Cruise control and towing heavy - no no

[SnoKing]

We have been traveling from Arizona back to Washington and found another cruise control issue. I run on cruise control a lot and have found that things go a bit screw on steep climbs on cruise control. I am running at 24,500 combined and the Aisin goes a little nuts on steep climbs not knowing what gear to be in. Take it off cruise and the gear hunting and stutter shifting goes away.

This only happens on real steep climbs, normal freeway hills are not an issue. I saw this on I-8 in heavy head winds going to San Diego and on state route 138 leaving I-15 headed up the grade before turning toward Palmdale.

Chris

 

[6V92TA]

its actually fairly normal on all sorts of vehicles when doing the hill climb... Cruise control can't anticipate hills so its always re acting after a loss of speed on a hill, whereas when you drive with your foot you tend to get on the pedal sooner.. a way around that problem if using cruise control is to wait until the vehicle loses enough speed to downshift and then manually lock yourself in that gear range until you get to the top of the grade

 

[Cummins12V98]

I have ZERO issues towing with cruise on. I always run TH and EB. I do drop a gear when I know the hill coming up will cause a downshift. But after the first gear drop the AISIN down and upshifts spot on. I have tried dropping a gear to get more speed but it did nothing.

I am wondering if this is a 3.42/4.10 issue???

 

[SnoKing]

I have ZERO issues towing with cruise on. I always run TH and EB. I do drop a gear when I know the hill coming up will cause a downshift. But after the first gear drop the AISIN down and upshifts spot on. I have tried dropping a gear to get more speed but it did nothing.

I am wondering if this is a 3.42/4.10 issue???

Could just be a programming issue with my truck. If I use the throttle myself, no issue. So program the cruise let my throttle use. SnoKing

 

[Cummins2014]

They may all have a programing issue, it does not take much of a grade for my truck to lose speed in sixth gear NOT towing, and shift to fifth, only to shift back to sixth ,and repeat itself. It cannot be a power issue. If I lock it in fifth then the cruise maintains whatever speed its set at.

As far as cruise on a steep grade, I want control of how fast ,what gear, etc. I may lock it in a gear, but no cruise on.

 

[kthaxton]

I'd say it's gear ratio. Everything is easier for the engine with lower gears....and as mentioned before, it's not just about engine RPM, lower ratios have more mechanical advantage.

 

[Cummins12V98]

They may all have a programing issue, it does not take much of a grade for my truck to lose speed in sixth gear NOT towing, and shift to fifth, only to shift back to sixth ,and repeat itself. It cannot be a power issue. If I lock it in fifth then the cruise maintains whatever speed its set at.

As far as cruise on a steep grade, I want control of how fast ,what gear, etc. I may lock it in a gear, but no cruise on.

I'm betting it would hold better if TH were on.

 

[TCDiesel]

The TCM update solved (NOV/FEB 17) this issue. My WITech II is not with me, otherwise I would post the Part #. In the picture You see the lighting bolts ,If the bolt is in the corner of the TCM it needs the Update..Don't trust what the SR tells You, FCA has New rules on Flashing, its essential(s) ONLY and the SR tablet will only show Recall updates and mandatory Updates. the truck needs to touch Dealer connect for current updates.

 

[SnoKing]

From a post in a year ago.

I had these done on my 2015 back in January(2017). I believe the third one and the last one fixed the hunting between gears on small hills.

TSB 08-82-16 ITBM
TSB 08-044-16 RFH RF Hub
TSB 21-004-16 TCM
TSB 05-013-15 ABS
TSB 08-017-17 BCM
TSB 18-037-16 PCM

This resolved the hunting between 5th and 4th on small hills. What I had on this trip twice is a different issue.

 

[dfb]

We have been traveling from Arizona back to Washington and found another cruise control issue. I run on cruise control a lot and have found that things go a bit screw on steep climbs on cruise control. I am running at 24,500 combined and the Aisin goes a little nuts on steep climbs not knowing what gear to be in. Take it off cruise and the gear hunting and stutter shifting goes away.

This only happens on real steep climbs, normal freeway hills are not an issue. I saw this on I-8 in heavy head winds going to San Diego and on state route 138 leaving I-15 headed up the grade before turning toward Palmdale.

Chris

I have the 4:10s.. if the cruise hunts i just hit the button up to 4th gear..

 

[SnoKing]

I have the 4:10s.. if the cruise hunts i just hit the button up to 4th gear..

In the fall of 2016 heading to Arizona with the new 16K 5th wheel with a combined weight of 24,500 lbs, I would get hunting between 5th and 4th gear traveling 60 MPH on slight grades. The TSB above were flashed before we went back North in the spring of 2017. I would then come to a small grade and the Aisin would shift to 4th if needed and hold 4th gear until I crested the grade.

The problem noted in this thread is different and occurred twice on this trip North when pulling up grades with strong head winds (first time on I-8 entering California) and the second time on a long 7-8 percent pull off I-15 on 138 headed to Palmdale. This a several mile long hard pull.

SnoKing

 

[6V92TA]

better off locking it down in a lower gear for those sort of climbs than having the transmission bear the brunt of all that weight.
even though my truck has 410's ( not an Aisin even though) I have found it does a better job and runs cooler with less boost pressure on those climbs even though the engine is running faster

 

[SnoKing]

better off locking it down in a lower gear for those sort of climbs than having the transmission bear the brunt of all that weight.
even though my truck has 410's ( not an Aisin even though) I have found it does a better job and runs cooler with less boost pressure on those climbs even though the engine is running faster

In both cases I just took it off cruise control and the issue went away.

 

[6V92TA]

Snoking, that's not what I was talking about. just because a heavily loaded truck will pull a hill in top gear doesn't mean its not easier on the drivetrain to downshift a gear range and let the engine do the work instead of putting more strain on the transmission. you might even burn less fuel. anytime you are in an overdrive range the transmission becomes a torque divider and all the load is on the transmission. the driveline pulsations are magnified inside the transmission when in overdrive. as you shift down in there is less load on the transmission guts and its easier on the engine too. exhaust temps go downboost pressure goes down while engine speed goes up into the happy spots and cooling system temps go down too.

I did some high mile experiments running in 5th instead of 6th pulling the fifth wheel and I can tell you I saw a reduction in temperatures with little to no difference in fuel economy. It is counterintuitive but it makes sense when you figure out why

 

[SnoKing]

Snoking, that's not what I was talking about. just because a heavily loaded truck will pull a hill in top gear doesn't mean its not easier on the drivetrain to downshift a gear range and let the engine do the work instead of putting more strain on the transmission. you might even burn less fuel. anytime you are in an overdrive range the transmission becomes a torque divider and all the load is on the transmission. the driveline pulsations are magnified inside the transmission when in overdrive. as you shift down in there is less load on the transmission guts and its easier on the engine too. exhaust temps go downboost pressure goes down while engine speed goes up into the happy spots and cooling system temps go down too.

I did some high mile experiments running in 5th instead of 6th pulling the fifth wheel and I can tell you I saw a reduction in temperatures with little to no difference in fuel economy. It is counterintuitive but it makes sense when you figure out why

FWIW, I never tow in 6th, as it will not shift to 6th in towhaul until 65 MPH, and I tow at 60. It will shift to 4th on normal grade and go from 1750 to around 2100 RPM. On harder pulls it will go to 3 and turn 2500-2600 RPM at around 55 MPH. The Aisin seems to know the correct gear 99 percent of the time. I do drive the gear selector on down hills to keep it at the speed I want on the exhaust brake.

 

[TCDiesel]

I know this does NOT sound logical, But CR do not always conform to logic, the intake Sensors do effect CC, the MAP is generally the worst, Clean them and see if any change.

 

[6V92TA]

Snoking, what gear ratio do you have in that truck?

 

[SnoKing]

Snoking, what gear ratio do you have in that truck?

As noted in sig line, it is a 2015 SRW! Only one ratio available!

 

[6V92TA]

I'm not a mind reader nor can I guess what particular ratio FCA used in any given year. but anyway it sounds like you bought the wrong setup for such a heavy trailer..

 

[SnoKing]

I'm not a mind reader nor can I guess what particular ratio FCA used in any given year. but anyway it sounds like you bought the wrong setup for such a heavy trailer..

The latest gen SRW trucks only come with 3.42 gears. My truck is within RAM towing guide lines. It tows our 16K 5th wheel just fine. What this thread is about to two times in 43K of use the Cruise control would not function correctly on steep climbs.

The ability to cruise at 80 MPH at 1750 RPMs and get 18 MPG is a big plus. Combine that with the Aisin's low first and second gears for getting 24,500 lbs moving front a stop, and having 5th gear while towing turning 1750 RPM at 60 MPH it is the best of two worlds. I would not want any other gear ratio.