2nd Gen Non-Engine/Transmission Poor Fuel Economy?

[ffken]

If i change gears from my 4. 10's to 3. 54's what kind of mileage and rpm change should i expect? Right now i run at 2700rpm going 75 and getting15 mpg city or highway doesn't matter. I was able to buy this truck because i told my wife to expect 20mpg per many tdr owners. I dont require the 23-27 i commenly hear about but could sure use some help! Thanks

 

[barbwire]

variables

KAldridge, According to what I read, there are so many variables to consider. Such as, tire size, dual wheels, single wheels, 4x4, height of vehicle,oils used,ratios,maintenance, performance enhancers, etc,etc. and the list goes on.

However, as per your question about changing gears, if you don't have a 4x4, and you can change them economically, I am sure you will see a benefit. One thing would be the amount of noise reduction with the lower RPM at the same speed ,that you now do. I would also think you would pick some mph gain also.

If you have a 4x4, then maybe you would want to consider a Gear vendor (not sure how it is spelled) auto overdrive unit that is in addition to your existing drive train. Then you would still have the 4:10 ratio when you needed it, and you would have the higher ratio when cruising. There are a lot more educated people on this subject than I, but I thought I would chime in and give my $. 02 anyway.

HAPPY THANKSGIVING

 

[Rebel_Horseman]

I have the 3. 54's in my truck and I turn a hair over 2000 rpm's at 70. At 75 I'm around 2350. My truck gets OK mileage... probably 16 or 17 with the winter fuel at 70. Before the winter blend and my Diablo, I was getting 18ish at 65-70. Bear in mind my rig is a 4x4. I'm hoping that once sping rolls around and the fuel is swapped back I'll be getting close to 20 or so, but all in all I'm satisfied with my truck's performance and mileage.



Brian [><]

 

[ProspectorTim]

Wow, two other replies in the time it took me to type this one up. As you can see, the answers are close to the same.....





I't would be hard to guess about your mileage without knowing more about the truck - 2wd/4wd, auto/5-speed/6-speed, year, mileage on it, tire size (stock?), etc.



Besides driving habits & conditions, a lot of other things can affect fuel economy too: bug deflectors, running boards, tow mirrors, ALL have an affect.





That said - My 99 4wd with running boards, bug deflector, automatic 3. 54 LSD - when driven conservatively is good for about 16. 5 around town and 18 - 20 on the highway. I HAVE got better (21 or 22 if I remember right) when I set the cruise control on 50 in Florida. But I live in Colorado, so that is not "normal" conditions for me.



75 MPH is just over 2000 RPM; less than 2200, I think. (automatic, in overdrive).





Don't overlook the obvious "mechanical" stuff that can affect the mileage, like the air filter, tire pressure, and IAT sensor; or some of the less obvious - what is the condition of the gear lube and transmission fluid? If automatic, when was the last time the bands were adjusted? How good/bad is the steering?

Are all the intercooler clamps tight?

 

[ffken]

SORRY, just figuring out how my user info works. man you guys reply fast. Maybe my truck info below will help anyone else making a prediction. by the way Prospector, how hard is it to change my iat? how do i know if it is working correctly and what is the cost. ??? Sorry, i'm no mechanic.

 

[Joe G.]

The only combination for fuel milage worse than yours would be the same truck with an auto trans. 3. 54 gears would help, but not much. I don't think you could tow it and get 20 MPG.

 

[dvaughan]

Poor Fuel Economy

KAldridge, Try this site. http://www.smokindiesel.com/Technical.htm

http://www.dodgeram.org/tech/dsl/sensors/IAT/clean.htm



I have cleaned mine with brake cleaner and it did inprove my mileage. I don't think they are that much if you want to buy a new one. Go to Cummins to buy one, it is cheaper then the Dealer.

 

[DwayneKelch]

Yes, what everyone else has said. There are so many variables, in addition to gear ratio, that all have to be considered. Each will add just a little more to increased fuel mileage.



The biggest increase I noticed was switching from dino to synthetic lubes (Amsoil). I average just over 20 mpg, even on winter fuel...combination city/highway. I took a trip to Alaska this year and averaged 20. 8 mpg, averaging 65 mph.



Good luck... it's there, you just have to find it.

 

[JoshPeters]

I have found that your speed/engine speed has alot to do with your milage. I normally average 17ish for milage, no matter city or hwy. I have gotten as good as 22, but I was running 60 cross Wisconson, in no hurry to get where I was going. On the way back I got 16, I was running 80mph, in a hurry.





Josh

 

[WadePatton]

The more I BOMB mine the better the MPG's get. Started in the 17's, now it's always high 19's and low 20's.



Gauges, DD injectors-size of your choice, timing/fueling box-of your choice. EAR TO EAR grin--no choice!



IAT is easy once you find it. Top of the engine, driver's side, close to MAP, but further toward fire wall and in intake.



http://www.dodgeram.org/tech/dsl/sensors/IAT/clean.htm

 

[bmoeller]

Originally posted by ProspectorTim

Besides driving habits & conditions, a lot of other things can affect fuel economy too: bug deflectors, running boards, tow mirrors, ALL have an affect. [/B]

Have following, as stated above. Plus 4. 10's and what is in my sig, and can get 16. 5 running 75 in the summer. High 15-16 in town during the summer.

 

[RKohn]

18 avg forever. mostly hwy @ 75-80. best of 20 worst of 15.





any increase due to mods is usually offset by accompanying heavier right foot.

 

[Jeff H]

Well the last time I figured my mileage I got 21. 03 miles to a gallon. Thats also with 285/75 tires. City and HWY driving

What helps.

-Fresh fuel. Meaning a busy fuel station. Gets at least a load of fuel once a week from the refinery.

-Timing is where I would start. Set it up between 15 to 19. Fifteen is most common.

Then in either order.

-A better air filter.

-Strait through exhaust. If its to loud then try a Walker muffler.

If you do over 70 you will not see 20 mpg.

If yer hauling the world behind you. I doubt you will get 20 mpg.

If yer drag racing brand X trucks you may not hit 20 mpg.

I would rather spend the money on a good mechanic to get my mileage improved. Other wise OPEC will appreciate your business.

 

[Joe G.]

He has a 3500 4X4 with 4:10 gears. Is anyone getting 20 MPG with this kind of truck?

 

[DDT]

I have a 2000 3500 4x4, 5 speed, 410 LSR, 114K The best I have got was 17. 2 BUT I have to drive like gramps and a top speed of 65. My normal is 15. 5 I like driving 70 mph. The EZ box did not help in empty fuel mileage but it helped alot when pulling trailers. My box went bad & I sent it back, I had to haul my tractor & hoe to the farm with a head wind. I got the cab on for winter use, I had it to the floor most of the time. I need my box back.