2nd Gen Non-Engine/Transmission Mileage.... 11-14? what is wrong?

[cuevas623]

alright so I just got a my truck(99' 2500 3. 55 gears auto) I am only getting around 11-14 mpg and I know that that is not right most of the time I amnot going over 45 cause our speed limits suck but even on long hauls done the highway I am only gettingabout 14. I need som eserious help with this. The military does not pay that well!!! oh and I got this truck for 5,000!!!

 

[JLandry]

Your question was already answered in post number 2 here:



https://www.turbodieselregister.com...nsmission-1998-5-2002/200838-gas-mileage.html



Start by changing your IAT (Intake Air Temp) sensor, your coolant sensor, your fuel filter, your air filter, and if all that doesn't help, also change your MAP (Manifold Atmospheric Pressure) sensor.



Regards,



John L.

 

[DCreed]

also lock converter as often as possible.

 

[cuevas623]

Alright kind of new to all this what exactly do you mean by lock the converter. do you mean like try to hit a speed where it locks up or what?

 

[EKlem]

There are many factors that affect mileage include wind resistance, rolling resistance, drivetrain efficiency, weight, and the driving style.

If your problem is in the drivetrain, changing your filters and checking the sensors is a good place to start. Your automatic transmission could also be hurting you. The torque converter is like a clutch at the front of an automatic transmission and it is designed to slip a lot of the time essentially creating extra gearing. You can install a switch that will cause it to lock up and not slip like a clutch when it is fully engaged. The problem with a slipping converter is that it is turning rotational energy into heat.

Wind resistance is really important at higher speeds. Are you running larger tires? If so, this is killing your mileage because of the extra wind and the extra rolling resistance and rotational inertia.

Rolling resistance can have a very large effect on mileage if something isn't right. Make sure that your tires are aired up and that your brakes aren't dragging and all of your bearings are good(feel for heat after driving).

Another big factor is your driving. I have no idea how you drive but most people can get a few mpg better if they just think about it. Speed and acceleration are killers. Using the brakes also hurts you so try to plan ahead enough so that you can coast rather than braking.

Good luck getting your mileage up.

 

[Davcruz]

I would like to know the answer to that also. Is there a way to lock the converter manually or do you mean install a switch?

 

[cuevas623]

yeah that is a good question? I thought it jsut did it on its own.

 

[FLynes]

The converter will lock up on its own, but only when it reaches a certain speed. There are companies out there that sell boxes to manually lock your converter; this is especially convenient, if you want to put on an exhaust brake.



I started losing MPG's with my '01... went from a steady 19/20MPG down to 14MPG, but I have 4. 10's. There are a bunch of variables which play into why, but I think that with my situation, the VP44 was starting to die its slow death, which is why I just traded it; I'd rather have a kick-butt interior with tons of space, if I'm going to get crappy MPGs.



I would follow JLandry's suggestion and start with the IAT; it's a cheap part to replace... buy it from Mopar Parts for Dodge, Chrysler and Jeep: MoparPartsAmerica They are infinitely cheaper than the dealer. Air filter, fuel filter, fluids, etc.



With 3. 54's you should be getting better than what you are.



Good luck.

 

[DCreed]

TC lock up can be found by searching here under "mystery switch"

 

[WFyfe]

ultra low sulfur diesel( ultra lame shaatty diesel)winter grade fuel with lots of idle time could be the problem with a heavy foot, thats about what i get, it started to get above 50 degrees so i dont need the high idle any more, maybe my mpgs will improve

 

[Houser]

Yep sounds like the first reply had it right. Your truck is a little old and needs a tune up. A good running CTD with 3. 54 gears should get over 20 MPG at normal HWY speeds.

Houser

 

[RJMurphy]

Yep sounds like the first reply had it right. Your truck is a little old and needs a tune up. A good running CTD with 3. 54 gears should get over 20 MPG at normal HWY speeds.



Houser

I wish, my 99 3500 with a nice aerodynamic cab high bed cover would never get over 17-18 on the highway @65MPH, and that was before the ULSD. With the new fuel its down to 15-17@65. This is with 3. 55 gears, and a DTT converter and trans. 2 WD truck with stock tires @ 65PSI

 

[InfernoB]

Out of curiosity. Are the tires the correct size, and the speedo correct?



That's the first place to look when you get a new to you truck.

 

[cuevas623]

Well the tires are 265 rather then 245 which I am sure throws it everhead console says. I know those are off by a little. so basically I need a tune up.

 

[Hammer]

24v trucks with 3. 55's traditionally have worse fuel milage numbers than the 24v's with 4. 10's. Those motors are not low rpm units like the older 12v's and do like to be spun harder to be more efficent... ..... Andy

 

[Forrest Nearing]

if you're only doing 45, keep it in drive, not OD

 

[cuevas623]

So it IS alright to keep it out of OD this is not hard on the transmission? What is a good website to find the"mystery switch". Is this mod also hard on the transmission?

 

[cArNiVaLwOrKeR]

24v trucks with 3. 55's traditionally have worse fuel milage numbers than the 24v's with 4. 10's. Those motors are not low rpm units like the older 12v's and do like to be spun harder to be more efficent... ..... Andy

Andy,



What RPM's are you suggesting is to be the Sweet Spot?



JoeLee

 

[CFAR]

If you are running winter fuel, that is the problem, don't throw a lot of money at it until you get summer fuel and test, mine got (01', 3. 54, 6sp, HO, 100hp inj, etc. . ) got 21mpg's normal, 14 winter fuel.

 

[Joe Mc]

Sweet spot is 1900 - 2100, she really sings her appreciation working in this range.