MPG vs HP Compromise

[Ronmar]

Yeah, I've recalibrated it. Even got a new Throttle Position Sensor. Mine is one of the harder-shifting trucks, which only makes the shifting more annoying.

Hey when you ran the TCM thru the routine to relearn 0-100% TPS and relearn the shift points, did you first confirm the pedal rotates the governor linkage between the idle and full RPM stops? AND fully warm up the engine and trans before you began?

 

[Awesomeness]

Yours is a WTEC2, i have seen some screenshots of the trans controller programming, and it appears that auxiliary hold was possibly enabled on non winch trucks as a default auxiliary input function(Wire 153 to signal ground 161B). When enabled this overrides the normal shift parameters and holds the trans in its current gear. you would still need to get it into 7th gear, but once there it would hold it there as you backed off to the lower cruise speed…

I'm not sure I followed that. Yes, mine is a WTEC2. It shifts up into 7th very reliably at 60-62MPH (with 3.07:1 gears), and back down into 6th at that same speed range.

 

[Ronmar]

I would be curious what RPM it kicks down from 7-6. unless the TPS indicates to the transmission that you are maintaining speed it would likley downshift somewhere around the peak torque point 1500-1600RPM? The procedure is a little buried, but you do 5 power on-power off cycles in succession. On the 6th power on it clears the shift memory. You then fully depress and release the accelerator pedal to teach it the minimum and maximum TPS positions. Then you push start and go for drive up and down thru all the gears to let it relearn shift points. You would want to make sure the pedal works the governor linkage between the hi and low stop screws, and already warmed up would also be good.

If the trans controller was programmed for the hold feature, you could add a switch to hold it in 7th when you back down below 60. If you don’t have a winch, you could probably get this feature programmed if yours isn’t already there.

 

[coachgeo]

If the trans controller was programmed for the hold feature, you could add a switch to hold it in 7th when you back down below 60. If you don’t have a winch, you could probably get this feature programmed if yours isn’t already there.

it drops out of 7th where if you have this "hold" feature activated?

 

[Awesomeness]

I would be curious what RPM it kicks down from 7-6. unless the TPS indicates to the transmission that you are maintaining speed it would likley downshift somewhere around the peak torque point 1500-1600RPM? The procedure is a little buried, but you do 5 power on-power off cycles in succession. On the 6th power on it clears the shift memory. You then fully depress and release the accelerator pedal to teach it the minimum and maximum TPS positions. Then you push start and go for drive up and down thru all the gears to let it relearn shift points. You would want to make sure the pedal works the governor linkage between the hi and low stop screws, and already warmed up would also be good.

If the trans controller was programmed for the hold feature, you could add a switch to hold it in 7th when you back down below 60. If you don’t have a winch, you could probably get this feature programmed if yours isn’t already there.

Yes, I've done that several times, for several reasons, including the replacing of the TPS. The procedure, for both WTEC2 and WTEC3, are here in my "Common Fix" document in my signature.

 

[Ronmar]

it drops out of 7th where if you have this "hold" feature activated?

Don’t know. Maybe never, Not a lot of info available on it. But more likely it would override the hold as it approaches idle or some other preset low or high RPM. Like when you select a lower gear with the arrow, if the engine reaches peak RPM, it overrides your selection and upshifts to protect the engine. That info is probably in the brogramming somewhere…

 

[coachgeo]

Don’t know. Maybe never, Not a lot of info available on it. But more likely it would override the hold as it approaches idle or some other preset low or high RPM. Like when you select a lower gear with the arrow, if the engine reaches peak RPM, it overrides your selection and upshifts to protect the engine. That info is probably in the brogramming somewhere…

would this hold any gear from shifting up too? aka...... usable as manual button to access lock up like a Pacbrake programing would do automatically if TCU was programed for such?

 

[Ronmar]

I suspect it would, but you would have to get the truck to shift down to that gear first, same as using the down arrow. And like the down arrow, I suspect it would be overridden by high RPM for safety… you can read about it in the appendices of the MD3060 troubleshooting manual… and of course wether the system is even programmed for it is yet another question… if you can get in to check that programming, you could just as easily enable the ex brake automatic 4th gear kick-down…

 

[coachgeo]

I suspect it would, but you would have to get the truck to shift down to that gear first, same as using the down arrow. And like the down arrow, I suspect it would be overridden by high RPM for safety… you can read about it in the appendices of the MD3060 troubleshooting manual… and of course wether the system is even programmed for it is yet another question… if you can get in to check that programming, you could just as easily enable the ex brake automatic 4th gear kick-down…

since thought over time of folk fiddling with this we'd pretty much decided there is no pacbrake programing in the 3116 FMTV's (that spot in TCU was used for PTO programing or something to that effect? ) ...... thus was going forward with there is no such luck in that area and it will all have to be manual activated situation . Hence one reason why considering turning driver seat right arm rest area on the dog box into a USS Enterprise Captians chair arm rest.. with nestled into it the Trans shifter etc.

but this is different topic and will stop this here so not to hijack this thread on HP/MPG compromises

 

[Ronmar]

Its only an issue if you have a winch truck, the aux input can be reprogrammed on any other truck for exbrake kickdown/pre-select.

 

[Keith Knight]

I finally hit the road and figured I would give this post an update. With all the tanks full and all of our gear in it I took it to the scale and it weighed in at 26,800lbs!
I’m happy to report I’m getting 6.5mpg! I was expecting it to go down but nope. Oh and I’ve decided not to drive it any faster than 55mph and being gentle on the acceleration.