Correct RPM Change

[WStrmiska]

Hi guys, wondering if some of you could help me out. What rpm range do you shift not carring a load and carrying a load. This is my first diesel truck that I have owned and want to treat it right.

The owners manual dosen't say any thing about this, at least I didn't see it. I'm going to be towing a 3 horse, LQ Bison horse trailer. I think the total gross weight is 12,000 #. I will be towing in the mountains alot this summer and fall. Any answers greatly appreciated.

Wild Bill

 

[Vaughn MacKenzie]

WStrimska, here's what I usually do:



Unloaded

Light acceleration, level: Approx 1900

Gradual acceleration: approx 2200

Moderate-hard acceleration: Upshift approx 2700





Loaded

Light acceleration, level: 2300

Gradual acceleration: 2600

Moderate acceleration: 3000



Main thing is to not lug it. If you are using more than 1/2 throttle you should be over 2000 RPM or so. When I tooling around town easy on level ground I run between 1300-1700 rpm.



Hope this helps.

 

[klenger]

Vaughn's numbers seem reasonable

 

[Vaughn MacKenzie]

klenger to be honest I have't really watched my RPM that close, I just took a good guess at it. I'll pay closer attention tomorrow and see where I shift :-laf

 

[WStrmiska]

Thanks for the information guys. I'll feel better knowing I will be shifting in the right rpm ban. Thanks again.

 

[DPKetchum]

I jusft drive and shift were the need calls for! I've NEVER looked at tachs to much even in BUILT hot rods. I do on my TRACTOR when running PTO speed thats about it. Just drive and shift.

 

[cbunt1]

I guess the big-rig driver in me comes out here. I shift progressively.



I take off in the highest gear that I can "0-fuel' in--i. e. ease out of the clutch, and no fuel until I'm completely engaged. Usually this is second.

I then shift 2-3 at around 2100 RPM

then 3-4 at around 2200 RPM

then 4-5 at around 2300 RPM

then 5-6 at around 2300 RPM (or when I reach crusiing speed--whichever comes first).

If I do make a granny-gear take off--that shift is usually at around 2000



I pull to the next gear at a point that I'll slide in right around 1600.



I never full-pedal it when I'm working it, thus I don't truly lug it.



The type of driving/shifting is not what most of us do with these pickups--it's more a throwback to my 18-wheller days--and given that I'm hot-shotting now, it seems appropriate.



I shouldn't admit it--but I will--I'm also a float-shifter. If it won't float right into gear, the engine/transmission's saying not now fella--so that's how I've developed the progressive pattern--it just works so well with the truck.



Bottom line--ease on it, and let the engine tell you. You'll find a spot (especially when pulling) where there's a gap between torque and horsepower at around 2400--then it'll come alive again until around 2600--a useful spot for a long grade.



BTW--for those of you who wonder--I average around 14 MPG with that setup--the trailer is a 40' flat, and weighs 9100#, and my average payload is 5-10,000# -- so gentle and steady seems to pay off with these trucks.



On the other hand--just drive it. It'll tell you when you ain't in the right ranges, and I doubt that you will hurt it unless you take it to the realm of truly abusing it (and if you can't tell you're abusing it at that point, well..... )



JMHO. YMMV.

--Chris

 

[DannyW]

Talking about shifting under heavy acceleration... ... .



One thing I've seen, as a graduate from the old 12-valve engine, is that the throttle response has a time lag I'm not used to. My old engine would immediately unload as I backed off the throttle getting ready to hit the clutch. This new HPCR engine will not, and I've seen 3500 on the tach a couple times in mid-shift (especially going 5th to 6th on the on-ramp). Just like it won't "grunt" like the 12-valve when you tap the throttle idling at a redlight, it takes the fuel delivery a fraction of a second to back off under load. So be careful about hitting the clutch too soon on upshift under load. I imagine the "brain" probably recorded those RPM spikes for later use against me, eh?

 

[cbunt1]

Danny: Agreed. I did notice that the "Grunt" comes back after removing the factory muffler--with the glasspack, I get the grunt like the larger (L-10, N-14, ISX) Cummins engines.



I think the throttle lag you mentioned is a big driver in my shifting style--I was losing too many RPMS in my foot-timing, or revving the engine through neutral--made me feel like I didn't know how to drive a manual.