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Gear Limit Switches not 100%?

Will_T

Will_T

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I have noticed on this long trip towing that once in a while the gear limit + and - paddles do not work. Press one or the other and nothing changes. It is a small percentage of the time, surely less than 5%. Has anyone else seen this? Or is there maybe some situations where it won't change the gear limit for some valid reason? So far it has always eventually come back and then worked as expected until the next time.
I find myself using it quite a bit as when towing at highway speeds the truck often wants to stay in 6th gear longer than it should. So I limit out 6th when approaching a hill or when the cruising rpm gets down below 1300 or so. But here in the west we do have lots of straight flat or slightly downhill highway that 6th gear seems to be fine for, even when towing. So I use the gear limit paddles quite a bit.
 
Have never seen that issue on mine.

I'm going to be locking out 6th more often on stretches with strong headwinds or inclines that cause it to shuttle to 5th and back to see what effect it has on mileage. We have a trip coming up Sunday so I'll try to report back a week after that.
 
Are you in 6th under load switching down to 5th? I notice under load in some conditions it won’t downshift, but let off the pedal and it will complete the shift.
 
It really depends on conditions, but it will generally downshift under load without having to lift. It acts very similar whether in TH mode or not, but obviously more aggressive and less pedal is required for it to drop gears in TH.
 
Thanks! I was not as clear as I should have been in the original post. It is not that it is showing the number in the display changing but not downshifting. Sometimes when I press the minus paddle, nothing happens on the display. Of course it does not shift either. For example if it is in 6th and I press minus, most of the time the display now shows a 5 where it should. Press it again, and it will show a 4 and it downshifts accordingly each time. But once in a while pressing the minus paddle, even several times, does not change the number in the display and no shift takes place. It is as if the paddle is not working. Eventually after a few minutes, it will work fine again. Being so rare and intermittent, so not being able to reproduce on demand, I was just wondering if anyone else had seen the same.
 
Have not seen this issue with mine not yet anyways as I only got 10,000kms on my truck, about half of which towing a light TT.
What I noticed is when I stay in 6th and I push TH button, it will continue to stay in 6th until there is time it needs to downshift. Once it downshifts, like when coming up the incline, it will not shift back to 6th even if going downhill.
I also noticed the fuel mileage in 6th and 5th are the same according to a lie-o-meter, but then we don't have the insane speed limits here like you guys have South of the border. Most of the highways in AB are 100kmh (62mph), few are 110 (68) and there's one I know in BC that is 120 (75) and even then I'm trying to stay at around 65mph as I'm not in a rush to get anywhere 10-15min earlier and a fuel consumption is noticeably better. Plus I'm married to a whining person Who doesn't like speed, even if it's posted speed limit, lol.
 
MEGA HO 3500 said:
What I noticed is when I stay in 6th and I push TH button, it will continue to stay in 6th until there is time it needs to downshift. Once it downshifts, like when coming up the incline, it will not shift back to 6th even if going downhill.
Click to expand...
Mine does the same when I have cruise control on. Mine also uses downshifts more than I expected to maintain downhill speed. I have the exhaust brake on. But even then, depending on speed the truck will sometimes down shift to 4th, or even 3rd going downhill when I am thinking the exhaust brake would be sufficient.

MEGA HO 3500 said:
I also noticed the fuel mileage in 6th and 5th are the same according to a lie-o-meter,
Click to expand...

At 65mph, I looked at that and the difference between 5th and 6th was always almost nothing. I also compared that meter to my manual calculations on this trip of about 1,500 miles and they were always real close. Always within a couple 10ths of each other. So mine seems to be fairly accurate. Towing mpg ranged from 9.5 to 11 mpg. Not towing, the two compare well also within a couple of 10ths. About 19 to 19.5 mpg.
 
MEGA HO 3500 said:
Have not seen this issue with mine not yet anyways as I only got 10,000kms on my truck, about half of which towing a light TT.
What I noticed is when I stay in 6th and I push TH button, it will continue to stay in 6th until there is time it needs to downshift. Once it downshifts, like when coming up the incline, it will not shift back to 6th even if going downhill.
I also noticed the fuel mileage in 6th and 5th are the same according to a lie-o-meter, but then we don't have the insane speed limits here like you guys have South of the border. Most of the highways in AB are 100kmh (62mph), few are 110 (68) and there's one I know in BC that is 120 (75) and even then I'm trying to stay at around 65mph as I'm not in a rush to get anywhere 10-15min earlier and a fuel consumption is noticeably better. Plus I'm married to a whining person Who doesn't like speed, even if it's posted speed limit, lol.
Click to expand...

Running in TH you're not going to get it to hook 6th gear unless you're going over 65. As I recall, 67 seemed to be the magic number.
 
Brutal_HO said:
Running in TH you're not going to get it to hook 6th gear unless you're going over 65. As I recall, 67 seemed to be the magic number.
Click to expand...
Maybe I am misunderstanding what you are saying. But I had TH on my entire trip and I often locked out 6th because my truck wanted to run in 6th even at speeds much slower than that. RPMs were down around 1100 so I locked out 6th to get them up some and also noticed that dropped the EGT1 quite a bit also. When I noticed it wanting to stay in 5th or even lower was on the downhills. I thought maybe having the exhaust brake in auto mode had something to do with that? The EB was working but it was also staying in a lower gear or downshifting to a lower gear.
 
Will_T said:
Maybe I am misunderstanding what you are saying. But I had TH on my entire trip and I often locked out 6th because my truck wanted to run in 6th even at speeds much slower than that. RPMs were down around 1100 so I locked out 6th to get them up some and also noticed that dropped the EGT1 quite a bit also.
Click to expand...

Under load?

I also have an HO...
 
Brutal_HO said:
Under load?

I also have an HO...
Click to expand...
Ha. Typing at the same time. No, when I noticed it I would not say it was under load, but running on long flat stretches. (Although this being my first diesel and only towing about 8,000 lbs of trailer, I am not sure it is really under much load even going uphill!) I still am not used to the power this truck pulls with. I don't fully understand the discussion of what the best rpms are to run like that but have read that it is better to run at say 1800 rpms rather than 1100 say. I did notice that the higher rpms gave lower EG temps and lower coolant temps which is contrary to what I saw with my old V-10.
 
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