Cruise control and towing heavy - no no

[Cummins2014]

While I've yet to tow my current trailer up Daniel's, I would not use cruise if I did. I generally do not use cruise on reasonably steep grades.

I didn't think so. Thanks

 

[Wiredawg]

Friends, for the most part, I don't use CC on grades just because the throttle tends to hit harder in the transition from coming off a grade to starting another one. My new truck has a "Smart Exhaust Brake" that reads like it works better in maintaining speeds descending grades. I'm pretty conservative coming down steep grades, opting to downshift and going slower with the exhaust brake on my former '09 4500 C&C. Engine speeds would be right at 3,100 RPMS, getting max braking with the exhaust brake. With 33,400 lbs, I like going down steep grades about the same speed I go up. The Grapevine is a fine example with 45 mph on both sides of it. Anyway, I like the discussion and will check out the Smart Brake on our 5-week trip starting tomorrow. SnoKing, sounds like we'll be traveling where you are. We're hitting New Mexico, Arizona, California, Oregon, Washington, Idaho, Montana, Wyoming, and Colorado. Happy Trails, and be safe, Ron

 

[Wiredawg]

I could be a convert on using CC on grades. The Max Tow programming down shifts smoothly and doesn't apply a lot of throttle to keep up to speed. The smart brake feature is very cool.... you can't hardly tell it's being used. There's a lot of technology in play here. I'll be in touch. Ron

 

[dfb]

Have had a 15 with 3:42s and now a 17 with 4;10s., the 15 in 6th while towing on flat ground would hunt between 5 and 6... The 17 does not hunt.. using tow haul however keeps the aisins in 5 th....

 

[Cummins2014]

Have had a 15 with 3:42s and now a 17 with 4;10s., the 15 in 6th while towing on flat ground would hunt between 5 and 6... The 17 does not hunt.. using tow haul however keeps the aisins in 5 th....

Must have had a lot more weight then my 38' Montana Fifth Wheel, My 2014 3500 SRW Megacab 3500 will hold 6th all day on flat ground, and even some slight grades with the 3:42's and the 68rfe.

 

[SnoKing]

Must have had a lot more weight then my 38' Montana Fifth Wheel, My 2014 3500 SRW Megacab 3500 will hold 6th all day on flat ground, and even some slight grades with the 3:42's and the 68rfe.

At what speed?

 

[Cummins2014]

At what speed?

65

 

[SnoKing]

65

With the Aisin, 65 is when it will shift to 6th with 3.42 gears. RPM would be pretty low for towing. Like 1400-1425 RPM.

 

[kthaxton]

While my max trailer weight is only around 12k, on level and slight grades....6th works great.

 

[SnoKing]

While my max trailer weight is only around 12k, on level and slight grades....6th works great.

Again at what speed? My truck would tow fine in 6th at 70-80 MPH. At 80 I would be at the same 1750 RPMs that I tow in 5th at 60MPH.

 

[kthaxton]

It varies obviously, but usually between 65-70

 

[Cummins2014]

With the Aisin, 65 is when it will shift to 6th with 3.42 gears. RPM would be pretty low for towing. Like 1400-1425 RPM.

About the same with the 68, to be fair, I don't tow less then 65. Usually 65-70. If I do encounter gear hunting with slight grades, and some head wind , I will lock it in 5th, but with pretty flat roads it runs great in 6th, but I don't see much difference in mileage with 5th or 6th towing. When I go Montana I will usually leave it in 5th ,too much hill climbing ,wind etc.

 

[Cummins12V98]

Must have had a lot more weight then my 38' Montana Fifth Wheel, My 2014 3500 SRW Megacab 3500 will hold 6th all day on flat ground, and even some slight grades with the 3:42's and the 68rfe.

I towed plenty 28-29K combined with my 11 HO with 68RFE and 3.42's. It would downshift 6-5th on hills. I experimented and leaving it in 5th at 1,750 in 5th at 60-62 worked overall the best. THAT is how I knew 4.10's would be the best for me at my higher weights now.

 

[kthaxton]

I could have predicted towing with 4.10's would be much better at those heavier weights without that experience.
Just sayin...[emoji6]

 

[Cummins12V98]

I could have predicted towing with 4.10's would be much better at those heavier weights without that experience.
Just sayin...[emoji6]

Honestly to do it again WITH the AISIN I would most likely get the 3.42's even at my 33-35k combined weights.

 

[kthaxton]

....and you'd probably regret it after having 4.10's. Then the light bulb would go off: "Ahhh, now I understand what torque multiplication can do". [emoji6]

 

[SnoKing]

....and you'd probably regret it after having 4.10's. Then the light bulb would go off: "Ahhh, now I understand what torque multiplication can do". [emoji6]

Remember it is final gear ratio that counts. 5th gear with 3.42 is about the same final gear ration that the 4.10's have in 6th. When you go from .77 ratio to .63 you really take away the torque multiplication advantage of the 4.10. Low rear diff gear help in the lower gears, however the lower Aisin 1st and 2nd over come the disadvantage of the 3.42's.

0.77 x 3.42 = 2.6334
0.63 x 4.1 = 2.583

 

[Cummins2014]

Remember it is final gear ratio that counts. 5th gear with 3.42 is about the same final gear ration that the 4.10's have in 6th. When you go from .77 ratio to .63 you really take away the torque multiplication advantage of the 4.10. Low rear diff gear help in the lower gears, however the lower Aisin 1st and 2nd over come the disadvantage of the 3.42's.

0.77 x 3.42 = 2.6334
0.63 x 4.1 = 2.583

I keep hearing this first two gears on the Aisin, not having it, I don't see a disadvantage with the 68RFE . It seems to get the load moving pretty good.

 

[Cummins12V98]

....and you'd probably regret it after having 4.10's. Then the light bulb would go off: "Ahhh, now I understand what torque multiplication can do". [emoji6]

WHY, I have already explained I HAVE towed with 3.42's at 29K. ONLY issue was the 68RFE getting the load moving on grade. With the AISIN this is NOT a concern.

 

[Cummins12V98]

I keep hearing this first two gears on the Aisin, not having it, I don't see a disadvantage with the 68RFE . It seems to get the load moving pretty good.

Try

this 29K combo and report back starting on lets say a 3-4% grade.