks 8 speed autos aren't hard to make and are worth it then they're worth it.

[cRiPpLe_rOoStEr]

Originally Posted by mcrews

don't mean to get snarky.....but what you just said flys in the face of what the industry is doing.
And even though the industry is full of untrained and uneducated idiots, could you please show some FACTUAL PROOF of what you are saying....

I have seen it in some Fiat and Volkswagen compact cars, including the U.S.-spec Fox which retained the same 4-speed gearbox of the earlier versions of the Volkswagen Voyage on which it was based, also retained by the cargo versions of the Gol due to reliability until they were phased out in '96. During the 80s the fuel-saver transmission for the local Volkswagens back here was the 4-speed, in spite of a 5-speed being available at least since '85 for the front-engined ones.