Hey everybody,

With rising fuel costs I want to kinda squeeze as many miles as I can out of a tank of gas. I have an O/D off switch on the dash but never used it untill resently. I noticed that it gives me better response in the city and i do alot of city driving, harldy ever go above 50mph. So i was wondering while driving in the city should i have the od off and will it get better mileage because before i noticed sometimes it had a hard time downshifting from o/d in the city. And when i go above 50mph just switch it on? Thanks again,

 

You really don't need OD unless you're on the highway. The bad part is that when the truck is turned off, the switch resets itself back to 'On'.

 

I leave od off while:
- I am driving around town or other stop and go type situations,
- when towing (unless I am on a nice flat stretch of road that I can maintain od with no problems)
- When driving on the highway and I get into areas that cause my trans to keep shifting in and out of OD (like in the mountains).

 

I recall a post once were someone explained how they set it up so off was the default instead. Not sure if it was on this forum or not, but I'll do some looking.

 

gotta use a relay on the wiring for the button... not hard...

http://www.dodgeram.org/tech/mods/tr..._inverter.html




tells ya how and what to do

 

Thanks for the link. I've been needing to do this since the 35's went on......

 

your welcome!!!!! i did this a while ago... its one of them things that makes it anoying when you gotta do it all the time

 

here's an old post from another Dodge forum in 2003:
--
I have read a few places where Ram owners have said that they get better MPG
in city driving with the OD button pushed to Off. I was curious about this
and have been doing a small mpg experiment to see if this would be true for my
Ram.

For the last six tankfuls I have been recording the MPG and then switching OD
off or on during the next tankful. I fill each tank until it is full, then
rock the truck and fill again until I can see gas level with the spring loaded
plate. Mileage was about 330 miles for a tank, so the 3 tankfuls below
represent about 1,000 miles of driving. The odometer readings were corrected
by a factor I got previously by checking against mileposts and GPS readings.
{my odo is off 12.8%)

OD turned off runs:

7-19-00 14.32 mpg Amoco87
7-29-00 15.17 mpg Amoco87
8-8-00 14.23 mpg Amoco87
---------------------------------
average 14.57 mpg

OD turned on runs:

7-12-00 14.16 mpg Exxon87
8-17-00 14.25 mpg Amoco87
8-24-00 15.49 mpg Amoco87
-------------------------------
average 14.63 mpg

Both times when the MPG broke 15 mpg I had made a 80 mile round trip to
Raleigh NC on I40 during that tank. I believe these 'highway' trips account
for the slightly better mpg on that tank. The rest of the driving was mostly
stop and go suburban driving.

I don't believe the difference between 14.57 and 14.63 is what engineers would
call 'statistically significant' and it is best to say that the MPG was the same on
my Ram, whether the OD was off or on.

The variation in the six MPG tests above also indicate that I would need to do
about 6 more such tests to have reliable data to really conclude as to whether
OD off/on either helps, hurts, or does not matter to MPG.

This city driving test also points out the penalty in MPG that the Ram pays
for accelerating and stopping its heavy weight. {my 1500 2wd CC Ram weighs
5400 lbs versus 4950 when totally empty}

For comparison to these 14 MPG city numbers, on 6-25-00 I made a 310 mile
round trip from Durham to Wilmington with the same Ram at a cruise controlled
steady 60 mph. The 'highway only' MPG on that trip was 22.7.

update

I have since made 3 more 300 mile long mpg tests in city driving since i
posted the original 6 tests. My test results now look like this:
-----------
OD turned off runs:

7-19-00 14.32 mpg Amoco87
7-29-00 15.17 mpg Amoco87
8-08-00 14.23 mpg Amoco87
9-08-00 13.53 mpg Amoco87
---------------------------------
average 14.31 mpg

OD turned on runs:

7-12-00 14.16 mpg Exxon87
8-17-00 14.25 mpg Amoco87
8-24-00 15.49 mpg Amoco87
9-01-00 15.03 mpg Amoco87
9-12-00 14.35 mpg Amoco87
-------------------------------
average 14.66 mpg

As you can see, so far the OD on/off difference seems to be small with a
slight 0.3 MPG edge to leaving OD on while in city driving. That is about a 2%
difference.

Note also how much the MPG jumps around. All realworld tests have 'random
variation.'

The overall average of nine tankfulls is 14.5 mpg
but varies from 15.49 to 13.53,
even though the driving was over pretty much the same streets with the same
gasoline.

If I had done just two tests, and had by chance gotten the low 14.16 for the
OD on, and the high 15.17 for OD off, I would have falsely concluded that OD
on really hurts in city driving.

To really find reliable MPG numbers for Rams in city driving you need to do
multiple tests. I intend to do at least 3 more 300 mile city tests to see if
the present trend continues.

This is on a 5300 lb Ram ClubCab 2wd with the 46RH auto, the 5.9V8 and a 3.21
diff ratio.

If you have the 3.55, 3.92 or 4.10 diff ratio, I would guess that the OD
on/off test would show the OD on helps a little more than with a 3.21 - but
that is just a 'guess.'

 

After pulling a 10k lb 5th Wheel Camper for several years, the OD switch was exclusively used to prevent premature transmission failure due to "auto down-shifting" pulling the heavy loads. I ruined both chevy and ford tranny's while pulling with OD on.
MPG wasn't the issue when pulling, although with the F350 4x4 Powerstroke it was only 9 mpg when pulling that trailer, I would get 16 normally.
Seems to me that higher RPM translates to higher consumption, at least it's that way for all other engines I'v ever dealt with. That would tell me that any driving that can be done at the lowest practical RPMs for the speed is the best way to better your mpg.

IMO

[IMG]local://upfiles/33151/967176AE4209408790BF52415FA752D3.jpg[/IMG]

 

Ya, I don't use overdrive for gas mileage, I use it to help prevent my trans from shifting excessively when not needed.