laramie longhorn 3500HO

[RustyJC]

Rusty, does Dodge with the 68rfe, recommend that both overdrives (5th & 6th) be turned off when towing?

No, just stick it in tow/haul mode and let the computers manage the powertrain. If you think it's hunting, you can use the shift lever buttons to lock 6th out, but I've never had to.



I have no idea what 60 MPH would be in 4th - I've never had to run there.



Rusty

 

[orhusky]

Rusty, How mudh does that 5th wheel weigh and what MPG's are you getting pulling it?

 

[RustyJC]

16,000 GVWR. It's 102" wide and 13'2" tall, so it pushes quite a bit of wind as well. I've yet to scale the setup with the 2011 truck. Fuel economy is improving as I get more miles on it - it has just over 3,000 miles now. The last trip from Athens, TX back to Cypress, TX (NW of Houston) on I-45 and backroads, it got 10. 4 MPG - that's up from 9. 4 MPG the first time we towed with it at around 1,000 miles. The 10. 4 MPG is about the same as I would get with my previous 2002 HO/6-speed/4. 10 dually that was BOMBed as a mild towing rig up to 347 rear wheel horsepower/762 ft-lbs torque with an Edge EZ and Diesel Dynamics Stage 2 injectors.



Rusty

 

[RVTRKN]

No, just stick it in tow/haul mode and let the computers manage the powertrain. If you think it's hunting, you can use the shift lever buttons to lock 6th out, but I've never had to.



I have no idea what 60 MPH would be in 4th - I've never had to run there.



Rusty

So its not like the 47re, where your supposed to "not" run in overdrive when towing? Most overdrives are for fuel economy, and are not recommended while towing. On flat lands I would run overdrive, if I had an automatic, but when pulling grades, I would turn it off, regardless of the transmission decision to run in overdrive. The big difference with mine being the G56 is I have to make that decision, and I never run in 6th while climbing grades heavy, to keep the RPM's up, to help keep the EGT's down.

 

[RustyJC]

So its not like the 47re, where your supposed to "not" run in overdrive when towing?

Nope, that was probably because the overdrive in the 47RE was a weak (relative to the rest of the transmission) add-on to the TorqueFlite 727. I had one in my 1996 V-10 dually and ran with it locked out when towing as well.



In the Diesel supplement to the 2011 Owner's Manual, the use of Tow/Haul mode is addressed separately for the 68RFE and the AS68RC (Aisin). According to the manual, in both cases, Tow/Haul is to be used if gear hunting occurs when towing a trailer, hauling heavy loads, etc. , but the TCMs differ in how they handle 6th gear:



68RFE (page 68):



"In TOW/HAUL mode, fourth to fifth gear upshifts are delayed. Shifts into fifth and sixth gear are still allowed under steady cruise conditions. "



AS68RC (page 74):



"When operating in TOW/HAUL mode, sixth gear is disabled and 2-3 and 3-4 and 4-5 shift patterns are modified. Shifts into Overdrive (fifth gear) are allowed during steady cruise (for improved fuel economy). "



6th gear towing with the new HO and 4. 10s should be pretty stout with the 68RFE since 60 MPH puts the HO right on top of its 800 ft-lb torque peak at 1600 RPM.



Rusty

 

[rrl989]

Anyone know where the RPM's of 6. 7 with 4. 10's would be cruising empty at 70 mph in 6th OD ?

 

[RustyJC]

1612 x 70/60 = 1880 RPM in my dually. Depending on tire size, YMMV.



Rusty

 

[mpaulson]

I believe that 6th gear is only locked out with the Aisin transmission, my 68rfe can be in any gear I want it to be while in tow/haul mode. I rarely ever use 6th gear while towing my rv as I'm at 24,000# plus alot of wind drag with the canoes, kyaks and quads on the truck. Maybe if I had the 4. 10's it might make enougth of a difference that I could use 6th, but I doubt it. I do wish that I had the 4. 10's though since I push my truck quite hard and I am in the mountains almost every time I haul the r. v.

 

[zb39]

1612 x 70/60 = 1880 RPM in my dually. Depending on tire size,

That should give decent MPG at that speed.

 

[DEM123]

On the road this week, will take some Saturday and post 'em... .

 

[zb39]

Awesome!!!!!!!!! I am waiting to hear from dealer so I can order.

 

[d6c]

Anyone know where the RPM's of 6. 7 with 4. 10's would be cruising empty at 70 mph in 6th OD ?

2000 rpm's equals 72 mph..... all stock single tire... .

 

[DHuffman]

2000 rpm's equals 72 mph..... all stock single tire... .

That would be 69 MPH, since Dodge speedos read 3 MPH high in stock form...

my '05, '07, '08, and '11 all did. With my 255/80R17s my speedo is dead-on with GPS and road-side radars.



My truck turns 1800 RPM at 73 MPH.

 

[rrl989]

2000 rpm's equals 72 mph..... all stock single tire... .

Thanks for these RPM replies. With my old 47RE 4 spd OD w/ 3. 55's I get:

1500 RPM = 53 MPH & 2000 RPM = 70 MPH. It shows that the newest CTD's with 4. 10's & the 6 spd OD are pretty close as far as rpm/speed ?



Forget locking out my OD, I pretty much redline near 60 MPH in 3rd w/ the 3. 55's.

 

[mpaulson]

gear-speed calculator

Go to this website. You can change things like the tire sizes, gear ratios to ones like 4. 56 etc and all the mph will change accordingly. I downloaded it and saved it on my computer so that I would always have it. Check it out.



http://www.klenger.net/dodge/general-reference/gear-speed-calculator.xls

 

[zb39]

Nice site!!