Towing in Overdrive

[AHarris]

When pulling heavy loads, do most of you just keep it in 6th or drop it down to 5th?



With my truck, I've noticed that towing my 9,000# camper seems to work a little better in 5th versus 6th gear. The transmission doesn't constantly down and up-shift on hills and the engine feels like it's not working as hard. Running 70mph, still only turning about 2,300 rpm. Fuel mileage between towing and 5th versus 6th seems about the same.

 

[RustyJC]

Towing our 16K GVWR 5th wheel, as a general rule I engage Tow/Haul and let the computer decide. If we're in rolling hills or some other terrain where the transmission starts hunting constantly between 5th and 6th, I'd downshift it to 5th, but otherwise I let the computers run the truck. Bear in mind that my truck has 4. 10 gears, so 6th is more useable for towing than 3. 73s or 3. 42s might be.



Rusty

 

[AHarris]

My truck has 3. 73s which explains why I get some hunting between 5th and 6th on hills.

 

[Slow Six]

I tow trailers that are in the 19000 to 21000 lb. range. I put it in Tow/Haul, turn on the exhaust brake, get up to cruising speed, set the cruise and enjoy the ride. For the most part the truck does things very well. I like to stay below the 2000 RPM as much as possible for cruising.

 

[Jim W]

I have an 11. 5K, 5er that I pull with the truck in my signature below. This is a 4X4 with 3:73 gears with the 6 sped auto; also your tire size will also determine what RPM your engine is turning. I am running the stock size tires that came with the truck, LT265/70R/17E. I do engage the Tow/Haul mode and let the computer determine the shift points most of the time. When I am towing on the highway on flat land I will tow in 6th gear doing around 1600 RPMs' between 60 to 65 MPH.

I will drop to 5th gear in the mountains but this is because I am trying to keep the egt's under 1000F when towing up hill. I will stay in that gear going downhill also since it is not wise to up-shift or down-shift when going downhill with a load. Another thing that I do is lock out 5 and 6 gear in town when the speed limit is under 45 MPH trying to keep the RPM's between the 1,400 and 1,900 range.

Jim W.

 

[Hoefler]

On these trucks with the 6. 7, 5th & 6th are overdrive. I tow our 40' fifthwheel in 6th all the time.

 

[AHarris]

I'm still freaked out from the old days when I had a 1990 Ford Ranger and toasted the auto transmission by towing a U-haul in overdrive across the country. Ever since then, I've always been careful not to tow in overdrive. Of course our 68RFE is a whole different animal so it doesn't look like I need to be as careful.



With my 3. 73 gears and stock tires, probably best to tow in 5th on hilly terrain to minimize gear hunting and EGT, and just leave it alone on the flats.

 

[Hoefler]

With the travel trailer you have listed in your signature, I doubt you will have any problem towing in 6th. It the transmission hunts, take it down a gear, if it doesn't, run with it. My 08 had 3. 73's in it, and it would pull my 40' 5ver with out any issues.

 

[AHarris]

On anything more than a small to moderate grade, I start getting a little gear hunting. Gear hunting is much more evident when I'm using cruise. If I turn cruise off (normally tow about 67-70 on freeway) and go easy on the foot, I can keep it from downshifting without losing much speed.



Cruise in hilly terrain seems to work the engine and transmission a little more. I'm sure when it's trying to take a long grade in 6th with the cruise on, the EGTs soar.

 

[RonD]

I leave mine in 6th, when the up ship, down shift is a issue, I leave it in 5th, but that isn't often

 

[EricBu12]

Aharis,

I have 15K 5th wheel. . I have the stock diameter but 19. 5" rims. . (225/70 R-19. 5") . . 14 ply "G". . the trailer has BF Goodrich Commercial T/A 16" "E" tires. this combo has reduced some of the drag with my unit. . The transmission likes to hunt when going up even a moderate hill. . I drop to 5th and use tow/Haul. . the TH mode reduces the chance for a downshift based on your throttle position. . In other words, you can push more. . this is true as well in 6th gear. . I try to pre-empt the shift by manually clicking down at 1600 rpm or so. . This puts the engine at a better RPM to pull the hill... When going downhill, I turn off The TH mode as it will try to downshift and slow down. Hope this helps.

 

[bob257]

I'm pretty new to all of this. I thought the tow/haul mode automatically kicked out the overdrive 5th and 6th gear? Usually I put it in tow/haul and put on the brake system and drive. Is there a better way?? I'm pulling a 40' 5er that's 11,900 dry. It seems to be okay so far.

 

[RustyJC]

I'm pretty new to all of this. I thought the tow/haul mode automatically kicked out the overdrive 5th and 6th gear?

Nope, not with the 68RFE in the pickups.



Like you, I typically just turn on the tow/haul and exhaust brake switches and let the computers manage the oily bits. It works quite well for me that way.



Rusty

 

[Cummins12V98]

Always have EB and TH on at all times. I tow my 27,000# combined in 6th on flat to small hills at 60 mph. When I get into 5 to 10 mph head winds I will hit 5th and on small hills. I use cruise set at 60 and manually adjust as needed before the computer can decide what to do, it keeps me doing something while driving and I do get better mileage that way. 3:42 gears.

 

[bob257]

If the tow/haul mode doesn't shut off overdrive, what exactly is it doing?

 

[RustyJC]

If the tow/haul mode doesn't shut off overdrive, what exactly is it doing?

Tow/haul raises the shift points on acceleration, increases the transmission line pressure for firmer shifts and less slippage, keeps the torque converter locked up as much as possible to lower transmission fluid temperature and provides a more aggressive downshift schedule to produce more exhaust braking effect when used in conjunction with the exhaust brake. If you'll notice, the harder you brake, the more aggressively the transmission will downshift when tow/haul is engaged.



If you want overdrive shut off (there are 2 of them, 5th and 6th gear), just use the +/- toggle on the end of the gear selector lever to select the highest gear you want to run in. For instance, if you want to lock out 6th gear, just toggle to display 5 on the EVIC screen.



Rusty

 

[bob257]

Thanks Rusty,

Another thing that I've noticed; when pulling up hill and the truck slows a bit, when I push the accelerator down it doesn't downshift like I've had other vehecles do. Is this normal? If I wanted more pull in that situation would it be better to let off the accelerator?

 

[RustyJC]

By not downshifting, the computers are trying to pull the hill in the current gear with the torque converter locked up - they're taking maximum advantage of the engine's torque curve if there's some torque rise available as the engine speed drops. When engine speed drops enough, it will downshift on its own. If you want to manually downshift, you can use the toggle switch to drop it a gear.



Rusty

 

[HBarlow]

bob257,

You may have read or heard comments about the C&C version truck with the Aisin transmission. The earlier models like my '08 and, I assume, the '09, did lock out OD6th when in Tow/Haul mode. I understand the Gen IV trucks now have the toggle shifter on the steering wheel like the pickups and they may not lock out OD6th any longer. I don't know.

 

[AHarris]

To me the truck just seems happier in 5th gear when driving through hilly country with the trailer in tow. I just lock 6th out using the +/- switch on the shifter. Mileage and transmission temps are the same either way.