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Heavy Towing in 5th Gear (68RFE)

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Old 01-30-2018, 12:12 PM
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Heavy Towing in 5th Gear (68RFE)

I recently swapped the factory 17" wheels and 265/70/17 tires for a set of 18" wheels and 285/70/18 tires. This obviously resulted in drop in RPM at any given cruising speed, and unfortunately pulled me right out of the sweet spot for towing at 62-65mph, and now the truck lugs a little bit (below 1500RPM).

So, here is the stupid question for today: Is there any issue with "locking" it into 5th gear to bring the RPM up? My Mini-Maxx shows the torque converter apparently locks in 5th, so in my pea brain everything should be just fine? We are planning a pretty long road trip this summer and will be at (OK, maybe even slightly above ) rated capacity, and I am trying to decide if I need to look into a gear swap, or if I can just use the fancy buttons and ***** already present in the truck
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Old 01-30-2018, 04:48 PM
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That is where i Run Mine. Just spent 5 Months in the Canadian Rockies and it worked better for me. Truck looses too much speed before it decides to downshift from 6th otherwise. Rock Steady running 5th.
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Old 01-30-2018, 04:58 PM
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Towing in extreme headwinds I often lock in 5th on my 68RFE just to keep the EGT's reasonable, fuel burn is not nice though. When towing in the mountains I always manually shift down that way the engine is not lugging.
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Old 01-31-2018, 06:19 PM
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That’s the beauty of the newer autos, you have six gears and can lock in the gear that suits conditions like a manual. Run what you like.
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Old 02-02-2018, 01:07 AM
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I tow our 15k fiver in fifth gear about 90% of the time. I will occasionally shift to sixth on the flats with no wind. My deciding factor is EGTs. With 3.73's and the 68RFE, I turn about 1900 rpm's at 65 mph.
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Old 02-02-2018, 08:07 PM
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Originally Posted by BobTipton View Post
I tow our 15k fiver in fifth gear about 90% of the time. I will occasionally shift to sixth on the flats with no wind. My deciding factor is EGTs. With 3.73's and the 68RFE, I turn about 1900 rpm's at 65 mph.
That's right where mine is as well. I hitched up and went for a little test run this afternoon just for grins and to play with the "manual" transmission mode. Worked great!

As always, thanks for the feedback everyone!!
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Old 02-12-2018, 02:50 PM
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I tow 130000 lbs and always tow in 5th..I too have 18 inch tires...at 65-70 mph I am at usually 2000-2100.....been that way for the past 2 trucks. That is the sweet spot for it and it purrs up and down grades and never skips a beat....It takes a pretty steep grade or a really long grade for it to drop down a gear...
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Old 02-14-2018, 07:39 PM
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I keep reading about the weak,overdrive gear in the 68 RFE. Is that just sixth gear or also fifth ? Craig
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Old 02-14-2018, 07:48 PM
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My biggest issue is in 6th it hunts gears even on the littlest grades. I 5th it just purrs along......Your rpm's need to stay above 18-1900 to stay in your power band.... On flat ground in 6th mine drop to 13-1400...
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Old 02-14-2018, 08:20 PM
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I agree with keeping the RPMs up. My 03 really likes 2100 to 2200 . My 12 is waiting for me to return from Arizona so I can swap the beds on my trucks and then I will be able to drive it again but I'm glad to hear that the 6.7 likes higher rpm's too so I can avoid using sixth gear so much . Craig
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Old 02-14-2018, 08:47 PM
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Originally Posted by steelpony5555 View Post
I tow 130000 lbs and always tow in 5th..I too have 18 inch tires...at 65-70 mph I am at usually 2000-2100.....been that way for the past 2 trucks. That is the sweet spot for it and it purrs up and down grades and never skips a beat....It takes a pretty steep grade or a really long grade for it to drop down a gear...
Wow!! You tow a 130,000 trailer?? What's ya pulling? A jumbo jet?

I knew these trucks were better than any Ford, GM, or other truck manufacturer, but that exceeds any expectations I ever had!!!




Lol
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Old 03-24-2018, 10:02 PM
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See my signature, I'm towing in 5th gear all the time, no downshifting up to 6% grades. Have not done anything greater yet.

2150 to 2200 rpm at 64 mph. If your towing with big tall tires you've change your effective rear ratio to a higher number 4.10 could drop to 3.38 with 33" tires. You need to watch your EGT's if your set up like that. I'm doing less than 10mpg in 6th. 10.5 in 5th gear.

Head gaskets are not cheap.

Dave
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Old 04-03-2018, 09:40 PM
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Originally Posted by CoastalDav
See my signature, I'm towing in 5th gear all the time, no downshifting up to 6% grades. Have not done anything greater yet.

2150 to 2200 rpm at 64 mph. If your towing with big tall tires you've change your effective rear ratio to a higher number 4.10 could drop to 3.38 with 33" tires. You need to watch your EGT's if your set up like that. I'm doing less than 10mpg in 6th. 10.5 in 5th gear.

Head gaskets are not cheap.

Dave
What do head gaskets have to do with towing in 5th or 6th?
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Old 04-03-2018, 10:00 PM
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It was said that oversized tires were being used with the question. Oversized tires reduce the rear end ratio and increases the load on the engine by reducing the RPM’s at any given speed which increases Exhaust Gas Temps. Exceeding 13-1400 degrees continuously will result in head gasket failure.

Dave
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Old 04-11-2018, 08:18 AM
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Originally Posted by CoastalDav
It was said that oversized tires were being used with the question. Oversized tires reduce the rear end ratio and increases the load on the engine by reducing the RPM’s at any given speed which increases Exhaust Gas Temps. Exceeding 13-1400 degrees continuously will result in head gasket failure.

Dave
Which sensor do you measure EGT's? I have OBD fusion and read the gauges from my phone. There's several choices of PID's. Just wondering which is the right one.

Going by the sensor I chose, EGT's never get above 500 in any gear. I haven't looked at the numbers towing yet.
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