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Tow/haul or not tow/haul that is the question

Pulling my 22K fifth wheel in T/H, I usually run around 62 mph and on fairly flat terrain she will sit in 6th all day. 4.10 axle however may be the reason is shifts into 6th below 65 mph.
 
Blythkd1 said:
I figured the Cummins would be a torque monster at low rpm's but it's actually kinda opposite. It thrives on rpm's.
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Interesting observation. The C/C motor has lower rpm specs and a different cam, so I would have guessed the opposed in your observation.

I had the same rpm feeling about my 5.9, but not my 6.7’s. The 6.7’s, especially the 22, love low rpms. They don’t mind the rpms, but often don’t need them.

CdnHO said:
Pulling my 22K fifth wheel in T/H, I usually run around 62 mph and on fairly flat terrain she will sit in 6th all day. 4.10 axle however may be the reason is shifts into 6th below 65 mph.
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Also interesting, mainly because there isn’t anything noticeably different between the 3.42’s and 3.73’s I’ve had. 65 on the dot for both. The 22 does have much a better shift schedule thou, both TH and non-TH, but mostly down shifting.
 
Played around with TH and no-TH this morning. Accelerating as slow as I could, using CC above 20 to slowly increase 1 mph at a time, I came up with the following.

No-TH
1st to 2nd: 7 mph
2nd to 3rd: 16 mph
3rd TC Lock: 23 mph
3rd to 4th: 29 mph
4th to 5th: 35 mph
5th to 6th: 42 mph (surprised me, I hadn't recalled it was that slow... maybe I had my '18 with 3.42's on my mind)

TH
1st to 2nd: 7 mph
2nd TC Lock: 18 mph
2nd to 3rd: 26 mph
3rd to 4th: 37 mph
4th to 5th: 50 mph
5th to 6th: 65 mph
 
Ironic, I was playing with mine today just to see when it would hit 6th gear in TH mode. Mine was 62. Wouldn't shift up at 61. As soon as it hit 62, it went to 6th.
 
Blythkd1 said:
Ironic, I was playing with mine today just to see when it would hit 6th gear in TH mode. Mine was 62. Wouldn't shift up at 61. As soon as it hit 62, it went to 6th.
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With the 4.10’s and 235/80R17’s that a huge difference in TOS, so the C&C programming is certainly different.
 
AH64ID said:
With the 4.10’s and 235/80R17’s that a huge difference in TOS, so the C&C programming is certainly different.
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Yep. But without looking, I would have said my truck has 3.73's. In fact, I would have even bet on it. It was a year ago last December that I spec'd it out but 4.10 doesn't ring a bell for me.
 
Blythkd1 said:
Yep. But without looking, I would have said my truck has 3.73's. In fact, I would have even bet on it. It was a year ago last December that I spec'd it out but 4.10 doesn't ring a bell for me.
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Ah, for some reason I thought 4.10 was standard on C&C’s.

So with 3.73’s and 235/80R17 that puts the TOS the same as with my 285/60R20 or 275/70R18’s, so maybe it’s not that different.
 
I'm not 100% certain but at highway speed of about 70mph, pretty sure it's taching right around 1700.
 
Blythkd1 said:
I'm not 100% certain but at highway speed of about 70mph, pretty sure it's taching right around 1700.
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Sounds like 3.73.

It looks like 4.10 is standard on gas and max tow 3500 C&C’s. 3.73 is standard on the diesels without max tow.
 
AH64ID said:
Played around with TH and no-TH this morning. Accelerating as slow as I could, using CC above 20 to slowly increase 1 mph at a time, I came up with the following.

No-TH
1st to 2nd: 7 mph
2nd to 3rd: 16 mph
3rd TC Lock: 23 mph
3rd to 4th: 29 mph
4th to 5th: 35 mph
5th to 6th: 42 mph (surprised me, I hadn't recalled it was that slow... maybe I had my '18 with 3.42's on my mind)

TH
1st to 2nd: 7 mph
2nd TC Lock: 18 mph
2nd to 3rd: 26 mph
3rd to 4th: 37 mph
4th to 5th: 50 mph
5th to 6th: 65 mph
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Pulling my 22K fifth wheel on the way home yesterday on flat terrain. In T/H she was shifting into fifth at 55mph. Edited to correct the gear. Should have said 6th at 55.
 
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CdnHO said:
Pulling my 22K fifth wheel on the way home yesterday on flat terrain. In T/H she was shifting into fifth at 55mph.
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I’ll double check my notes when I get a minute. But pulling a trailer on flat terrain is still a lot more throttle than my empty truck on flat terrain.
 
I just found on my trip last week that my truck will do the aggressive downshifting when stopping even without being in TH mode. I had the exhaust brake on, didn't think to turn it off and see if that might make a difference.
 
Blythkd1 said:
I just found on my trip last week that my truck will do the aggressive downshifting when stopping even without being in TH mode. I had the exhaust brake on, didn't think to turn it off and see if that might make a difference.
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Yes, mine will do it too…. Sometimes. It only seems to do it with a trailer plugged into the bed, as is hasn’t happened with the last few bumper pull trailers.

I have a buddy with a ‘22 5500 and his does the same.
 
Yes, I should have mentioned, I was towing my 5th wheel. Funny thing is, sometimes it would trigger the aggressive downshift sequence and sometimes it wouldn't.
 
AH64ID said:
I’m assuming diesel on both, so if not sorry.

Whatever gear it puts itself in, they won’t hurt themselves. At 7500lbs I would personally use TH, which means you won’t be in 6th at 60.

The 6.7 is a very different beast than the VP 5.9. Between the added displacement, a variable geometry turbo, and HPCR the 6.7 is much better at low rpms. With an automatic transmission you can’t lug the 6.7, it won’t let you. The 2200 sweet spot on a VP 5.9 might be closer to 1800 on a 6.7. The 6.7 has adequate boost and programming to pull hard from ~1400-redline, and it will select the best gear to do that under most circumstances.

So use TH when you’re heavy, and let it’s do it’s think. You will rarely have to use the ERS to lock out gears, and when you do it’s usually due to rolling hills or long steep slow hills.
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Few times you mentioned a trailer weight and using TH. I found it's not always the weight but trailer's profile as well, I towed a utility trailer which was heavier than my slide in Truck Camper and was getting worse MPG.
 
MEGA HO 3500 said:
Few times you mentioned a trailer weight and using TH. I found it's not always the weight but trailer's profile as well, I towed a utility trailer which was heavier than my slide in Truck Camper and was getting worse MPG.
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Yes, drag has a lot to do with it. That’s where the weight comes into play for me, even a 3500 lb TT doesn’t have enough drag (weight or profile) for TH IMO.

But it’s all personal preference, as I know some folks who use TH empty every drive.
 
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For the last 10,000 miles or so, i've been driving in/around town w/ engine brake and Tow/Haul both on, to help w/ braking. I turn tow/haul off on the highway unless I'm actively towing.
 
AH64ID said:
Yes, drag has a lot to do with it. That’s where the weight comes into play for me, even a 3500 lb TT doesn’t have enough drag (weight or profile) for TH IMO.

But it’s all personal preference, as I know some folks who use TH empty every drive.
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Tried TH empty but with the 4.10 axle it really throws ya forward on the downshifts. :eek:
 
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