Potential mechanical issue...

Are we talking about an automatic transmission perhaps being operated in manual mode?

 

If you are lugging below torque shes gonna shake and buck.

You are already downgrade and that jacobs braking is in your favor. Use the dam thing. It's nothing but a certain amount of gallons per hour. You already threw down 30 plus gallons hourly getting up and now you are stressing about fuel mileage getting down? It's a downgrade. Free foward motion. That jacobs is to keep everyone safe. Use it. Don't ride your brakes and cook them, if you really need them they might not be there at all.

I think someone has whipped you over the head too much on fuel mileage. Come off it. You are in mountains for crying out loud. This is not the place to get fuel mileage. Your jacobs brake is plenty good.

As far as transmission, you probably are in manual mode. trying to get the engine to turn over very slowly. That is not what engines are made to do. Get between torque and high horse on your RPM chart for that engine and keep it in the sweet spot. She will run much better and everything will be stable.

A bucking tractor is very angry with you. You are not doing something right. Let's see what we can do to smooth things over again shall we?

 

If you're climbing and stuttering you're lugging your rpm


Where is your rpm when this happens?

 

Probably 600

 

Don't do that with the accelerator, turn the engine brakes off or take yourself off of cruise.

The shudder is the engine brakes turning on and off, with the ecm trying to fuel the cylinders at the same time, in a matter of milliseconds. It isn't good on the engine nor the drive train.

Geeze learn how to drive the truck right.

 

You say you are looking for more like 75 or so?

You basically are saying you are being impatient with the speed and want gravity to take you up to 80 or whatever. if this is the state your rig is in, I am with Ridgeline on this, your engine is starved of everything. No fuel, no oil moving no nothing. And then you want more? No wonder your rig is fighting to do something.

You can do so much damage to a engine with no fuel pump output a jake that steals oil and trying to run outside of your company set limits of cruise and so on using gravity to force it.

My suggestion is simple. Set up your cruise for 65, accept that you wont do well at 68 or 72 or beyond. Back it down a little bit and allow that poor truck to at least run. You will know she is running well when there is no fighting back at you. Leave it that speed. You will get there eventually. You can only get there when you get there. It becomes more of a problem if you are being stressed and running late with dispatchers whipping you and filling your QC with call me messages... Make a new appt for delivery. Otherwise suffer a service failure or two until you are fired.

I hate to see a truck abused by gravity to run at 75 when there is nothing moving or flowing into the engine to do anything at that speed.

 

I'm usually doing 68. At what point is it detrimental to mpg regarding speed. Is it really that much of a diff between 65 and 68? I struggle on hills with this Columbia