3,500 miles on my '20 2500 Diesel Crew-couple observations and a couple questions

[Highcountry]

I just hit 3,500 miles on my 2500 Crew, 4x4, Cummins. I've never owned a diesel before, but have been around a few. First and admission-I probably don't need a diesel, but I've wanted one a long time and I keep my trucks for many years so I went for it. This last weekend was my first chance to tow my boat, which is only about 4k pounds soaking wet loaded with gear. Nonetheless I put it in tow-haul, turned on the exhaust brake and flipped down the mirrors. I got about 14mpg in this mode while towing the boat compared to 21-a high of 23.6 mpg on the freeway doing 65 with very light throttle. These are hand calculated #'s

First observation-I've got a better understanding of the 68rfe's shift scheme after making it display current gear with the gear limiting feature. I just set it on 6 so I can see what's happening. I wish it would always just display.

Second observation- I don't think I like the auto exhaust brake as well as full. I was under the impression that Auto only activated when you apply the brakes. I found this to be mostly true, but I'm sure it came on a couple times, while just coasting downhill. Full brake seemed to jive with transmission downshifts better.

Third observation-I don't hate the mirrors in the normal position, but like them way better on the trailer position. I think they should offer a mirror that gives a similar view all the time.

Question 1- does this truck even need to be in tow haul for 4k pounds? I suspect not, but want to do what I can to protect it mechanically. My boat doesn't have trailer brakes, so I'll probably always run it that way, but just wondering.

Question 2- What are acceptable upper end temps for Trans, coolant and oil? I don't have any concerns, just wanting to know what's a normal range. It was 114 degrees one day and my oil was 203 and coolant 194 I believe.

Question 3- I've heard these engines don't need much break in. I think it runs a little better after giving it a workout, albeit a light workout. Will mileage increase, decrease or stay the same over time? My buddy swearys his 17 has gone down some. Just curious, I'm thrilled with it so far

Question 4- at what point is calibrating the tire size in the system necessary? If add 1" does it matter? I know tire size will effect shift points and speedo reading, I'm just not sure at what point it's an issue.

This truck is without a doubt the nicest I've ever driven, even though I'm still getting use to having an automatic transmission. So far so good

 

[duallyben]

Full exhaust brake is way better, that's my opinion.

No tow haul with a 4k trailer won't hurt anything. Biggest difference I find is the throttle is a little more hesitant without tow haul off the line, and full exhaust brake is more aggressive with tow haul.

4k lb trailer don't worry about Temps honestly you are not pushing the truck.

No official break in for the engine, the break in is for the rear diff. I have heard mpg gets a little better some say, but I can't verify that. It won't be astronomical

 

[Epsilon Plus]

I just hit 3,500 miles on my 2500 Crew, 4x4, Cummins. I've never owned a diesel before, but have been around a few. First and admission-I probably don't need a diesel, but I've wanted one a long time and I keep my trucks for many years so I went for it. This last weekend was my first chance to tow my boat, which is only about 4k pounds soaking wet loaded with gear. Nonetheless I put it in tow-haul, turned on the exhaust brake and flipped down the mirrors. I got about 14mpg in this mode while towing the boat compared to 21-a high of 23.6 mpg on the freeway doing 65 with very light throttle. These are hand calculated #'s

First observation-I've got a better understanding of the 68rfe's shift scheme after making it display current gear with the gear limiting feature. I just set it on 6 so I can see what's happening. I wish it would always just display.

Second observation- I don't think I like the auto exhaust brake as well as full. I was under the impression that Auto only activated when you apply the brakes. I found this to be mostly true, but I'm sure it came on a couple times, while just coasting downhill. Full brake seemed to jive with transmission downshifts better.

Third observation-I don't hate the mirrors in the normal position, but like them way better on the trailer position. I think they should offer a mirror that gives a similar view all the time.

Question 1- does this truck even need to be in tow haul for 4k pounds? I suspect not, but want to do what I can to protect it mechanically. My boat doesn't have trailer brakes, so I'll probably always run it that way, but just wondering.

Question 2- What are acceptable upper end temps for Trans, coolant and oil? I don't have any concerns, just wanting to know what's a normal range. It was 114 degrees one day and my oil was 203 and coolant 194 I believe.

Question 3- I've heard these engines don't need much break in. I think it runs a little better after giving it a workout, albeit a light workout. Will milage increase, decrease or stay the same over time? My buddy swearys his 17 has gone down some. Just curious, I'm thrilled with it so far

This truck is without a doubt the nicest I've ever driven, even though I'm still getting use to having an automatic transmission. So far so good

AlphaOBD software can force the current gear always on display and there's threads in this forum you'll find that describe how. The ISB Cummins doesn't even know you have 4,000lbs behind you. Might as well have a single medium russet potato in the bed. That's about how stressed the truck is with that load. If you want to not have to get as hard on service brakes tow/haul will downshift through the gears more, helping to really utilize the exhaust brake. Otherwise, you'll exhaust brake down to a certain RPM and then the EB will shut off and you'll just stay in 4th until you come to a stop, using only service brakes. With tow/haul you'll be dropping down from 4th, 3rd, 2nd on the EB. MPG will increase as the truck wears in (not just engine, trans, diffs...etc). You may see a decrease as regens happen or as fuel filters start to get dirty.

Welcome to the forum and the Cummins ISB.

 

[Nd79]

Full exhaust brake comes on after lifting off the throttle. I like it for stop and go traffic (combined with tow/haul) and can often use it to get me slowed down pretty well before using the service brakes to come to a complete stop. This is when towing my dump trailer, empty weight of 4,500lbs so close to what you are towing. I like using tow haul just for the shift points.

Auto Exhaust brake comes on when you hit the brakes or maintains your speed downhill, full EB can slow you down more than your established speed when going down hill. I hope I made that make sense but it's kinda hard to put into words. Example: you crest a hill at 45mph with auto EB and the truck will remain at 45mph downhill without any driver input on the throttle or brakes.

I always keep my mirrors up, as I just like how I can see out of them that way and am towing 95% of the time with the truck.

 

[duallyben]

I run full exhaust with tow haul with my 2021 5500 at 19k lbs on the truck and never notice it go under. Coming from a 2016 3500 srw with 6.7 and aisin (towing not hauling like my 5500) I noticed right away ram tighted their cruise to keep you a lot closer to you set speed. I will tow the same trailer come late fall, but so far that was one of two major gripes they fixed.

 

[Nd79]

I run full exhaust with tow haul with my 2021 5500 at 19k lbs on the truck and never notice it go under. Coming from a 2016 3500 srw with 6.7 and aisin (towing not hauling like my 5500) I noticed right away ram tighted their cruise to keep you a lot closer to you set speed. I will tow the same trailer come late fall, but so far that was one of two major gripes they fixed.

Yeah that makes sense. I was just saying without cruise control at all, auto will hold your downhill speed and full EB will slow you even more if the load or trailer is light enough. These trucks are so awesome to tow with!

I usually run full EB with tow haul and keep my foot barely resting on the throttle if I want to coast without the slowing effect of the EB.

 

[Highcountry]

Full exhaust brake comes on after lifting off the throttle. I like it for stop and go traffic (combined with tow/haul) and can often use it to get me slowed down pretty well before using the service brakes to come to a complete stop. This is when towing my dump trailer, empty weight of 4,500lbs so close to what you are towing. I like using tow haul just for the shift points.

Auto Exhaust brake comes on when you hit the brakes or maintains your speed downhill, full EB can slow you down more than your established speed when going down hill. I hope I made that make sense but it's kinda hard to put into words. Example: you crest a hill at 45mph with auto EB and the truck will remain at 45mph downhill without any driver input on the throttle or brakes.

I always keep my mirrors up, as I just like how I can see out of them that way and am towing 95% of the time with the truck.

The part where auto maintains your speed downhill was what I was feeling. I wasn't aware that it functioned that way, thanks

 

[Highcountry]

I left out one of the questions I meant to ask. I know there is a weeks worth of reading on tire sizing and selection. Mine isn't about fitment, but more about when to calibrate

Question 4- at what point is calibrating the tire size in the system necessary? If add 1" does it matter? I know tire size will effect shift points and speedo reading, I'm just not sure at what point it's an issue.

 

[Yeasty McFlaps]

I just hit 3,500 miles on my 2500 Crew, 4x4, Cummins. I've never owned a diesel before, but have been around a few. First and admission-I probably don't need a diesel, but I've wanted one a long time and I keep my trucks for many years so I went for it. This last weekend was my first chance to tow my boat, which is only about 4k pounds soaking wet loaded with gear. Nonetheless I put it in tow-haul, turned on the exhaust brake and flipped down the mirrors. I got about 14mpg in this mode while towing the boat compared to 21-a high of 23.6 mpg on the freeway doing 65 with very light throttle. These are hand calculated #'s

First observation-I've got a better understanding of the 68rfe's shift scheme after making it display current gear with the gear limiting feature. I just set it on 6 so I can see what's happening. I wish it would always just display.

Second observation- I don't think I like the auto exhaust brake as well as full. I was under the impression that Auto only activated when you apply the brakes. I found this to be mostly true, but I'm sure it came on a couple times, while just coasting downhill. Full brake seemed to jive with transmission downshifts better.

Third observation-I don't hate the mirrors in the normal position, but like them way better on the trailer position. I think they should offer a mirror that gives a similar view all the time.

Question 1- does this truck even need to be in tow haul for 4k pounds? I suspect not, but want to do what I can to protect it mechanically. My boat doesn't have trailer brakes, so I'll probably always run it that way, but just wondering.

No it doesn't. On hills you shouldn't be in cruise control.

Question 2- What are acceptable upper end temps for Trans, coolant and oil? I don't have any concerns, just wanting to know what's a normal range. It was 114 degrees one day and my oil was 203 and coolant 194 I believe.

Upper is like 260? Super high. Not sure on the trans

Question 3- I've heard these engines don't need much break in. I think it runs a little better after giving it a workout, albeit a light workout. Will mileage increase, decrease or stay the same over time? My buddy swearys his 17 has gone down some. Just curious, I'm thrilled with it so far


MPG's should improve. A good break in is heavy towing during the first 6000 miles.

Question 4- at what point is calibrating the tire size in the system necessary? If add 1" does it matter? I know tire size will effect shift points and speedo reading, I'm just not sure at what point it's an issue.

Not essential for the mechanics of the truck. It's not going to hurt anything by not calibrating. It just won't be accurate with regard to speed and MPG's and total mileage

This truck is without a doubt the nicest I've ever driven, even though I'm still getting use to having an automatic transmission. So far so good

 

[MEGA HO]

I've had a TT which was about 4500# loaded. Did t use the TH mode