The 6.4 HD Hemi Thread

sandawilliams · Feb 8, 2017

U&A said:
I agree. The 3.72 is the downfall of my truck. I will do this eventually but with a $2000 + bill i am going to have to hold off untill next year atleast. Kitchen remodeling is becomming a big bill.

Kitchen remodeling is big bucks- especially if there is a lady involved.

U&A · Feb 24, 2017

KarL45 said:
In reply to rivers question on gear change, Yes, I did have my dealer re-gear my Ram at about the 11k mileage. I am very satisfied with the work as well as the change for the better on general drivabilty as well as towing. I would ask though, what is your intended use for the truck. Also, where do you plan on towing? Truly, knowing what I do now and having towed for over 25k of the 44k miles I have on the truck, can honestly say if towing near the max weight, and also using it pretty much as a dedicated tow vehicle, would honestly consider the 4.88 gearing if it was available. For everyday driving as well as towing, I feel the 4.56 is about as good as it gets with the 66RFE Trans. Mileage in town is about the same. Mileage on the hi way depends on the elevation. Here in the Rockies with most of the daily driving in the 4,5,6k and over elevations, it is better. Still with that low of gearing, the engine tacks out at 2200 rpm at 80 in 6th. That is just where the 6.4 is starting to get happy. Also, the MDS is now working as well as possible in the higher elevations.

are you saying you have 4.56's? and you are at 2200 RPM's at 80 mph?

I have 3.73 gears and at 80 mph I am right at 2000 RPM's.

only a 200 rpm difference gong from 3.73's to 4.56's?

KarL45 · Feb 25, 2017

That is correct. 2200 rpm at 80 mph. The torque converter is locked up at that rpm. Before the gear change the locked rpm was 1800 rpm at 80. That was also with 3.73 gearing. While I love the low rpms cruising, I sure wish FC would build an 8 speed to go behind the 6.4. The cruising rpm isn't the problem but the high gearing and large gaps in the 66RFE gearing sure takes away from the capability for towing without having to rev the engine into the 4's or higher whenever a bit more power is needed. Would bet, if the "total" engine rpms over a set trip distance could be counted (towing), would bet that with the 4.56 gearing that the total rpms would be significantly "lower". Now tow in the mid 2's and rarely ever have to get into the 4's unless climbing or a fast acceleration. I love the gears.

U&A · Feb 25, 2017

KarL45 said:
That is correct. 2200 rpm at 80 mph. The torque converter is locked up at that rpm. Before the gear change the locked rpm was 1800 rpm at 80. That was also with 3.73 gearing. While I love the low rpms cruising, I sure wish FC would build an 8 speed to go behind the 6.4. The cruising rpm isn't the problem but the high gearing and large gaps in the 66RFE gearing sure takes away from the capability for towing without having to rev the engine into the 4's or higher whenever a bit more power is needed. Would bet, if the "total" engine rpms over a set trip distance could be counted (towing), would bet that with the 4.56 gearing that the total rpms would be significantly "lower". Now tow in the mid 2's and rarely ever have to get into the 4's unless climbing or a fast acceleration. I love the gears.

Are you just going by how the tranny and engine sound when you are saying the converter is locked up?

KarL45 · Feb 25, 2017

You can definitely hear it as well as the tack will reflect the change. A light acceleration will unlock the converter also and still being in the same gear will increase the engine rpm's. Any real significant throttle will cause a down shift of gears. You can watch it on your tack and if you have the gear selector activated, which I usually do. For example, coming up my drive, approx. 5 to 6% grade, will stay locked up in 3rd but the last portion when the grade increases more still, will unlock and the rpm's will increase. Still indicating in 3rd gear though. Again, if I were to actually accell to any real degree, the trans would downshift. Before the gear change, 2nd and even possibly first gear would have been required for the climb. Basically, going from 3.73 to 4.56 will take away your top end gear (6th) and add it to the lower end. That is the effect that will be noticed. But that said, unless you are hauling or towing heavy, probably, other than just the overall driving performance change, it probably isn't something most would want to do.

yoda · Feb 25, 2017

I asked this on a previous thread but will ask again anyway. It has always been my understanding it is illegal for a dealer to change axle ratios on a vehicle. Reason being the vehicle was emission certified with the factory gears.
Does anyone know if this is technically true?

15BlueStreak · Feb 25, 2017

KarL45 said:
You can definitely hear it as well as the tack will reflect the change. A light acceleration will unlock the converter also and still being in the same gear will increase the engine rpm's. Any real significant throttle will cause a down shift of gears. You can watch it on your tack and if you have the gear selector activated, which I usually do. For example, coming up my drive, approx. 5 to 6% grade, will stay locked up in 3rd but the last portion when the grade increases more still, will unlock and the rpm's will increase. Still indicating in 3rd gear though. Again, if I were to actually accell to any real degree, the trans would downshift. Before the gear change, 2nd and even possibly first gear would have been required for the climb. Basically, going from 3.73 to 4.56 will take away your top end gear (6th) and add it to the lower end. That is the effect that will be noticed. But that said, unless you are hauling or towing heavy, probably, other than just the overall driving performance change, it probably isn't something most would want to do.

I have a tradesman and the gear indicator does not change dynamically which annoys me. You always have to hit the minus on shifter. Do the higher option trucks with the larger display change when the transmission shifts?

U&A · Feb 25, 2017

KarL45 said:
You can definitely hear it as well as the tack will reflect the change. A light acceleration will unlock the converter also and still being in the same gear will increase the engine rpm's. Any real significant throttle will cause a down shift of gears. You can watch it on your tack and if you have the gear selector activated, which I usually do. For example, coming up my drive, approx. 5 to 6% grade, will stay locked up in 3rd but the last portion when the grade increases more still, will unlock and the rpm's will increase. Still indicating in 3rd gear though. Again, if I were to actually accell to any real degree, the trans would downshift. Before the gear change, 2nd and even possibly first gear would have been required for the climb. Basically, going from 3.73 to 4.56 will take away your top end gear (6th) and add it to the lower end. That is the effect that will be noticed. But that said, unless you are hauling or towing heavy, probably, other than just the overall driving performance change, it probably isn't something most would want to do.

I compleatly understand how it works. Just was wondering what you were comming from.

So the way your explaning it, when im going 65 or 70 mph in 6th gear the torque converter is not locked....? I can say that it is without a doubt locked in my truck at that speed.

Im a little confused in your explination. The torque converter will lock in at any speed as long as the circumstances are right. Veriables like hills and acceleration are things that will unlock it, but there is no given RPM or speed that you need to be at for it to lock.

EDIT: I am by no means trying to argue or start a fight. We could completely be on the same page and just not know it yet.

I just do disagree that you need to be at a certain RPM for the converter to be locked .

1500ram12 · Feb 25, 2017

15BlueStreak said:
I have a tradesman and the gear indicator does not change dynamically which annoys me. You always have to hit the minus on shifter. Do the higher option trucks with the larger display change when the transmission shifts?

No. All it shows is the gear you selected

Sent from my SM-N920V using Tapatalk

15BlueStreak · Feb 25, 2017

1500ram12 said:
No. All it shows is the gear you selected

Sent from my SM-N920V using Tapatalk

It would be nice if they did show which gear it was in as it shifted. Like the Fords.

U&A · Feb 25, 2017

15BlueStreak said:
It would be nice if they did show which gear it was in as it shifted. Like the Fords.

I have lerned to read the rpms/sound and speed to figure what gear im in....i also count it all the time...just to watch fo changes.

1500ram12 · Feb 25, 2017

15BlueStreak said:
It would be nice if they did show which gear it was in as it shifted. Like the Fords.

I agree

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15BlueStreak · Feb 25, 2017

U&A said:
I have lerned to read the rpms/sound and speed to figure what gear im in....i also count it all the time...just to watch fo changes.

Yes I can usually tell also by rpm just a feature that would be nice is all. I test drove a 2017 f250 yesterday with the 6.2 and 3.73 gears. It drove nice. Nothing that really screamed buy me. Overall nice truck but the xl and even an xlt did not have little things that my 15 tradesman has and vice versa. I guess life is all about compromise. For the money you can still get a tradesman with a Cummins for same price as a Ford gasser. I like Fords and may be in one again but it seems the price just keeps going up.

smiley · Feb 25, 2017

15BlueStreak said:
Yes I can usually tell also by rpm just a feature that would be nice is all. I test drove a 2017 f250 yesterday with the 6.2 and 3.73 gears. It drove nice. Nothing that really screamed buy me. Overall nice truck but the xl and even an xlt did not have little things that my 15 tradesman has and vice versa. I guess life is all about compromise. For the money you can still get a tradesman with a Cummins for same price as a Ford gasser. I like Fords and may be in one again but it seems the price just keeps going up.

It costs more for less features and it not as enjoyable to drive. Sounds like you better stay with us!

reek · Feb 26, 2017

15BlueStreak said:
I have a tradesman and the gear indicator does not change dynamically which annoys me. You always have to hit the minus on shifter. Do the higher option trucks with the larger display change when the transmission shifts?

I have a big horn with the higher end display. if I use the little button on the shifter to go from "D" to "6" and disable MDS, it also show what gear I'm in as it shifts.

15BlueStreak · Feb 26, 2017

reek said:
I have a big horn with the higher end display. if I use the little button on the shifter to go from "D" to "6" and disable MDS, it also show what gear I'm in as it shifts.

So it will update dynamically without having to hit the minus button to show current gear as it downshifts and shifts up to next gear?

jbplumbing · Feb 26, 2017

stumbled on a clip of a 6.4 2500 with an exhaust, now im looking at some cat back options for my truck.. whos got what and why? looking at a flowmaster american thunder dual system. and i saw a mod a while back about something increasing the Y connector from the flat factory option.. any insight is appreciated.

LDBagger17 · Feb 26, 2017

I have a Magnaflow cat back, the one with dual exhaust tips. Seemed to be the best thing out there when I bought it. All stainless

reek · Feb 26, 2017

15BlueStreak said:
So it will update dynamically without having to hit the minus button to show current gear as it downshifts and shifts up to next gear?

yes, I set the top gear I want to shift to, lets say 5th. and it will count up 1, 2, 3, 4, 5 as it shifts on the display. and same when it down shifts. I always know what gear I'm in by the display as long as I use the button to get out of "D" and into "6" - mainly do it to disable MDS.

not my pic but here's what the display looks like. Right next to the PRND display if you switch down with the shifter button, it will display 6/6.

GsRAM · Feb 27, 2017

reek said:
yes, I set the top gear I want to shift to, lets say 5th. and it will count up 1, 2, 3, 4, 5 as it shifts on the display. and same when it down shifts. I always know what gear I'm in by the display as long as I use the button to get out of "D" and into "6" - mainly do it to disable MDS.

not my pic but here's what the display looks like. Right next to the PRND display if you switch down with the shifter button, it will display 6/6.

That's heat if it does, in my 17 tradesman if I select 5th gear manually, it shows 5th regardless of what gear I'm in

The 6.4 HD Hemi Thread

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