Need Advice: Towing I-70 westbound out of Denver

[DaveHess]

Hello Everyone! I have been gone for a very long time but have returned. Too long a story there....

I will be traversing I-70 West bound from Denver to Grand Junction the third week of October 2025. I have never pulled my camper nor driven anything west of the Rockies, so this is a brand-new experience. And I'm going to do this with my 2003 2500 pulling my 2023 Grand Design 320MKS fifth wheel. I am very worried about the pull out of Denver to the Eisenhower Tunnel and then the downside west of the tunnel. Being I have not exposed myself or my truck to this kind of pull, I am unsure how to manage the 48RE in an effort to keep trans temps down and keep myself moving. I know OD is not even in this conversation, but do I pull this lengthy grade in 3rd or take her down to 2nd and what will be my cue to take her 2nd. I know the converter is not going to lock so I am worried about trans heat. I also understand travel speed will be greatly reduced. How do I manage this? On the downhill side, seems everywhere I read, the haulers say take it down a gear. I have some experience driving semis (limited) and was taught to allow the truck to targeted speed I want, then use the brakes to take me 10 MPH below that speed, release the brakes and allow the truck to return to the previous speed and continue this process until off the grade. That truck had a Jake, my 2003 does not have an exhaust brake. My bride really wants to go this route, so I am looking for any tips, thoughts, training to make this segment of our trip successful.

Real quick on my setup. I'm sure somebody reading this has done the math in their head regarding my Reflection being pulled by a 2003 2500. I'm going to jump right to bottom line. I have scaled my pickup alone in full camping dress by itself and with my Reflection hooked up. The GCWR for a 2003 2500 with a Cummins, 48RE, Quad cab, LB is 20,000. We are at 20,800 pounds. If somebody cares, Ill post all the weights that get me there. I've been pulling this camper for two years now and she has performed the task admirably.

I'll look forward to hearing from you all!

 

[petersonj]

You sound like you have a good idea of what you are getting into. You understand the shortcomings of a stock 48RE transmission for heavy towing in the mountains.

Personally, I would not tow what you are going to tow in the mountains. There will be no margin of safety with your rig for the long downgrades should something go wrong. And..., after finishing the downgrade from the Eisenhower Tunnels, 10 miles later you will repeat with climbing and descending Vail Pass.

Something that rarely gets mentioned regarding towing in the mountains is that the air density is much lower when you begin descending grades that start out at 10,000 and 11,000 feet. This means there is less wind resistance holding your rig back when comparing starting a descent with the same load at 4,000 feet - a BIG difference. I lived in Leadville, CO for 12 years and I have been up and down those grades many, many times. I respect them.

You still have time to upgrade your transmission and to have the transmission be modified to lock up the torque converter in second gear. Then, you could install a PRXB PacBrake exhaust brake. This setup will keep your brakes cool and you will be ready for an emergency stop, if necessary. You will hardly be using the brakes on the downgrades. Your trip will almost be stress free - at least the driving part. You also will also easily ascend the grades in second gear locked up - no risk of overheating the transmission.

Two years ago I hauled several loads of pavers (combined weight of 21,000 lbs) over 5 mountain passes here in Oregon - a total of nine trips. Of course my transmission is a 6 speed manual and the engine is equipped with an exhaust brake. I would not have considered making those trips with a stock automatic transmission and no exhaust brake.

Just one opinion,

- John

 

[DaveHess]

Thank you for the response John. Something I neglected to mention was we are coming out of North Dakota. As I have researched our options of routes, it appears we have choices. However, I feel I am still in the dark as to what challenges await me. My sweetie may have to settle for those views instead of the ones on I-70. Our plans have us departing Bismarck and stopping for the night in Lusk, WY (She limits my behind the wheel time to 8 hours a day). One of my thoughts was to travel to Grand Junction, CO the second day by way of Casper, WY working my way across and down to Rifle, CO and on into Grand Junction. The third travel day we have a short day into Moab, UT, where we will spend two days. Our final destination is Flagstaff, AZ. Our trip home is going to be through NM and back up to Lusk on the east side of the Rockies. There is just this one day on our way south where I have to cross over the Rockies in some way. This one day is my concern.

I downloaded a wiring diagram at some time over the past 22 years with this pickup to install a "Mystery Switch" to lock-up the converter manually. I even procured all the parts I thought I'd need. Just never got up the nerve to install the switch. The transmission has always been one of my top wish list items to be rebuilt and modified. The pickup has 140,000 on her now and with the exception of the transducer/solenoid that goes out on the bottom of the valve body, the 48RE has been solid for me with servicing every 25,000 miles. And thank you, I do understand the transmissions limitations. Add that to the prohibitive cost of a 48RE rebuild/modification with converter and thus lies my dilemma. I know that day is coming, hopefully on my terms, but right now she's running like a bad dog.

Dave

 

[petersonj]

Traveling via Lusk, Wyoming through Casper and then down to Rifle, Colorado will definitely keep you out of the high mountain passes. That would be a good route for you. Less traffic as well.

- John

 

[Grumpy8811]

you can assume if the torque converter stays locked the transmission should not overheat on a climb. If no exhaust brake, you descend the grade in the one gear lower than you climbed it and just dont let it get away from you and you can always use a pull out if you need to..

it is the Interstate and not some side route with 10 or 12 % grades.
I would think you should be able to climb The Ike with no issues.. assuming the truck can climb anything else.
you can always stay behind a tractor trailer that is crawling up or down that grade
as well as pull over if need be...

 

[GAmes]

If I had an automatic I would be proactive and get a few upgrades. I think that compared to a breakdown far from home it would be pocket change. I never leave home without my exhaust brake.

 

[bigceltic]

The only thing I will add is that going up to the tunnel going west is really not bad at all. Much more of a strain coming Eastbound. Lower gear on the downhill into Silverthorne and lower speeds in the right lane. What you need to be aware of is the hill out of Denver (where 70 crosses 470) - it is very steep. My temps climb on that hill, but coming down the other side cools them right off again. For me the biggest challenge towing is actually Vail Pass coming Eastbound (I assume you are going to be coming back that way).

 

[endoscott]

Add an exhaust brake. One of the best things about these Cummins trucks is the exhause brake, esp on down hill grades towing heavy. I added one on previous truck (2003) and of course it's on the 2014 we have now. I wouldn't love towing our 5th wheel without it. Sure you can get by but who needs the extra stress?

 

[Jim W]

I towed with my current truck a 2008, 2500HD, 6.7L Cummins with the 68RFE pulling a 34RL Cedar Creek on I70 up and through the Eisenhower tunnel. We were going to MOAB UT.

Granted my truck was not a 5.9L Cummins with the 48RE, but you should be able to handle this route with one modification to your set up, I think. I would add an exhaust brake to your current engine.

I pulled in 5th gear and maintained the 55mph which is the speed limit on I70, when traversing the roadway up and over the continental divide if I remember correctly. I did watch my EGT's and Boost pressure as we went up the interstate in 5th gear. The truck was also in tow/haul mode and exhaust brake was on. On the decent I stayed in 5th gear (as the truckers say whatever gear you go up in that is the gear you go down in) the exhaust brake did most of the braking for me to maintain the 55 MPH speed limit. I did have to tap on the brake pedal a few times when the curve speed limit was lowered to 45 if I remember correctly. I mainly followed the semis up and down staying in the RH land for the most part with flashers on just like the semis do.

It was more stressful for my DW than me. She had no brake pedal to engage as we descended from the tunnel on I70 into UT.

Another item you will need is chains for your truck and trailer when traveling in OCT on I70 in CO. I believe the law now states from Sept1 till May 31. This was changed recently to state all passenger vehicles are required to have additional traction devices. You may want to ask the CO DMV to confirm this.

 

[bigceltic]

Another item you will need is chains for your truck and trailer when traveling in OCT on I70 in CO. I believe the law now states from Sept1 till May 31. This was changed recently to state all passenger vehicles are required to have additional traction devices. You may want to ask the CO DMV to confirm this.

Traction Law
During winter storms, or when conditions require, CDOT will implement the Passenger Vehicle Traction Law. CDOT can implement the Passenger Vehicle Traction and Chain Laws on any state highway. During a Traction Law, all motorists are required to have EITHER:

1. 4WD or AWD vehicle and 3/16” tread depth
2. Tires with a mud and snow designation (M+S icon) and 3/16” tread depth
3. Winter tires (mountain-snowflake icon) and 3/16” tread depth
4. Tires with an all-weather rating by the manufacturer and 3/16” tread depth
5. Chains or an approved alternative traction device

Passenger Vehicle Chain Law
During severe winter storms, CDOT will implement the Passenger Vehicle Chain Law. This is the final safety measure before the highway is closed.
When the Passenger Vehicle Chain Law is in effect, every vehicle must have chains or an approved alternative traction device.

I have a set of Auto Socks which are an approved alternative traction device. Although I don't drive on the HW when it is that bad...

 

[Grumpy8811]

I look at some of the responses on this thread, all of which require the investment of money and think to myself that climb over Eisenhower Pass is still just like any other portion of the Interstate System and was doable before exhaust brakes, 400 hp diesel engine's and multiple speed transmissions were commonplace and think I would just handle it like they did before those more modern things existed.. I would climb and descend more slowly and use pullouts if I encountered some sort of heat issue with the truck..

Eisenhower Pass is not all that difficult once you realize it is still just an Interstate highway which is generally the easiest safest highway any person can drive on and was designed to handle heavy truck traffic, who are far more performance limited than people towing a RV.. the thread starter will be fine if he uses his head, so nothing to worry about here.

 

[bigceltic]

I look at some of the responses on this thread, all of which require the investment of money and think to myself that climb over Eisenhower Pass is still just like any other portion of the Interstate System and was doable before exhaust brakes, 400 hp diesel engine's and multiple speed transmissions were commonplace and think I would just handle it like they did before those more modern things existed.. I would climb and descend more slowly and use pullouts if I encountered some sort of heat issue with the truck..

Eisenhower Pass is not all that difficult once you realize it is still just an Interstate highway which is generally the easiest safest highway any person can drive on and was designed to handle heavy truck traffic, who are far more performance limited than people towing a RV.. the thread starter will be fine if he uses his head, so nothing to worry about here.

You are correct. I towed I-70 both directions many times without an EB. Easier with, but totally doable without.

 

[petersonj]

I personally like a bigger margin of safety when it comes to towing on long downgrades - especially when towing at maximum weights or slightly higher, as in the OP's case. Also, kudos to the OP for knowing his rig and asking for advice regarding doing something that he has never experienced.

Who knows, maybe upon arrival at the tunnel, the tunnel is closed and traffic is being diverted over Loveland Pass. It happens occasionally. Now the margin of safety just got narrower. Oh, and you get to start the downgrade at just over 12,000 feet.

A couple of Loveland Pass photos:

- John

 

[DaveHess]

Thank you all for your advice and words of wisdom. Maybe Sag2 could jump in and clarify but I'm pretty sure in order to install an EB on my 2003.5, it would require a transmission VB upgrade to keep my converter locked up with the EB engaged. Otherwise, the EB is useless. This pickup still has its original brake pads and rotors. And the Pads are measuring out at between 5 and 6mm. Its time. I bought Wagner SD pads and Bosch Quiet Cast rotors. I'll do the brake job in a couple of weeks.

Just reiterate, I have two main concerns: 1) While climbing long grades in any other forward gear other than 3rd and OD, the converter is going to remain unlocked and create a lot of heat. Route 16A east of Rapid City, SD was the last hard pull I made with my current setup. It was in stop and go traffic with an ambient temperature around 95. In this situation, she ran between 2nd and 3rd gear, converter unlocked the entire time on 16A. I know there are different schools of thought on trans temps but the outgoing fluid temp to the coolers was around 230 to 240 and the fluid in the pan was hanging around 190. The ECT was a whole other deal. The ScanGuage II showed ECT at about 218 to 220. When I stopped at red lights, I'd put the truck in neutral. when I did this, the engine RPM would climb to about 1200 and the fan just howled. Other than the temps, the pickup pulled hard and didn't blink an eye. This was my first "hilly" pull with the Grand Design. We've done this pull many times over the past 22 years but all with GCW of 18,000 pounds or less. The only other climb that this pickup has been used with a camper was Bozeman Pass in Montana. That was at 18,000 pounds GCW. Not a single issue there. That is my only real experience pulling grades with a camper. We have been all over east of the Rockies with campers. Just not west. 2) My second concern was controlling the descent. My experience with a semi has been gear it down, pick a top speed you're comfortable with. When you hit that speed, use the brakes to scrub off about 10 mph, and let her roll back up to that speed again and repeat. If I climb to Eisenhower Tunnel in 2nd gear, what's 2nd going to be like going down the other side? I have no idea on this. Will it hold back 20,800 pounds enough to give the brakes a cooling cycle with my 10 mph scrub? I have this mental picture of watching the tach head rather quickly to the redline and have no alternative but the brakes.

This is where I was looking for advice. I am a retiree with a somewhat limited income that right now does not support transmission upgrades and the EB. That's a fact of life right now. I sincerely appreciate all the posts above and please keep them coming. Somebody out there in TDR-Land has done this with a truck and trailer configured like mine. How did you do it???

 

[Grumpy8811]

This is where I was looking for advice. I am a retiree with a somewhat limited income that right now does not support transmission upgrades and the EB. That's a fact of life right now. I sincerely appreciate all the posts above and please keep them coming. Somebody out there in TDR-Land has done this with a truck and trailer configured like mine. How did you do it???

I'm retired too... like you the money I have is all the money I am ever going to get... so I understand that.. so use the same techniques you used before and don't let the internet worry warts discourage you..

look at it this way, your truck survived 16A in SD, and it survived Bozeman Pass, it will survive Eisenhower...if you have climbed some of those US Highways you have probably encountered worse driving conditions than the Eisenhower Pass.. that climb from Rapid to Mount Rushmore is fairly impressive...

 

[Jim W]

Why do you have to pull in 2nd gear with your truck?

I know my truck is different and the set-up is different but from my memory when I pulled on I70 these where my stats.

Smarty tuner set on level 3. Engine RPM in 5th gear was 2,100 RPM doing 55MPH. Boost pressure around 30PSI, EGT's 1,100F. Transmission sump temps 200F. See my signature for the complete set-up

My trailer is a 34RL Cedar Creek which I have weighed, the total combined weight of truck and trailer is 19,500LBS.

I was able to maintain the speed limit for most of the time without the exhaust braking from the VGT on the truck. But when I did lift my foot from the accelerator the VGT would engage. I did have to tap the brake pedal sometimes, but the truck and trailer were controllable in the downhill decent.

 

[GAmes]

I'm retired too... like you the money I have is all the money I am ever going to get... so I understand that.. so use the same techniques you used before and don't let the internet worry warts discourage you..

look at it this way, your truck survived 16A in SD, and it survived Bozeman Pass, it will survive Eisenhower...if you have climbed some of those US Highways you have probably encountered worse driving conditions than the Eisenhower Pass.. that climb from Rapid to Mount Rushmore is fairly impressive...

I'm retired too and know first hand the difference in cost in getting a transmission repaired at home, at my leisure, and breaking down far from home. My 1st gen that had an automatic had a transmission failure about 40 miles west of Rock Springs, WY while pulling an RV. No cell service so I had to ride a bicycle to Little America to call a tow truck that was capable of pulling both truck and trailer. Then, while the transmission was being repaired, I was stuck at the Rock Springs KOA for a week.

I had plenty of NV4500 failures while on the road as well, none of them were fun or cheap. Finally I found a way to get my speedometer to work with a six speed. After the upgrade, about 700,000 miles ago, I've never had another transmission failure. The OP's 48RE is the weak link. Maybe it will last, maybe it won't. If it isn't upgraded and fails I'll have a clear conscience. Will you?

 

[DaveHess]

Why do you have to pull in 2nd gear with your truck?

I know my truck is different and the set-up is different but from my memory when I pulled on I70 these where my stats.

Smarty tuner set on level 3. Engine RPM in 5th gear was 2,100 RPM doing 55MPH. Boost pressure around 30PSI, EGT's 1,100F. Transmission sump temps 200F. See my signature for the complete set-up

My trailer is a 34RL Cedar Creek which I have weighed, the total combined weight of truck and trailer is 19,500LBS.

I was able to maintain the speed limit for most of the time without the exhaust braking from the VGT on the truck. But when I did lift my foot from the accelerator the VGT would engage. I did have to tap the brake pedal sometimes, but the truck and trailer were controllable in the downhill decent.

Thanks Jim! So, I don't have to pull in 2nd gear. The 48RE for 2003.5 does not have a Tow/Haul function. Only a switch to turn off the OD. So that is what I do and then I let the 48RE do its job (leave it in "D"). That particular pull out of Rapid City, the truck did not shift above 2nd until the grade of the climb began to subside so to speak. At that time time she shifted to 3rd. I had mentioned in a previous post I have pulled the Bozeman Pass on I-90 in MT many years ago. If my memory serves me, she ran right up that grade without batting an eye at a GCW of 18,000. The pull out of Rapid City to Hill City was in traffic and red light to red light. This was a GCW of 20,800. I did not hammer on my truck nor do I at any time. A steady throttle and the truck "decided" to stay in 2nd until the highway began to flatten out. Then to 3rd we went. So, this is where my concern has come from as I have no frame of reference other than the climb out of Rapid City. IF my pickup slows down enough on the westward haul to the Eisenhower that recreates the down shift into 2nd to pull the camper up the grade, my knowledge base tells the Transmission temps are going to climb pretty quick as will the ECT. So as several responders to my original post have said, simply pull over and let it cool. to me that means, "wash, rinse, repeat". I think I have found there is no "fix" here in my current configuration. Its been 22 years of basically flawless operation. The 5.9L/48RE combination is what it is. I apologize as my initial intent and hope was for the owner of an early 3rd Gen who had pulled this section of I-70 with a load at their max GCWR to jump in and tell me what they did. Figured there had to be someone out there...

 

[Grumpy8811]

I'm retired too and know first hand the difference in cost in getting a transmission repaired at home, at my leisure, and breaking down far from home. My 1st gen that had an automatic had a transmission failure about 40 miles west of Rock Springs, WY while pulling an RV. No cell service so I had to ride a bicycle to Little America to call a tow truck that was capable of pulling both truck and trailer. Then, while the transmission was being repaired, I was stuck at the Rock Springs KOA for a week.

I had plenty of NV4500 failures while on the road as well, none of them were fun or cheap. Finally I found a way to get my speedometer to work with a six speed. After the upgrade, about 700,000 miles ago, I've never had another transmission failure. The OP's 48RE is the weak link. Maybe it will last, maybe it won't. If it isn't upgraded and fails I'll have a clear conscience. Will you?

sound alot like the worry wart's I was mentioned

 

[GAmes]

sound alot like the worry wart's I was mentioned

Actually it is a Boy Scout motto. Be prepared.