Shift! **** You Shift!

RoyJ wrote:

swimmer_spe wrote:
But the lighter trailer, pulled faster would not have shifted up. It would have stayed in 5th.

Have you tried turning off cruise?

I almost never tow / haul with cruise on, because I want to know exactly what my throttle position is.

You may find with the cruise off, you are able to pull in 6th, by keeping the throttle position just under the point where it triggers a downshift. If there's a slight hill or headwind, as long as you hold your throttle steady, the truck would bleed off a bit of speed, and you may be still locked in 6th.

With cruise, depending on the programming algorithm, the slightest speed loss may cause the computer to over-compensate and grab 5th.

If you can't even get into 6th, try accelerating to say, 115, then back off the throttle to let it upshift, then maintain enough throttle to hold 110. If it can't, then you know your engine simply don't have the power at that rpm to do it. Could be a lighter trailer has higher wind drag.

I can, but for long drives, I prefer cruise on. I am thinking it is wind drag.

swimmer_spe wrote:
But the lighter trailer, pulled faster would not have shifted up. It would have stayed in 5th.

Have you tried turning off cruise?

I almost never tow / haul with cruise on, because I want to know exactly what my throttle position is.

You may find with the cruise off, you are able to pull in 6th, by keeping the throttle position just under the point where it triggers a downshift. If there's a slight hill or headwind, as long as you hold your throttle steady, the truck would bleed off a bit of speed, and you may be still locked in 6th.

With cruise, depending on the programming algorithm, the slightest speed loss may cause the computer to over-compensate and grab 5th.

If you can't even get into 6th, try accelerating to say, 115, then back off the throttle to let it upshift, then maintain enough throttle to hold 110. If it can't, then you know your engine simply don't have the power at that rpm to do it. Could be a lighter trailer has higher wind drag.

mkirsch wrote:

swimmer_spe wrote:
It is not that I am looking for a solution. It is i am looking for the cause.

I thought I pretty well explained it back on page 4, but I can't seem to find my reply.

You pulled the bigger trailer FASTER. Faster means more engine RPMs, meaning more power output from the engine. If you're talking about crossing that magic ~2000RPM threshold, it's a LOT of power.

With my old truck I could always tow the trailer better in OD at 75MPH, because the engine was turning about 2300 RPM vs. 1900 RPM at 65MPH. Just that 400RPM difference doubled the power output from the engine. At 65MPH, I had to lock out OD and run at 2800RPM to keep from hunting.

But the lighter trailer, pulled faster would not have shifted up. It would have stayed in 5th.

swimmer_spe wrote:
It is not that I am looking for a solution. It is i am looking for the cause.

I thought I pretty well explained it back on page 4, but I can't seem to find my reply.

You pulled the bigger trailer FASTER. Faster means more engine RPMs, meaning more power output from the engine. If you're talking about crossing that magic ~2000RPM threshold, it's a LOT of power.

With my old truck I could always tow the trailer better in OD at 75MPH, because the engine was turning about 2300 RPM vs. 1900 RPM at 65MPH. Just that 400RPM difference doubled the power output from the engine. At 65MPH, I had to lock out OD and run at 2800RPM to keep from hunting.

swimmer_spe wrote:


Yet no one has given me an explanation why it didn't do it with a heavier trailer.

The more and more I think about it, the more and more I think something is not working right, as apposed to my driving skill. The heavier trailer should have been more of an issue, but crossing Canada (4000km) it pulled like a dream. It would sit in 6th at 110 km/hr. Now, a lighter trailer, at 100km/hr it is hunting.

So, excuse me if I take issue with someone saying "just don't use the top gear".

Which is why, yes, until I get it checked out, I will tow in 5th. However, this does not mean I should.

I can't speak for Ford, but my Duramax doesn't even want to shift into 6th gear until I exceed 60 mph in tow/haul mode. Chevy's tuning for tow/haul mode moves the shift points higher in the rpm range, locks the torque converter earlier (2nd gear vs 4th) and delays downshifts.
You said you were towing the heavier trailer at 110kph... maybe just enough more rpms to allow the engine to make the torque needed to keep it all rolling down the road? Or fast enough to stay above the shift point? Really, we've beat this horse enough!

swimmer_spe wrote:

Thunderbolt wrote:

It doesn't matter if you are towing or not. You could be driving empty in the mountains and on steep inclines the same applies. The bottom line is if it is hunting for gears then select the lower gear and roll with it.

It is not that I am looking for a solution. It is i am looking for the cause.

The solution is to do what it takes for it to stop hunting. Whether that means slowing down or shifting down a gear, as long as it stops hunting, the transmission is saved.

My question is what is causing it. 12 pages later, I feel I know what is causing it and what my options are to stop it.

Allow me to simplify multiple posts that address the CAUSE of the "issue."
Not enough torque to maintain a certain gear ratio with the load applied. Period.

unless there's a problem which so far was not diagnosed and probably isn't a problem, that is the cause. Not sure why you feel it held a gear longer last year with a different trailer. Doesn't matter at this point. IMO, and I've driven recent models of all the big 3 half ton V8s, the 5.0 Fox motor is the hardest pulling of the 3. To the Hemi guys, I have not towed with a 8speed, just the 5 speed.

The cause is this: A 5 liter engine is a small engine and it needs to spin pretty high RPM to make power.

The higher an engine spins the more power it will make up to it's redline limit. Your little engine will shift down to make more power to pull a hill. It reaches what ever RPM the OEM sets and it will shift into a higher gear. It does not have enough power to pull that gear so it starts to lose speed. When it loses enough speed and RPM, it will down shift and the whole cycle will start over again.

About the only way to fix your truck is by locking the high gear out so it can't go into it. Or put a supercharger on the engine so it makes a lot more power at a lower RPM.

The first one is a lot cheaper.

Thunderbolt wrote:

It doesn't matter if you are towing or not. You could be driving empty in the mountains and on steep inclines the same applies. The bottom line is if it is hunting for gears then select the lower gear and roll with it.

It is not that I am looking for a solution. It is i am looking for the cause.

The solution is to do what it takes for it to stop hunting. Whether that means slowing down or shifting down a gear, as long as it stops hunting, the transmission is saved.

My question is what is causing it. 12 pages later, I feel I know what is causing it and what my options are to stop it.

[
It doesn't matter if you are towing or not. You could be driving empty in the mountains and on steep inclines the same applies. The bottom line is if it is hunting for gears then select the lower gear and roll with it.



quote=swimmer_spe]I seem to have to keep repeating myself. I would expect the heavier trailer that is less aerodynamic to cause issues. But it is the lighter, more aerodynamic trailer that is causing me issues.

That would be the same if towing an empty utility trailer causes more problems than a tri-axle boat trailer with a boat.

If you keep letting it hunt for the right gear then fuel savings will be the least of your worries. You will burn up the transmission. In all reality you will probably only have one maybe 2 mpg difference from 5th to 6th. It may actually be better in 5th.

swimmer_spe wrote:
I know how to lock 6th out. I just want to use 6th. It sounds like I shouldn't. ****!

The thing is, we are taking within 5km/hr difference. I would rather go 5km/hr slower and save fuel.