David,

Sounds like you've got the answer here. Attached photo from earlier today is pulling about 6K Lbs up a pretty good (3-4%, I don't think the gauge was correct, on the down hill side of this same grade it warns of 7%) hill. Somewhere about 6000 ft in altitude. This was about half way up 10 miles or so of hill, going 75 and then going to WOT. Speed didn't really change, crept up very slowly after down shifting to 5th. Temps are up there but didn't get any higher and boost was no where near max. Have to believe it was intentionally protecting itself.

 

Just to clarify, the pitch angle of the truck gauge and the grade markings on the road are not the same thing. It's not a direct relationship.

I forgot why or I would explain it, but the grade sign on the highway is usually about double the figure in the truck display.

Is it truck=degrees
Road sign =rise/run percentage like the right triangle. Length of distance forward, distance to top from base. Take that right angle and come up with the percent of difference between the two?

 

Ruschejj,

Makes sense now! Thanks, I'll have to do some research and determine what the real relationship is.

Edit: And the Wiki answer is:

 

Truck is degrees and roads are percent.

1*=1.7%
2*=3.5%
3*=5.2%
4*=6.98%
5*= 8.7%
6*=10.5%

 

Dang it! I hate when I derail things. But I wanna know, you're supposed to be able to use math to get 5.71 from 10 degrees or vice versa.

So,what of 10 degrees is 5.71%?

How can a percentage of 11.31 degrees = 20?

 

11.31 degrees is 19.74% isn't it?

 

Think of it this way:

The grade percentage is the percentage of rise over run. So if you move 100 feet forward and rise five feet, you would have a 5% grade because your rise is only 5% of your run. So you can use trigonometry to calculate the grade. So on a scientific calculator, Tan-1 (Opposite/Adjacent) equals the degrees of the angle. So Tan-1(5/100) = 2.86 degrees.

See:



So in summary, a 2.86 degree angle will make you rise 5 feet for every 100 feet horizontally travelled.

 

I come up with 11.17 degrees.

 

You are only pulling 6k and can't accelerate. This seems more and more to be an intentional programing issue. My question is why? A 6-8k trailer load should not pose any overheating or EGT isue for this motor, yet this motor is reducing power. This must be to protect something on the motor but what is it? Isn't this truck rated at pulling another 14,000lbs. Tack another 14,000 on these going up these hills then worrie about the engine heat and EGT's. I am really confused as to this condition. Our trailers at 6-8K can't be pushing the limits of these motors. Again if so what would 20-24K do to them? It seems to be a blanket programing issue.

One more example. I had a 40' diesel pusher motor home and towed a 26' care hauler. This coach had a 300hp cat diesel with 880lbs tq. Now I understand these are different motors but torque is torque. This motor had 80 more lbs of torque and was pulling almost 3 times the weight my 250 is. This set up would accelerate on these same hills. I also understand there was different gearing. But I could go 80 or more on these hills.

On a side note I have slowed down as I have aged.

I just like extra power to get around slower moving units on these hills!

Who is going to find a solution to this delema? Lets Help this thoroughbred run!

 

Just had another thought. Maybe the trucks programing is changed when a trailer is attached. When I tow my 8,000 lb trailer going down hill even on a 6% grade I do not have to use my brakes much at all. Lower gears on the truck actually handle that weight. Instead of hooking up with the trailer brakes, maybe I could have an adaptor for lights only put on the trailer. Maybe the truck would not change the power curve that way?

Has any one tried this?

 

Stop at the bottom ofte hill and unplug the trailer

Sam

 

I am impressed....... You remembered your Math Class stuff

 

Ok, thanks for the grade info.

I just don't get the problem. I towed my fifth wheel camper 400 miles yesterday but it was all flat ground. Still, thinking about this forum, I pushed it hard at times to see if I could detect anything going on.

My camper is about 11k pounds, M6 will cause me to lose speed on a decent hill, it takes a moment to gain speed 65-75 on flat ground. But this is normal and I had 12-17mph winds around me. I go into M5 and it just flat goes, takes a real mountain grade to slow this gear down with my camper. Accelerating on an uphill on-ramp is no issue, I just shift 2-3-4-5 at about 2200 rpms and I'm going 70 rather easily by the time I need to merge.

I tried, could not detect any sort of defuel at any time. I don't have a grade and altitude to play with though. I'm in Daytona, FL. Camping here for the next 10 days.

 

Try borrowing another truck if possible, and try the same grade. That would give you an idea how it is suppose to be.

I've got alot of hills, but nothing that is long. I notice nothing like your situation.

--
Gordon

 

Gaining speed on a hill is the issue. Getting up to 60-65 from a ramp will happen no problem even up hill. Try holding 60-65 on a 6% hill then floor it as if trying to get around some one and see how it works.

Thanks