Should I buy a 2012 or wait for the 2013?

[Jim W]

The 3. 42 gears are there to squeeze a fractional MPG gain for the government's CAFE requirements, not to enhance the towing capabilities or experience. They will effectively render 6th gear useless for towing, unlike the 4. 10s. Not a good match for towing with double overdrive automatics.

Rusty

Rusty
What are you basing this on the gear ration in the 68RFE of the 2007. 5 to the 2012 MY trucks or the gear ratios of the 2013 MY trucks in the transmission. I have not seen these ratios published yet but I believe Ram has provided design improvements of the 2013 trucks over the other MY trucks. Such as and I quote; “For 2013, all Ram Heavy Duty diesels benefit from an all-new cooling system. A high-efficiency fan, dual radiators, dual transmission coolers and low-slung charge air cooler afford 25 percent more heat-rejection capacity. Lower operating temperatures deliver improved performance, durability and lower operating costs. Cummins Turbo Diesel-equipped Ram trucks also provide best-in-class 15,000-mile oil change intervals. ” From TDR press release.

I am a retired engineer from Cat and I have learned over the years not to second guess what other engineers have designed for different products. We all have different design parameters to work with and these change with every new model design that the engineer works on. Functional specs are always changing by the marketing department At least at CAT and this is what we always design to.

Jim W.

 

[BILLUA]

To the OP: I was faced with a similar choice as you. I went with the 2012 and have not regretted it one bit. You will be amazed at the improvements to these trucks.

 

[Gonzo 1066]

Just a little lession on gearing, In ANY transmission the direct gear is the most efficent transmission of power. In the manual 6 speed 5th gear is a direct gear (power does not drop to the countershaft) thus the most efficent ( and strongest) transmitter of power. In the new automatic with two overdrive gears that would make 4th gear the most efficent gear to transmit the most power. I would have to assume that when the RAM engeneers went to the 3:42s they just reprogramed the trans computer to shift down to the more efficent gears to make this system work. The limiting factor is NOT the differentail gear set, it is the transmission.

 

[RustyJC]

Rusty

I am a retired engineer from Cat... ... .

OK, and I'm an engineer about to retire after 40 years service from the power and compression division of Cameron - the group that builds Cooper-Bessemer, Superior, Enterprise and other large industrial engines and compressors. Let's wait until some of the 3. 42-equipped trucks hit the roads in towing applications and see what happens.



My point was that if the transmission winds up in 4th for the majority of the time, one is effectively working with 3 gear splits when towing (1-2, 2-3 and 3-4), not the 5 gear splits that those of us with 4. 10 gears can use during acceleration, hill climbs, starting from a stop, steady state Interstate cruise and other such situations. It sort of eliminates the advantages of a 6 speed transmission, doesn't it? As far as available transmission ratios are concerned during towing, it's like being back in the 47/48RE days.



Rusty

 

[NIsaacs]

The limiting factor is NOT the differentail gear set, it is the transmission.

I agree with your assessment of the manual transmission but the auto is different. All gears in the auto are straight through, no counter shaft. The Ford 6 speed auto don't even have a direct, 4th is an under with 5th and 6th both overs.



Since there are no options with the transmission, that fact is a given, but since there are or used to be rear axle options, that fact can make a more efficient combo.



Nick

 

[AH64ID]

Jim you also have to account for the marketing aspect of those releases. Lower operating temperatures generally lead to lower performance, but it all depends on what you mean by lower. The 200° thermostat in the 4th gens is there to help with mileage, so, in theory, a 190° would get worse performnace/mileage. So I take everything in a press release with a grain of salt.

The 2500 is keeping the 68RFE correct? The 2500 is also staying with 800 ft/lbs, so same trans and same power with 3. 42's means less torque to the wheels, especially when getting a load going. The hp on the '13 is increased to 370, but that won't effect the torque until the upper rpms. The '13 is also rated at 2800 rpms and not 3000, but looking at the HO chart for 11. 5+ the tq at 2800 is 610 ft/lbs. The '13 will produce about 85 ft/lbs more torque in the upper rpms, so let's see if that is enough to overcome the 20% gearing change.

Peak torque is 1600 rpms, so assuming a locked converter (I know it doesn't lock in 1st) here are some numbers, this also doesn't take torque management into account, it's simply meant to show the difference gearing makes. Speed assumes the 265/70/17, the option 18" tire/wheel combo for the '13 will increase speed and reduce gearing further.

#ad


Take it for what it is, an example of torque to the ground at rated torque and hp rpms.

As you can see the 3. 42's are a gear behind in power, so 6th does become useless when towing (other than long down hills) and that's fine as the trans will probably like the lower gearing, but what you lose is that stump pulling torque of 1st and 4. 10's. Like I said that may not effect some people, and others it will be noticeable. Will the 3. 42's get better mileage at 85 than 4. 10's, maybe but at the speeds that they are "efficient" at the wind resistance is what kills mileage and not rpms.

Just a little lession on gearing, In ANY transmission the direct gear is the most efficent transmission of power. In the manual 6 speed 5th gear is a direct gear (power does not drop to the countershaft) thus the most efficent ( and strongest) transmitter of power.

Lot's of people post that, but I don't believe that it's true. 1:1 does create the least amount of heat because there is no torque multiplication (or division in OD), but you MUST use the countershaft. The only way to get power from the input to the output is via the countershaft. If the input and output were connected without the countershaft then you would only have 1 gear, 1:1. You have to use the gears to get power from the input to the output, 5th just does it at a 1:1 ratio.

 

[Gonzo 1066]

In both the NV 4500 and the NV 5600 there is a direct gear. This drives the power through the top shaft of the transmission without using the countershaft. Thus a 1:1 ratio. If your engine is turning 1900rpms then the driveshaft is aslo turning exact engine speed (1900rpms) The same as any automotive 4 speed transmssion (muncie or the Chrysler 833) the top gear is direct. Transmission efficency is as high as it can get when there is not over or underdrive going on, this is why there is more heat generated in any transmission the deeper the drop or rise of ratio.



Sorry I just re read your post, yes even in direct gear the countershaft is turning, however t is not transmitting power in direct gear that power is transmitted from imput shaft to output shaft without dropping to the countershaft.



After saying all of this I do agree, depending on useage a lower rear gearset would be better for the dedicated towing truck. It seems that the majority of the Diesel trucks on the road only tow on occasion. In this case a "cruser gear" would be a real advantage in MPGs.

 

[AH64ID]

If it doesn't drop to the countershaft why is there a 5th C/S gear?

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[RustyJC]

Ummm... . towing in 6th gear @ 65 MPH on the Interstate, my 68RFE runs about 160 to 165 degF per the EVIC. I don't particularly see transmission fluid heat generation or buildup as a limiting factor in my application.

 

[JSoloman]

This is all great information. It helps to weigh out what is the most important use of this rig. For me, it's for hauling and towing. I have car for running to the grocery store and use public trans to get to work. History tells me that on the back hilly graveled road and mountain passes, I am still stuck on the 4:10 rear end. So, my choices are few. Buy a '12 SRW or '13 DRW.

So, I've read plenty about the short mileage oil change intervals on the '10-12s, are you stuck with changing the oil when the warning comes up or could you ignore it and drive it til you get the the number of miles expected for the oil change? If so, what would be the down side doing that?

 

[AH64ID]

The algorithm assumes 5%, or close to, fuel dilution in the oil when the light comes on before 7500-8000 miles. There is supposed to be a 500 mile buffer, but I would change it at the earliest time possible. It is frustrating if you are on a road trip and cannot predict an oil change.

 

[Gonzo 1066]

I stand corrected, Assuming that the 5600 was the same as the other transmissions I have worked on put some egg on my face. Although the 5th gear is only a single drop.

 

[NIsaacs]

If it doesn't drop to the countershaft why is there a 5th C/S gear?



#ad

Typo maybe? The #A, 5th C/S gear, is actually only the C/S drive gear. Notice the 5&6 Assy, that is a shift collar, it is locked by splines to the main shaft. When it is slid back you have 6th, when it is forward you have 5th, in 5th the two shafts (input and output) are now locked together and make one, that is why it is called direct.



Nick

 

[Task125]

I went with 2013,want that engine trans combo.

 

[AH64ID]

Typo maybe? The #A, 5th C/S gear, is actually only the C/S drive gear. Notice the 5&6 Assy, that is a shift collar, it is locked by splines to the main shaft. When it is slid back you have 6th, when it is forward you have 5th, in 5th the two shafts (input and output) are now locked together and make one, that is why it is called direct.

Nick

But as I understand your still transferring power from the input to the output via the countershaft correct?

That's not the only diagram that calls it 5th gear.

 

[NIsaacs]

But as I understand your still transferring power from the input to the output via the countershaft correct?



That's not the only diagram that calls it 5th gear.

The only thing I can think of is, the diagram is of a 6th direct transmission when they talk about the 5th c/s and somehow the diagram is combined with the 6spd over?? When that transmission was used in medium duty trucks, it was a 6th direct only, no overdrive and was rated 650 ft lbs, it also had a 1. 5" input shaft.



Notice in the diagram, there is no 5th gear on the mainshaft. I really can't explain why they call that drive gear a 5th. That gear in all manual trannys is only to drive the counter shaft. When they change a transmission from a direct drive to an overdrive, they only change the input shaft drive gear combo and the counter shaft drive gear. The rest stays the same.



Nick

 

[RonD]

If your going to use the truck as you said for hauling and towing just change the oil when required, with that sort of use it will be between 5000 and 7500 miles, don't even think about extending beyond the service light more than 500 miles, it isn't worth it, the Dealer can tell, your warranty is in jeopardy, oil changes are cheap, engines are expensive

 

[JHumphries]

I think you guys are forgetting that the input shaft and main shaft are two separate pieces. The input shaft has the spline section for the clutch disc and the counter shaft drive gear. The main shaft starts at this point with the 5th/6th synchronizer section and continues on thru the gears to the output. Looking at this, when the shift fork moves the collar forward to 5th gear, it connects the input shaft to the main shaft making it a "direct" drive. Yes, the countershaft spins, but no power is routed through it as there is not a return path to the main shaft.

 

[AH64ID]

Looking at this, when the shift fork moves the collar forward to 5th gear, it connects the input shaft to the main shaft making it a "direct" drive. Yes, the countershaft spins, but no power is routed through it as there is not a return path to the main shaft.

Well don't I feel like a .....

I always looked at it and saw the 5th gear on the countershaft and presumed that's how it got direct, but you are correct it does tie the two together, but keeps the coutershaft spinning.

Thank's for breaking it down Barney style for me... .

My apologies Gonzo, I have been wrong about this.

 

[rscurtis]

The description in the drawing is misleading. The "5th C/S" should be called the "main drive gear", as all the power to the countershaft goes through this gear.