Performance at higher altitude

[OLEJOE]

I have a 2018 CTD that performs and runs great. But if I get above 5k ft ASL it acts crazy. Running with cruise on, it will start to pull (towing) and then kind of hang up until the speed drops then downshift and take off. The transmission and exhaust brake act screwy as well. My question is: has anyone else had or heard of this happening and what the cure might be? Just returned from a trip Albuquerque where it was 6-7k ASL and truck surges and acts so crazy then I got back to lower elevation and it runs perfect. ???

 

[mtnrider]

Lived in Colorado above 7000 ft for many years and never had an issue with any of my Cummins trucks. How much weight are you pulling and are you locking out 6th gear? I rarely run cruise control (especially when towing) unless it's completely flat stretch of road.

Is the truck still under warranty? If so take it in

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[OLEJOE]

Towing 7k TT and it will do the same on cruise in 5th plus the fuel pedal gets really touchy in 5th. It is still under warranty but they look at me like I’m crazy when I describe what it does. We’re at less than 200 ft ASL so it isn’t going to do all the crazy stuff. Just wondered if anyone else had the same problem. Get below 5k ft and it does awesomely.

 

[Bob Macknight]

check your tranny fluid level,and look to see if the tranny dumped any fluid out of the vent tube,had that happen years back traveling cross country tranyy acted up and let some fluid out the vet tube on top of tranny,i was told the change in altitude and the fluid heating up causes the fluid to expand thus the dump of fluid.

 

[sandawilliams]

Expect a 3% loss of power for every 1000' of elevation gain.

 

[mtnrider]

Expect a 3% loss of power for every 1000' of elevation gain.

Except the OP has a turbo diesel so that doesn't really apply..

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[sandawilliams]

Except the OP has a turbo diesel so that doesn't really apply..

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Didn't notice that but there will be some drop off. About 1.5% per 1000'.

Affects of Altitude on Diesel Engines (barringtondieselclub.co.za)

 

[jejb]

I've towed an 8k trailer over Monarch Pass (11k) and other passes in CO. No issues at all with my 18 CTD Ram, whether using CC or not. There must be some kind of altitude sensor in the system. I think I'd start looking there.

 

[mtnrider]

Didn't notice that but there will be some drop off. About 1.5% per 1000'.

Affects of Altitude on Diesel Engines (barringtondieselclub.co.za)

That is very true for some turbo applications but the variable vein turbo mitigates most of that. The loss of a modern Ram cummins at altitude is negligible. It should not be anything he can feel with his butt dyno.

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[Tumbleweed]

Perhaps take it in to a dealer at those elevations? They should know more & have the experience.

 

[OLEJOE]

I just wonder which sensor detects altitude ? I found a guy on another forum who has had the same problems with his DRW 3500 and hasn’t gotten it figured out. Maybe I can find a dealer service person who will listen to what I’m trying to tell him or her what it does when I get to higher elevations. It’s like you flip a switch. Was coming down a grade of approximately 10k feet and the exhaust brake wouldn’t work, the transmission would just shift to a lower gear when I let off on it. Got to the bottom at around 6,700 and exhaust brake started working again. I’ve been to the dealer and tried to explain what it was doing she evidently didn’t explain it to the technician and I got the all good answer. ???

 

[Dennis Shellito]

Perhaps take it in to a dealer at those elevations? They should know more & have the experience.

That sounds like the best advise, and they will be able to diagnose a problem that the lower elevation techs will blow you off as crazy and imagining things. My 2011 runs just as good up mountains as it does on flat ground at SL, which is fantastic.

 

[mtnrider]

I just wonder which sensor detects altitude ? I found a guy on another forum who has had the same problems with his DRW 3500 and hasn’t gotten it figured out. Maybe I can find a dealer service person who will listen to what I’m trying to tell him or her what it does when I get to higher elevations. It’s like you flip a switch. Was coming down a grade of approximately 10k feet and the exhaust brake wouldn’t work, the transmission would just shift to a lower gear when I let off on it. Got to the bottom at around 6,700 and exhaust brake started working again. I’ve been to the dealer and tried to explain what it was doing she evidently didn’t explain it to the technician and I got the all good answer. ???

MAP sensor reads the barometric pressure.

With that said it doesn't make what you are saying about the exhaust brake and it down shifting when you let off the accelerator? Is that under braking? What gear were you in? How fast? The torque converter has to be locked for the exhaust brake to work. Maybe your actuator is failing? Pretty common issue with these trucks.

I used to live at 7200ft and would drive to my place in summit county every other week which was ~11k ft and never had a performance issue due to/related to altitude.


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[OLEJOE]

That’s what’s weird about what it’s doing. Once I get back down below 5000 feet, it runs perfectly. Sorry for the late replying but my internet has been down at home and my cell won’t work without wi-fi. Thanks for all the advice. I’ll try to get it looked at next time I get high. Lol

 

[jdhreiss]

Just back from a week long trip through Sawtooth Mountains in Idaho - Towing and empty - I didn't see any issues up to 7,500 ft in my '13 with 87k miles. I think the O2 sensor(s) can tell the A/F ratio and adjust accordingly, but I'm just a shade tree wrench on a forum......

 

[daveinkailua]

What about gasoline, normally aspirated engines. I own a 2018 RAM 1500 with the 5.7 hemi and an eight speed transmission. I’ve towed my travel trailer with this truck from the day I bought it without any problems at all. I’m just getting back from a month long trip through out New Mexico and experienced a lot of transmission shifting problems at 7000 feet and above. I took it in to the RAM dealer in Durango CO where they pulled the codes from the OBD but there was no indication of a transmission issue.

 

[crash68]

What about gasoline, normally aspirated engines. I own a 2018 RAM 1500 with the 5.7 hemi and an eight speed transmission. I’ve towed my travel trailer with this truck from the day I bought it without any problems at all. I’m just getting back from a month long trip through out New Mexico and experienced a lot of transmission shifting problems at 7000 feet and above.

As mentioned above, naturally aspirated engines lose about 3% of power per 1000 foot of elevation. If you weren't using 89 octane fuel along with the higher elevations the engine was probably pulling all the timing it could to keep from knocking. The transmission was probably dropping gears due to the increased torque demand

 

[ppine]

Compared to the old days with carburetors that sputtered and vapor locked, modern fuel injection is like a dream.
I lived in Colorado for many years and did okay with carb engines, but really like the newer designs.
I had a logging site at over 11,000 feet. The old Jeep Wagoneer lost a little power but did fine.
People don't know what they missed.