V10 Shudder/vibration Climbing on Cruise Control

[A Traveler]

A steady speed isn't the issue. Excessive shifting is the issue. And we can control that better with our accelerator pedal.

Say WHAT? That’s ridiculous.

When climbing or descending a steep grade, you do not control what gear your automatic transmission is in with the accelerator! You do that with a finger on the shift pad or a hand on the shift lever, putting the transmission in the gear you want. In other words, you have to DRIVE it, not just sit there and hold the steering wheel.

The cruise control trying to keep a steady speed IS the issue as it often does that by auto-shifting and that is what we should be trying to reduce.

There’s should not be any “auto-shifting” when using cruse control on a grade. You should manually choose the gear you want as you get into the bottom of the grade. If you select the correct gear, there will not be ANY shifting as the cruise holds a nice, steady speed. That speed might be only 35 mph in third gear on a 7% grade, but use of the cruise like this makes sure you are not accidentally pressing the accelerator a little more and working the engine harder than necessary to maintain the speed set on the cruise.

I’ve driven our Freightliner XC-R/Cummins 400 HP ISL DP coach like this for 100,000+ miles, using cruise on even the steepest grades, including I-70 over the Rockies. Works perfectly.

 

[A Traveler]

""Using cruise control while driving through hilly terrain could cause the system to force multiple transmission shifts which could lead to overheating of the transmission fluid and premature component wear," said Stephen Leroux, automotive professor at Centennial College in Toronto."

See here.

-Don- Crescent City, CA

Within that article is what may be the stupidest thing I have ever read when it comes to a “how to drive” article. It is this:

”…Of course, you can turn off the cruise, and slow down, by hitting the brakes if you're going too fast – but you can only do that if you're paying attention…”

What form of total idiot drives anything and doesn’t pay attention to what he’s doing? Oh wait…I know. The idiots that think they can text and drive.

If this is truly how “dumbed down” driving has become for people today, I may have to consider whether it is time to come off the road and call it quits. Unbelievable.

 

[DonTom]

The idiots that think they can text and drive.

If it were up to me, I would make the penalty for texting while driving three times the penalty for drunk driving. IMO, it is three times as dangerous.

"Honk if you love Jesus, but text if you wish to meet him!"

-Don- Reno, NV

 

[DonTom]

Say WHAT? That’s ridiculous.

You never noticed you can prevent or force an automatic tranny to shift by using the accelerator pedal? For one example, step down fast going uphill it will downshift. Release the pedal a little if you don't want it to shift at all. Could even upshift on the same hill, at least for a short while. By getting the "feel" just right you can control the tranny shifting from the accelerator pedal. But if you have the CC on, it will decide for you. Often, we can do the better job.

-Don- Reno, NV

 

[Kirk]

But if you have the CC on, it will decide for you. Often, we can do the better job.

So probably you shouild just turn your cruise control off and leave it that way. You do what makes you happy and we will do as the design engineers intended.

 

[DonTom]

So probably you shouild just turn your cruise control off and leave it that way.

No need, because I normally drive an EV--even in the mountains as there is no shifting at all in EVs.

You do what makes you happy and we will do as the design engineers intended.

Are you sure of what they intended? Is there anything in your owner's manual on the subject? It's normally not a good idea to allow overdrive and cruise control in the mountains--too much auto-shifting, just as mentioned in my message number 23 here by "Stephen Leroux, automotive professor at Centennial College in Toronto." Probably a guy who teaches such engineers.

It's probably me who agrees with the engineers the most on this subject.

But I really have no issue with others who wish to do damage to their trannies. So do as you please with your own vehicles.

-Don- Reno, NV

 

[Kirk]

It's probably me who agrees with the engineers the most on this subject.

Kind of like the electric codes?

 

[DonTom]

Kind of like the electric codes?

Was there any I really disagreed with, or only questioned?

If somebody mentioned the neutral was always grounded in the beginning, I would have questioned a lot less.

-Don- Reno, NV

 

[A Traveler]

You never noticed you can prevent or force an automatic tranny to shift by using the accelerator pedal? For one example, step down fast going uphill it will downshift. Release the pedal a little if you don't want it to shift at all. Could even upshift on the same hill, at least for a short while. By getting the "feel" just right you can control the tranny shifting from the accelerator pedal. But if you have the CC on, it will decide for you. Often, we can do the better job.

Of course I have noticed that kind of behavior with the manipulation of the accelerator. My point is that’s not the correct way to control your transmission. Trying to hold a steady throttle position with the degree of surgical precision required to hold in a certain gear is not always possible. Hit a little bump, your foot moves slightly in response and bingo, you just shifted down to a gear you don’t want it be in.

My point here is that the correct way to put your transmission in the gear you want it to be in and hold it there is with the transmission control, not the accelerator.

I manually choose the right gear for the grade, then use the cruise control to be sure that the throttle position does not change and the transmission does not shift up or down as I climb the grade.

 

[DonTom]

My point here is that the correct way to put your transmission in the gear you want it to be in and hold it there is with the transmission control, not the accelerator.

I've done that one too many times in the dark and then needed a new tranny in my Y2K RV. Not sure how it got into reverse! That happened near Needles, CA. Now I hesitate to shift an auto-tranny while driving.

-Don- Fernley, NV (electric motorcycle ride)

 

[A Traveler]

I don’t know how to respond to that, Don. In well over a million miles of driving cars, trucks, busses, and diesel pusher RVs, in both day and night driving, I have never once had an issue placing a transmission into the gear I needed at the moment.

Modern vehicles won’t let you shift to reverse when moving forward, anyway.

 

[DonTom]

Modern vehicles won’t let you shift to reverse when moving forward, anyway.

I guess Y2K is not considered modern. What happened in my case, I was trying to figure out where a bad vibration was coming from while on the freeway. I thought I put it in neutral. But when I went to put it back in drive, I noticed it was in reverse. I then stopped in a place to see if my reverse would still work. It was just like being in neutral. I then got that and much more taken of care of as I lived in the RV for a week, in Needles, CA. The tranny than had 125K miles on it, so perhaps not much life left in it anyway. It was the Y2K RV listed below.

-Don- Carson City, NV

 

[Skipper]

Recently experienced a mild engine shudder/vibration on cruise control while climbing an overpass. Turned off cruise and it stopped. No shudder/vibration making climb without cruise. Runs normal on level road using cruise. Internet search suggest several things could be the cause. Anyone had/fixed this type occurrence?

Recently experienced a mild engine shudder/vibration on cruise control while climbing an overpass. Turned off cruise and it stopped. No shudder/vibration making climb without cruise. Runs normal on level road using cruise. Internet search suggest several things could be the cause. Anyone had/fixed this type occurrence?

UPDATE: First time out this year on 500 mile RT but had the same problem. Today, mechanic replaced ignition coil and spark plug on cylinder # 7 & 8. Problem solved! Hope this will help someone else.

 

[Skipper]

Recently experienced a mild engine shudder/vibration on cruise control while climbing an overpass. Turned off cruise and it stopped. No shudder/vibration making climb without cruise. Runs normal on level road using cruise. Internet search suggest several things could be the cause. Anyone had/fixed this type occurrence?

UPDATE: First time out this year on 500 mile RT but had the same problem. Today, mechanic replaced ignition coil and spark plug on cylinder # 7 & 8. Problem solved! Hope this will help someone else.

 

[Skipper]

Thought I had updated on this problem. Two new ignition coils and 2 spark plugs. Runs great!

 

[Skipper]

Thought I had updated on this problem. Two new ignition coils and 2 spark plugs. Runs great!

Guess I did.

 

[Ray-IN]

I don’t know how to respond to that, Don. In well over a million miles of driving cars, trucks, busses, and diesel pusher RVs, in both day and night driving, I have never once had an issue placing a transmission into the gear I needed at the moment.

Modern vehicles won’t let you shift to reverse when moving forward, anyway.

Yep, I accidentally pushed R when feeling for the mode button of my 1999 Allison at about 65mph. The Allison immediately whined, but nothing else. I pushed D, whining stopped, and everything returned to normal_ well, except my heart rate.

 

[Ray-IN]

UPDATE: First time out this year on 500 mile RT but had the same problem. Today, mechanic replaced ignition coil and spark plug on cylinder # 7 & 8. Problem solved! Hope this will help someone else.

Reasonable. When climbing a grade with CC engaged the engine is running at WOT continually until it reaches set speed.