Getting ready to sell my 06 mega cab 5.9 for a quad cab 6.7 but unsure about the tranny to get. I had a 05 cummins with a stick and LOVED IT then my mega cab now is a 4 speed auto. I like it to but NOT like the stick. I like to change gears and i would like alot information about how the new 6 speeds autos work. You guys like them or not. Is the 6 speed sticks the same as they use to be or is there change in them also. Please help me decide. I dont pull alot if i do its only a 14,000 dump trailer maybe 5 or 6 times out of the year. Thanks alot.

 

which one will get the better fuel mileage also.

 

The 6spd. automatic actually has two overdrive gears to it. The manual has but one. So your fuel economy will probably be better with the automatic. A bonus for the automatic, it can be shifted like a manual with a switch on the shift lever. Also if you are looking for the most fuel economy stay with the standard 3.73 gear ratio instead of the 4.10 set. You said you won't be towing very often so it makes sense to get the 3.73's.

I sell Dodge trucks for a living so if you have any questions I'll try to help!!!

 

Ive owned manuals every since I started driving but I love my new 6 speed auto.

 

I've never cared to own an automatic, but I test drove that new 6 speed auto and really liked it. Nice positive shifts, the push button thing lets you have full control when you want, and it seems to work well with the exhaust brake feature.

The new auto was turning lower RPM w/4.10's than my truck with the NV5600 and 3.73's.

If I decide to replace my truck it will have the auto.

 

you should look it to the power ratings the manual is a 610ft/lb and the 68rfe is 650ft/lbs, so if that makes the decision for you, there ya go! the new 68rfe trans is a pretty EDIT tranny though, i personally thought i would never own a auto behind a cummins or any diesel, but this tranny has made me a believer.

 

[QUOTE=Gottlos;1499948]The 6spd. automatic actually has two overdrive gears to it. The manual has but one. So your fuel economy will probably be better with the automatic.




I wouldn't count on that. It's only the final ratio that counts in the discussion about RPM vs mileage. It's the 6th gear ratio on the highway, not the 5th gear ratio on the highway. It's not how many overdrives it has. And the automatic, no matter how good it is, will not be as efficient as a manual in top gear on the road.
The most important decisions will simply be wether you want an auto or a stick, if you want the extra power offered with the auto, and if you trust the new auto.

The most efficient drivetrain would not have an overdrive. It would have a straight through 6th gear and a higher differential gear. This would, in effect, make the tranny just a straight shaft in top gear, like the old 3 and 4 speed trannys. Instead of running gear sets and a lay shaft, that rob power, to get the (magic) 6th gear OD.

Wetspirit

 

[QUOTE=Wetspirit;1501212]Well the theroy would be correct if there was not the lock up TC in all moderen auto trans. This makes the power transfer the same as haveing a standard clutch in there. Where you gain your MPG with a stick is in the city driveing where the TC would be slipping. AS far as I can tell the new 6AT should have better highway MPG due to the higher 6th gear ratio.
AS far as driveing I still hate autos and so I ordered mine with a stick. I did drive the auto 6.7l before I ordered the stick, which they did not have so I hope that I like it. The auto was nice but not worth the $2000 price tag.
Hope this helps

 

Blue6.7,

The automatic is less efficient because it uses oil pressure to hold the clutches, the bands and the lockup converter. All the time it is running an oil pump and maintaining oil pressure, circulating fluid. The lockup converter is an important part of any modern automatic, but they still have the hydraulic system and they are not always locked up. All OD transmissions use a set of gears to give the OD ratio. Automatic or manual. Each gear set costs power. A straight through gearbox is more efficient.

My response to Gottlos was about the top gears. Not about city driving.

You can't just keep gearing higher and higher and expect to get better and better mileage. Matching the ratio to the engine and intended use is what counts. If it was simply a matter of gearing higher for better mileage then the gearing would be such that the engine was running about 500 RPM at 80 MPH and we'd be getting 40 MPG. There is a sensible limit to it. Not a direct ratio between higher gearing and mileage. Also, driveability goes down as the ratio goes up past a certain point. The engine starts lugging, is inefficient, and unresponsive.

To everyone who simply says all you have to do is raise the ratio and the mileage will go up by that or a similar amount, I simply ask have you tried it and why haven't all the worlds auto manufacturers been able to figure out such a simple and obvious solution? Just gear all new cars so the engine is running at about 200 RPM on the highway and the worlds oil crisis will be over. It will help if you are geared too low, but not if you are already geared too high.

Wetspirit

 

When are you hooking it, Derrick ?


Greg