Why do you Cummins guys want more gears

Shiner, this inane argument with 4x will continue until he finally isn’t bored any longer....but you already know that. Your answer is correct and he is already chewing on the best leading,passive antagonistic responses he can muster

Must still have cabin fever up there in Alberta.....no ice off yet?

Or to 4x, I’ll answer a question with a question. Why do you care? And why did you just buy a 10 speed? Lol

Engines that are not working at full throttle can compensate for too high of gear ratio by substituting torque for RPM. When you are running near full throttle much of the time you can really notice power drop off when the transmission goes up a gear.

Most of the people here are using pickups that are generously powered for the load that they are moving. On the other hand, the Cummins in my motorhome is moving 30,000lbs with only 300hp and 600lb-ft of torque. Whenever the transmission upshifts to 4th or 5th gears I lose nearly a third of my RPM and a lot of my acceleration or hill climbing. I would dearly love to have another gear in that range as well as a lower first gear so things would get moving a little more quickly while waiting for the turbo to wind up.

So yeah, I would love to have 8 to 10 gears to choose from. Or 400hp and 900lb-ft or torque. Either would accomplish a lot.

4x4ord wrote:

ShinerBock wrote:
Same reason why 18 speeds are better than 10 speeds in class 7-8 trucks. More gears give you more opportunities to be at the right rpm for power/efficiency at different driving speeds. When towing really heavy in a 10-speed semi going up hills, you are more limited on your speed because the large step down to the next gear may not put you in high enough rpm to make enough horsepower. In the same truck/engine towing heavy in an 18-speed, you are less limited since you have more gear options making the step to the next gear much less and therefore putting you at a better rpm to make enough horsepower for higher driving speeds.

It is just like the 6-speed F350 versus the 10-speed F350. Towing heavy up a hill with a 3.55 F350 6-speed, you may be limited to 55 mph in 3rd at 2,800 rpm because up shifting to 4th would put you down to 2,000 rpm where you are making much less horsepower. It may be too much of a step in this scenario and you start to lose speed every time you shift to 4th. Therefore you are limited to around 55-60 mph.

In the 10-speed, 5th gear is close to 3rd in the 6-speed and 7th gear is close to 4th in the 6-speed. This means that 6th in the 10-speed is right in the middle so instead of dropping 700 rpm in the 6-speed, you only drop 300 rpm in the 10-speed which puts at a higher rpm to make more power and are not as limited to certain speeds as you are with fewer gears.

It can be nice having more gears. With the Duramax what your aying is a big deal. The Cummins has a pretty flat power curve so bumping the rpm up is not going to buy you as much. Most RVers who tow, say a 16000 lb fiver, will seldom hit a hill that will pull them down below 60 mph which is 2350 rpm in 4th gear with 3.73 gears. But for the one or two times a year they hit an 8% grade they will spend a moment or two with the engine running between 2350 and 2150 before the transmission drops from 4th to 3rd. At 2150 the Cummins makes about 401 HP and at 2350 it can produce about 414 HP. So having a gear 1/2 way between 3rd and 4th would allow the engine to run in the range of 413 to 420 as compared to 401 to 420.... it does buy you something on the odd hill.

There is some things I like about the 10 speed. In my Ford with 3.31 final and 1st gear at 4.62 my truck can put more torque to the rear axle in 1st gear than could a 2019 F450 with 4.30 gears. So getting going from a stop is incredibly easy. On the top end of the scale I like having the ability to lock out 1 or 2 over drive gears depending on what I am towing. If I'm bucking a wind I might lock out 10th; windy and hills I can lock out 10th and 9th. With the 6 speed there were times you didn't know whether to lock out 6th or not.

True, while most will never tow enough to warrant needing an 8 or 10 with a Cummins, apparently Ike times matter to many who decide on which is the best truck based on the times in those tests. I will also add that I have a ZF 8HP in my diesel car and I love it. It is not a slush box like both 6-speed transmissions are in the Ram and it is lighting quick on its shifts. I have never pulled anything to need 8 or 10 gears especially with the truck being tuned, but I would still like to have it over the current 6-speed slush box options.

ShinerBock wrote:
Same reason why 18 speeds are better than 10 speeds in class 7-8 trucks. More gears give you more opportunities to be at the right rpm for power/efficiency at different driving speeds. When towing really heavy in a 10-speed semi going up hills, you are more limited on your speed because the large step down to the next gear may not put you in high enough rpm to make enough horsepower. In the same truck/engine towing heavy in an 18-speed, you are less limited since you have more gear options making the step to the next gear much less and therefore putting you at a better rpm to make enough horsepower for higher driving speeds.

It is just like the 6-speed F350 versus the 10-speed F350. Towing heavy up a hill with a 3.55 F350 6-speed, you may be limited to 55 mph in 3rd at 2,800 rpm because up shifting to 4th would put you down to 2,000 rpm where you are making much less horsepower. It may be too much of a step in this scenario and you start to lose speed every time you shift to 4th. Therefore you are limited to around 55-60 mph.

In the 10-speed, 5th gear is close to 3rd in the 6-speed and 7th gear is close to 4th in the 6-speed. This means that 6th in the 10-speed is right in the middle so instead of dropping 700 rpm in the 6-speed, you only drop 300 rpm in the 10-speed which puts at a higher rpm to make more power and are not as limited to certain speeds as you are with fewer gears.

It can be nice having more gears. With the Duramax what your aying is a big deal. The Cummins has a pretty flat power curve so bumping the rpm up is not going to buy you as much. Most RVers who tow, say a 16000 lb fiver, will seldom hit a hill that will pull them down below 60 mph which is 2350 rpm in 4th gear with 3.73 gears. But for the one or two times a year they hit an 8% grade they will spend a moment or two with the engine running between 2350 and 2150 before the transmission drops from 4th to 3rd. At 2150 the Cummins makes about 401 HP and at 2350 it can produce about 414 HP. So having a gear 1/2 way between 3rd and 4th would allow the engine to run in the range of 413 to 420 as compared to 401 to 420.... it does buy you something on the odd hill.

There is some things I like about the 10 speed. In my Ford with 3.31 final and 1st gear at 4.62 my truck can put more torque to the rear axle in 1st gear than could a 2019 F450 with 4.30 gears. So getting going from a stop is incredibly easy. On the top end of the scale I like having the ability to lock out 1 or 2 over drive gears depending on what I am towing. If I'm bucking a wind I might lock out 10th; windy and hills I can lock out 10th and 9th. With the 6 speed there were times you didn't know whether to lock out 6th or not.

Our '16 Ram Cummins "performs" fine with a 6-speed. It rarely downshifts, even while towing. No real complaints. However, I recently drove a Ford PS and Chevy DM with the new 10-speeds. Hard not to notice how smooth and seamless the new trannys were. There may be more gears, but it seems like less. Is smooth and seamless necessary from a raw performance perspective, no. But, hard to argue with improved NVH. It's something even the average Joe would notice on a test drive.

valhalla360 wrote:

noteven wrote:
Because it is MOAR! speeds?

10 speeds and more are needed to optimize gas engines.

Why not use them in diesels too? Diesels don’t care.

While both types benefit...

Actually, the other way around, gas engines are happier over a wider range of RPM. If the engine is happy between say 1800-3500rpm, you can space the gears out more than if the engine is happy over 1500-2500rpm.

Of course really with modern engines, the power output is so great we are talking incremental improvements. Probably the biggest benefit is not having to mess around with a deep rear axle ratio for all but the heaviest trailers. It used to be a choice between good towing performance vs non-towing performance if you wanted to run in top gear. With 8-10 gears, the rear axle ratio is far less important and the truck will simply select the gear ratio it needs based on loading and speed.

I don't know much about little diesels, but I know all diesel do not have equal power bands. 318 hp Detroit & 13speed. Best performance, slam hand in door, keep it wide open. Tach drops below 1800? drop a gear, but it back to 2150. 300 HP Mack, 5 speed? Same load, 4:17 instead of 4:44 rear. Pull her down to 1200, neutral to wind her up to 2100 to put back in gear. NTC Cummins, 335 hp 13 & 4:44? Near same power band as Detroit except higher HP and torque. Would stay with Mack, but worked driver more. And if you wanted to hammer west across Kansas, better watch the Pyro or will burn hole in piston.
My experience tells me that more speeds in trans would only help if the engine could be tuned for better power/economy in a narrow band. And adding OD gears allows you to keep the lower speed rearend. And higher speed rears put more strain on everything but the axle shaft when starting a load.

There are two factors that I think many people fail to recognize about the Cummins/ Aisin combination. One is that the over all speed range of the Aisin 6 speed is very close to the Ford 10 speed. That is, 6th gear in the Aisin is the same ratio as 10th in the TorqShift and 1st gear in the Aisin is half way between 1st and second on the Ford 10 speed. The second factor is that the new Cummins has tremendous torque rise so it can handle much wider gear spacing than can the Duramax or Powerstroke without sacrificing performance.

When pulling a heavy trailer up a hill the required rear wheel torque is largely dictated by the incline of the hill and weight of the truck and trailer. As the truck slows down the power requirement is reduced but the rear wheel torque requirement doesn’t change much. If an engine has little torque rise, such as the Duramax the truck will continue to slow down until it can grab the next gear to raise the rear wheel torque in order to meet the demands of the hill. The Cummins on the other hand is able to produce much more torque as it pulls down so a gear change may not be necessary. For every 100 rpm the Cummins looses in rpm it gains nearly 29 lbft of torque compared to 10 lbft rise in torque per 100 rpm for the Duramax.

I think it is nicer pulling a hill using the engine’s torque rise vs having more gears and constant shifting up and down.

ShinerBock has the correct answer. :C

True no matter the brand.

Same reason why 18 speeds are better than 10 speeds in class 7-8 trucks. More gears give you more opportunities to be at the right rpm for power/efficiency at different driving speeds. When towing really heavy in a 10-speed semi going up hills, you are more limited on your speed because the large step down to the next gear may not put you in high enough rpm to make enough horsepower. In the same truck/engine towing heavy in an 18-speed, you are less limited since you have more gear options making the step to the next gear much less and therefore putting you at a better rpm to make enough horsepower for higher driving speeds.

It is just like the 6-speed F350 versus the 10-speed F350. Towing heavy up a hill with a 3.55 F350 6-speed, you may be limited to 55 mph in 3rd at 2,800 rpm because up shifting to 4th would put you down to 2,000 rpm where you are making much less horsepower. It may be too much of a step in this scenario and you start to lose speed every time you shift to 4th. Therefore you are limited to around 55-60 mph.

In the 10-speed, 5th gear is close to 3rd in the 6-speed and 7th gear is close to 4th in the 6-speed. This means that 6th in the 10-speed is right in the middle so instead of dropping 700 rpm in the 6-speed, you only drop 300 rpm in the 10-speed which puts at a higher rpm to make more power and are not as limited to certain speeds as you are with fewer gears.

SweetLou wrote:
Not needed. More speed towing is dangerous for many reasons, and you achieve a good speed now. Lugging any engine while pulling a weight not good either. Continual searching for correct gears can't be good. The best overall range for towing with that Cummins is around 1800 RPM so in my opinion not needed.

Most of what you said is an argument FOR more gears.

Lugging is certainly not good for the engine. You need more gears to keep the engine in the ideal RPM range over varying conditions.