If There Were No Emissions Regs, Would A Six Speed Transmission Still Be "Necessary?"

[nicholastanguma]

IMO, a six speed transmission is ideal for almost all vehicles. Fewer is limiting, more is constantly gear hunting or changing 5 times from 0-30 mph. My favorite engines have all been slightly oversquare (stroke about 75% of the bore), large displacement per cylinder, with both low end torque and heads that allow higher RPM airflow. What you end up with is something that can be lugged and short shifted, (or just not shifted) as well as something that that can be revved out and driven fast and hard.

The more time I spend with this subject the more I am becoming convinced everything in this paragraph is 100% spot-on.

 

[nicholastanguma]

Are they? And if so, why?

Complaining about highway revs being too high.

I've only ever owned one car with a 5 speed, and 5th gear was pretty much just for highway use. I'm not sure what advantage, if any, a sixth gear would offer a vehicle. I think the big reason we have so many gears now is really because of traffic, not for any inherent mechanical need.

By the 80's, 4 speeds wasn't sufficient for the demands of traffic. There is a hint of planned obsolescence about the whole adding more speeds to transmissions every decade, but really it's because the traffic, not the vehicle, demands it.

Traffic, yes, I agree with this. Planned obsolescence, I def agree.

 

[Mos6502]

Complaining about highway revs being too high.

For a few decades when three speeds was standard, fourth if offered, was the overdrive. You can have have the same spread of gearing between two gears as you can have with 10 gears. All we've been adding really is more intermediate gears. Partly because this improves city fuel economy, but mostly because with more cars on the road, it's no longer practical/safe to go up hills in 2nd, as you would have to do with an old three speed. You'd get too much traffic held up behind you/road ragers. Off-road there is another practical advantage of getting more flexibility in engine vs. ground speed, with a lot of old vehicles in the three and four speed era making you decide between going too fast or two slow when trying to match optimal engine speed to road conditions.

 

[nickw]

For a few decades when three speeds was standard, fourth if offered, was the overdrive. You can have have the same spread of gearing between two gears as you can have with 10 gears. All we've been adding really is more intermediate gears. Partly because this improves city fuel economy, but mostly because with more cars on the road, it's no longer practical/safe to go up hills in 2nd, as you would have to do with an old three speed. You'd get too much traffic held up behind you/road ragers. Off-road there is another practical advantage of getting more flexibility in engine vs. ground speed, with a lot of old vehicles in the three and four speed era making you decide between going too fast or two slow when trying to match optimal engine speed to road conditions.

Not necessarily true, we've also added a much lower 1st in many which is a huge benefit. I know the Powerwagons went from like 35:1 to 51:1 simply due to lower 1st gear ratio. Lower is not always better though as it may shift too often and a low 1st can be worthless if not annoying in everyday driving, I know in the case of the Ford it can use 2nd for a more traditional launch and skip intermediate gears if not needed, I honestly don't really know, it just works and I don't think about it.

Low 1st can be selected but a low final drive can't, so the new transmissions are great for offroading.

For reference, all 1st gear ratios, you can see the trend:
Ford 10 spd = 4.69
Powerwagon 8 spd = 4.7
LC200 8 spd= 4.7
LC200 6 spd = 3.33
Tacoma 6 spd = 3.6
Powerwagon 6 spd = 3.23
LC100 5 spd = 3.52
LC 80 4 spd = 2.95 / 2.8
Turbo 350 3 spd = 2.52
Powerglide 2 spd = 1.82

 

[Metcalf]

For a few decades when three speeds was standard, fourth if offered, was the overdrive. You can have have the same spread of gearing between two gears as you can have with 10 gears. All we've been adding really is more intermediate gears. Partly because this improves city fuel economy, but mostly because with more cars on the road, it's no longer practical/safe to go up hills in 2nd, as you would have to do with an old three speed. You'd get too much traffic held up behind you/road ragers. Off-road there is another practical advantage of getting more flexibility in engine vs. ground speed, with a lot of old vehicles in the three and four speed era making you decide between going too fast or two slow when trying to match optimal engine speed to road conditions.

In automatics we have been adding greatly to overall gear spread on both ends. Most historic 3 speed autos where about a 2.5:1 first and a 1:1 3rd. Now we are seeing 4-5:1 first gears all the way to .6X 6-10th gears. And that works WAY better overall.

I recently built a older style Toyota Land Cruiser with a modern 2013 GM 5.3 aluminum LC9 engine and 6L80E transmission out of a pickup. It is a fantastic all around combo on and off-road. It let me use a much more mild low range while still maintaining good 'crawl' ratio performance.....and I can still run 50+ mph in low range for sand, desert, and mud.

 

[nickw]

In automatics we have been adding greatly to overall gear spread on both ends. Most historic 3 speed autos where about a 2.5:1 first and a 1:1 3rd. Now we are seeing 4-5:1 first gears all the way to .6X 6-10th gears. And that works WAY better overall.

I recently built a older style Toyota Land Cruiser with a modern 2013 GM 5.3 aluminum LC9 engine and 6L80E transmission out of a pickup. It is a fantastic all around combo on and off-road. It let me use a much more mild low range while still maintaining good 'crawl' ratio performance.....and I can still run 50+ mph in low range for sand, desert, and mud.

View attachment 575358

Or if you are more inclined to stay offroad....you can use that OD of the trans to allow the use of numerically higher final drive ratios without giving up top speed vs the older 3-spds.

Cool truck.

 

[Todd n Natalie]

While it looks like 26 speeds you cannot use every combination. 18 useable combinations.


I'm retired but I keep my Class I just in case the opportunity arises to drive one.
Armstrong steering to.

That's crazy. I have no idea what was going on there.

 

[nickw]

There's some other wizardry that can happen, like for example the RFE (again, a 6 speed transmission, I've had it in two vehicles so far which is why I'm familiar) was initially sold as a 4 speed because 6th gear simply wasn't programmed in as an option and 3rd gear was really only an alternate 2nd gear that the transmission could downshift to from "3rd" but not upshift to from 1st or true 2nd. The ratios for 2/3 and for 5/6 are really close in the light duty variant of that transmission so it's maybe more akin to a.. um.. 5.75 speed

On Jeep Patriot when equipped with what they called Freedom Drive II the CVT would provide a super low initial ratio (including the final drive) of 19:1 without a low range transfer case. That's not a super impressive crawl ratio by rock crawler standards but it's almost 2x lower than my truck's would be without a transfer case. By not running a transfer case or center differential they could make the whole vehicle a lot lighter and more affordable and fuel efficient.

That CVT is probably a cool setup for a mild offroader if you had a locking center diff. I've also heard some of those CVT "mimic" std. trans with set points, so instead of ramping continuously, they have definitive ratios they'll hold akin to a std. auto....

 

[Deleted member 9101]

That CVT is probably a cool setup for a mild offroader if you had a locking center diff. I've also heard some of those CVT "mimic" std. trans with set points, so instead of ramping continuously, they have definitive ratios they'll hold akin to a std. auto....

My wife had an Altima that did that. It gets rid of that "when is it gunna shift" feeling.

 

[billiebob]

That's crazy. I have no idea what was going on there.

Think of it like an 18 speed mountain bike. 2 transmissions, the crank with 3 sprockets, the wheel with 6.
In a truck the most common was a 5 speed main, technically the same as a mountain bikes 6 sprockets,
and a 4 speed auxiliary functioning like the 3 speed crank sprocket. Most shifting is done thru the 6 rear wheel sprockets.

You are never on both small sprockets nor both large sprockets since that puts stress on the chain and is not efficient. Same with a truck. You would never be in 1st gear and overdrive nor 5th gear and bull low. But shifting creates several gear overlaps requiring shifting both transmissions together to get the correct ratio.

So in Bull Low one shifts thru 1st, 2nd, 3rd then shifts up to Low and 2nd, 3rd, 4th before shifting the auxiliary transmission to Direct and shifting thru 3rd, 4th, 5th, and finally hitting Overdrive to shift thru 4th and 5th. The real challenge was doing this on roads no where near as nice as todays, with loads often heavier than hauled today, and with half the horsepower trucks have today. When men were men and women were cupcakes.

 

[nickw]

Think of it like an 18 speed mountain bike. 2 transmissions, the crank with 3 sprockets, the wheel with 6.
In a truck the most common was a 5 speed main, technically the same as a mountain bikes 6 sprockets,
and a 4 speed auxiliary functioning like the 3 speed crank sprocket. Most shifting is done thru the 6 rear wheel sprockets.

You are never on both small sprockets nor both large sprockets since that puts stress on the chain and is not efficient. Same with a truck. You would never be in 1st gear and overdrive nor 5th gear and bull low. But shifting creates several gear overlaps requiring shifting both transmissions together to get the correct ratio.

So in Bull Low one shifts thru 1st, 2nd, 3rd then shifts up to Low and 2nd, 3rd, 4th before shifting the auxiliary transmission to Direct and shifting thru 3rd, 4th, 5th, and finally hitting Overdrive to shift thru 4th and 5th. The real challenge was doing this on roads no where near as nice as todays, with loads often heavier than hauled today, and with half the horsepower trucks have today. When men were men and women were cupcakes.

Great analogy - never thought about comparing to a bike.

 

[Mos6502]

Not necessarily true, we've also added a much lower 1st in many which is a huge benefit. I know the Powerwagons went from like 35:1 to 51:1 simply due to lower 1st gear ratio. Lower is not always better though as it may shift too often and a low 1st can be worthless if not annoying in everyday driving, I know in the case of the Ford it can use 2nd for a more traditional launch and skip intermediate gears if not needed, I honestly don't really know, it just works and I don't think about it.

Low 1st can be selected but a low final drive can't, so the new transmissions are great for offroading.

For reference, all 1st gear ratios, you can see the trend:
Ford 10 spd = 4.69
Powerwagon 8 spd = 4.7
LC200 8 spd= 4.7
LC200 6 spd = 3.33
Tacoma 6 spd = 3.6
Powerwagon 6 spd = 3.23
LC100 5 spd = 3.52
LC 80 4 spd = 2.95 / 2.8
Turbo 350 3 spd = 2.52
Powerglide 2 spd = 1.82

The '68 Saab I'm working on (as in my avatar) has a 3.56 first, and 4.88 final drive. And such short legged gearing was not unusual in prewar cars. 0.83 for fourth, so the spread of ratios is pretty big (although, not really big enough with such a highly geared final). Old automatics weren't built with efficiency in mind, and really, for decades maintained the Model T school of thinking that torque from the engine is more cost effective than gears in the box. But manual boxes usually had a larger spread of gearing.