8 Speed Auto for HD trucks

Me Again wrote:
Maybe Diesel/Electric will take over like Locomotives and Ships!

I agree. All the improvements are a step closer to going electric.

Me Again wrote:

Rebuilding a 47RE cost around 3-4K. Rebuilding a 6 speed 68RFE cost 7-8K. Not sure on Aisin, as I have not heard of a rebuild. Rebuilding a 6R140 or Allsion 1000 6 speed are similar in the 7-8K range.

Image what a 10 speed will cost to rebuild!!!!

And an E40D or 4L80E cost what, 1500-2k to rebuild/replace? But you aren't saying you want one of those.

Just like now, if you want cheaper maintenance costs, you buy an older truck.

I see your point, but I don't think 6 speeds it the limit for "light" HD trucks, or whatever they are called. I do agree there is a point of diminishing returns for adding gears, since you can only control so much weight with vehicles in this class.

Technology marches on, and unfortunately gets more expensive along the way.

parker.rowe wrote:
If they can make a 10 speed transmission with the required torque rating, I'm not sure why you would argue that you want less ratios to choose from for varying grade hills, headwinds, hauling weights, etc.

EDIT: Based on current 10 speeds, I would guess max overdrive will stay the same for the most part. But you will have less gear spread and much lower low gears without big gaps between them.

Just because you don't NEED it now, doesn't mean it isn't better.

I think its a great idea, gas or deisel.

Rebuilding a 47RE cost around 3-4K. Rebuilding a 6 speed 68RFE cost 7-8K. Not sure on Aisin, as I have not heard of a rebuild. Rebuilding a 6R140 or Allsion 1000 6 speed are similar in the 7-8K range.

Image what a 10 speed will cost to rebuild!!!!

as a point of interest because its not apples to apples, my volvo has a 12 speed (automated with 2 reverse)but never uses all the gears.
It can sense the load (very light) starts in 3 almost 99% of the time then skips the next 1 or 2 gears.These new transmissions may do the same, they have every possible gear for all conditions.
Does anyone know it they skip shift?

If they can make a 10 speed transmission with the required torque rating, I'm not sure why you would argue that you want less ratios to choose from for varying grade hills, headwinds, hauling weights, etc.

EDIT: Based on current 10 speeds, I would guess max overdrive will stay the same for the most part. But you will have less gear spread and much lower low gears without big gaps between them.

Just because you don't NEED it now, doesn't mean it isn't better.

I think its a great idea, gas or deisel.

For big trucks, the gear count came down not up as engine tuning increase the power ban in some cases. We had 5x4 and 5x3 transmission setups with a 5 speed main tranny and a 4 or 3 speed brownie. Creating 20 or 15 forward gears. Then the 13 speeds in one box, down to 9 as power bans increase in widths. Eaton Autoshift has 18 gears forward a 4 in reverse, and a clutch to start moving, not a torque converter.

It is a mixed bag depending on application.

Here is a write up on what is happening in heavy duty trucks.
https://www.truckinginfo.com/154981/transmission-trends

For pickups going from 4 speed autos to 6 was a great improvement. Ford and GM/Allison started in 2000ish with 5 and switched to 6. I am not sure in the HD pickup arena the that going to 8 or 10 will make a large improvement like going to 6 did.

For a hand full of users like Cummins12V98 having another OD for freeway cruising would be a benefit, however delivering power via a .50 to 1 third overdrive might be self defeating.

The question remains do diesel trucks need more gears within the same range as the 1-6 ratios that we have now. For my use, the answer is no. Better programming to assure the combination was always in the best gear for the conditions might be more beneficial than more gears(that would require similar programming to be effective).

The RAM/Cummins in the pipe line(for 2019 r 2020 models) with all smog stuff down stream of the engine, might be a much bigger improvement to mileage than any transmission change.

Ralph Cramden wrote:
The end ratio of high gear is going to be in the neighborhood of 0.68/1 no matter if it's a 6 speed or a 20 speed. Assuming we're talking HD gassers, which hit their powerband at a high rpm, other than squeezing an almost impossible to notice MPG gain the extra gears don't give you all that much.

Now in a truck that's used by Joe Schmow to haul a couple of bags of mulch between work commutes, or Soccer Sally to haul home the groceries, which are what the vast majority of light duty trucks are used for it makes all the sense in the world to have some extra ranges between top and bottom. In a HD truck being used as an HD truck it does not make as much sense. I suspect I am getting an 8 or 10 speed through no choice of my own the next time I buy a truck, but my current 2015 GMC 2500 with its 6 speed has more than enough intermediate gears, I don't know what I would be gaining with 2 or 4 more other than more heat from more shifts and additional parts to wear or fail internally. I was not looking for mileage when I bought it.

Lots of gears make more sense the larger the truck.
- Your average passenger car will rarely see much more than a 300-400lb variation in loading (0 to 3 passengers) with rarely any aerodynamic variations. That's within 10% of the overall weight, so not a huge difference in power needs. The engineers can pick the best 3-5 gears and get it pretty well dialed in (more are still better but have less impact).
- Your average truck experiences wildly different loading and aerodynamics. My 3/4 ton starts out just over 6,000lbs but if I fully load bed, I can push close to 9,000lb (50% increase). If I hook up the 5th wheel, I can be up around 18,000lb (200% increase) total with almost twice the frontal area making for drastically worse aerodynamics. The same truck can be anywhere in-between. (commercial trucks can be even worse) If you have a limited number of gears, it's hard for the engineer to pick a set that works well for every combination of loading, so more gears allow a better match.

wilber1 wrote:

Me Again wrote:
Maybe Diesel/Electric will take over like Locomotives and Ships!

Basically that is the Volt, except it isn't diesel and it has a battery pack to store energy.

The Volt is a drastically different solution from a diesel/electric train even though there are some parallels the reasons and benefits have little to do with each other.

Trains: Steam engines (similar to electric motors) could deliver maximum torque from zero RPM. Also you could manage the power delivery very well and you didn't have the issue of stalling the engine like with an ICE. As diesels came out and grew in HP and you moved to multiple engine trains, development of a mechanical transmission that could handle the massive HP and coordinate between multiple engines while keeping the diesel in a very narrow power band quickly became impractical. So even though it was less efficient (compared to a mechanical transmission once up to speed), the losses were small enough that using a generator and electric motors as the transmission was better since it allowed that max torque at zero RPM, allowed you to keep those big slow turning diesels at the ideal RPM and made it simple to coordinate multiple engines via electronic controls. (trains more than make up for any efficiency losses by using ultra low rolling resistance wheels and aerodynamic benefits of 5' headways). The generators/electric motor function almost exclusively as a transmission.

Volt: The Volt does have a function that will do gas-electric operation but it's a backup function and much less efficient operation. Ideally, the Volt will run 80-90% of the time on battery electric and the gas-electric operation is only rarely used. The gas-electric mode is only a backup for those (ideally) rare times when the battery runs down. Once in gas-electric mode, efficiency drops below what an equivalent standard ICE car will provide. As long as it's a rare situation, it's a good trade off.

It's unlikely to take over the truck market as we have mechanical transmissions that can easily handle 80,000lb trucks. For our little non-commercial trucks it's not even close to pushing the limits. Then you have the weight and space considerations. Your transmission isn't really that heavy compared to a large generator and electric motors. It's possible we will see a Volt type setup but it will likely be focused on light duty grocery getter 1/2 ton trucks that rarely do any significant towing. If you get a 40 mile range under battery (similar to the volt), once you hook up a big trailer, that will likely be under 20 miles and most camping trips are far beyond that range, so within the first 15-20 minutes of driving, you will switch to the less efficient operation.

Me Again wrote:

valhalla360 wrote:
And the old guys probably said the same thing when automatics went from 2 to 3 gears.

CVT's used in trucks will be nothing like the snowmobile transmissions. Of course they aren't going to use a simple rubber belt for a truck towing 15k lbs. That's also why they haven't put the trucks out with CVT's yet but I can guarantee someone is working on it.

PS: Just looked up and there is a consortium of semi tractor manufacturers working on one.

OK, so in 1976 to 1979 I drove a truck with a 13 speed Roadranger tranny. Along came people have did not know how to drive a manual tranny, so Firetrucks and garbage trucks got automatics. The CVT trannies will complete the circle. BTW, I really liked the 13 speed, let the clutch out in the tank yard in Port Angeles and put it back in at Forks 70 miles away! With lots of shift in between.

Chris

I think manuals stuck around in HD trucks for longer because the driver wasn't paying for the truck in most cases. The guy buying the truck didn't have to work those gears. As long as they held up well and were cheaper to purchase, that's what you got.

Now you will probably hear a lot of old truckers say they love manually running the gears but that's likely selection bias. If you hate driving a manual transmission, odds are you aren't going to keep a job that has you driving a manual transmission 8-10hrs per day.

Most personal vehicles are bought by the guy driving it and if they don't like a manual, they don't buy a manual. Looking at the number of manuals available, it's pretty clear most people don't want a manual.

Ralph Cramden wrote:
The end ratio of high gear is going to be in the neighborhood of 0.68/1 no matter if it's a 6 speed or a 20 speed. Assuming we're talking HD gassers, which hit their powerband at a high rpm, other than squeezing an almost impossible to notice MPG gain the extra gears don't give you all that much.

Now in a truck that's used by Joe Schmow to haul a couple of bags of mulch between work commutes, or Soccer Sally to haul home the groceries, which are what the vast majority of light duty trucks are used for it makes all the sense in the world to have some extra ranges between top and bottom. In a HD truck being used as an HD truck it does not make as much sense. I suspect I am getting an 8 or 10 speed through no choice of my own the next time I buy a truck, but my current 2015 GMC 2500 with its 6 speed has more than enough intermediate gears, I don't know what I would be gaining with 2 or 4 more other than more heat from more shifts and additional parts to wear or fail internally. I was not looking for mileage when I bought it.

Some posters mentioned how well they like the 8-10 speeds in their cars or 1/2 tons, and I'm sure they work great, improving performance/mileage. However, Ralph makes good points, concerning HD truck use, even with a gasser.

Jerry