Over drive question

AfricaJeep · **Posted:** Mon Apr 02, 2007 9:24 am

After having my Liberty for nearly 4 years, I still do not understand how the over drive works and when is the best time to use it :cry:

. I have searched this and other forums and I am still non the wiser.

So here goes:
1. When do I disable the overdrive?
2. Is it better to use overdrive in city driving or to disable it? My daily commute consists of 15km of traffic jams with 80% spent at 25 - 30 mph and max speed of about 45 mph.
3. When climbing up a mountain pass where the road is approx 2 mile long and climbing at a 45 degree angle, do I switch off the O/D?
4. On a road that has lots of hills - similar to a rollercoaster

- O/D on or off.

Thanks

hyedipin · **Joined:** Thu May 11, 2006 10:20 am **Posts:** 1667

Towing only, possibly. I have never found overdrive useful, I am doing mixed city and highway driving. Someone else can give you a technical explanation, but think of overdrive as locking your auto tranny to 3rd gear. Maybe 3,5 gear?
Also you can use overdrive when you need extra force like getting out of a ramp into highway, or climbing and it hesitates to downshift, (*I just floor at that point*) just hit O/D off and it will get going.

Dje Ryu · **Posted:** Mon Apr 02, 2007 9:37 am

The only time you need to keep it off is when towing or if you happen to have a LOT of weight in your kj.

AfricaJeep · **Posted:** Mon Apr 02, 2007 9:42 am

Dje Ryu wrote:

The only time you need to keep it off is when towing or if you happen to have a LOT of weight in your kj.

Like when I am driving, instead of my wife

I weigh 250 pounds and she weighs 105 pounds :oops:

hyedipin · **Joined:** Thu May 11, 2006 10:20 am **Posts:** 1667

AfricaJeep wrote:

Dje Ryu wrote:

The only time you need to keep it off is when towing or if you happen to have a LOT of weight in your kj.

Like when I am driving, instead of my wife

I weigh 250 pounds and she weighs 105 pounds :oops:

Well, that doesn't qualify..

If you got three of your friends in your jeep, heading over to weekend barbecue, or worse yet, returning from it.. now that qualifies for an O/D Off moment..

just kiddin ya. To be honest, I have never felt the weight of my passangers on my jeep, and let me tell you some of my relatives can compete with you.

Joe Jeep Owner · **Posted:** Mon Apr 02, 2007 10:11 am

My OD is on all the time, the Jeep seems to run better with it on. I guess I shouldnt be doing that? I'm on almost two years of it being on all the time. LOL

hyedipin · **Joined:** Thu May 11, 2006 10:20 am **Posts:** 1667

Joe Jeep Owner wrote:

My OD is on all the time, the Jeep seems to run better with it on. I guess I shouldnt be doing that? I'm on almost two years of it being on all the time. LOL

you mean off?, If it is ON and no towing, there should be no problem...
if Off, what's your mpg like!?! O/D Off keeps on high rpms unnecessarily..

Joe Jeep Owner · **Posted:** Mon Apr 02, 2007 1:48 pm

It's ON all the time, no towing. Is that bad?
Mileage isnt that great but no worse than it should be compaired to others, although I have never gotten the 21+ mpg that others have stated here.

Highway miles on long trips is a lot better than my daily mixed commute, but should I not be using OD?

gopherbeats · **Posted:** Mon Apr 02, 2007 1:50 pm

Mine is usually on. Except when I am about to get on the highway.. or about to go up a long hill.

hyedipin · **Joined:** Thu May 11, 2006 10:20 am **Posts:** 1667

Joe Jeep Owner wrote:

It's ON all the time, no towing. Is that bad?
Mileage isnt that great but no worse than it should be compaired to others, although I have never gotten the 21+ mpg that others have stated here.

Highway miles on long trips is a lot better than my daily mixed commute, but should I not be using OD?

ON is normal position, if you turn OFF then the mileage will decrease.

jerbacher · **Posted:** Mon Apr 02, 2007 2:10 pm

I sometimes turn it off when going down a long hill and trying to maintain a low speed, such as a long hill in a 35mph zone. Works well as hill descent control.

Maximum Carnage · **Posted:** Mon Apr 02, 2007 2:10 pm

Mine is always on, except for when towing. Or when torque is needed.

sleeve84028 · **Posted:** Mon Apr 02, 2007 2:32 pm

Mine is also "always ON" [meaning there is no O/D off light displayed on the insturment cluster]

I turn the O/D off for:
1) TOWING
2) (Ocassionally) if I need to slow down on the expressway to get behind a car that is going just a tad bit slower than me

Cdsbow1 · **Posted:** Mon Apr 02, 2007 5:10 pm

Overdrive can refer to two different things. An overdrive is a device which was uscommonly ed on rear-wheel drive automobiles to allow the choice of an extra-high overall gear ratio for high speed cruising, thus saving fuel, at the cost of less torque. It also refers to a combination of gearing inside a transmission or transaxle which results in the output speed being greater than the input speed. In the latter case, "overdrive" does not refer to a physically separate identifiable part/assembly. Generally speaking, overdrive (OD) is the highest gear in the transmission. Most automatic transmissions have 3 speeds and overdrive (fourth speed). Overdrive allows the engine to operate at a lower rpm for a given road speed. The overdrive consists of an electrically or hydraulically operated epicyclic gear train bolted behind the transmission unit. It can either couple the input driveshaft directly to the output shaft (or propeller shaft) (1:1), or increase the output speed so that it turns faster than the input shaft (1:1 + n). Thus the output shaft may be "overdriven" relative to the input shaft. In newer transmissions, the overdrive speed(s) are typically as a result of combinations of planetary/epicyclic gearsets which are integrated in the transmission.

Using overdrive gearing, the car's engine RPM goes down. This reduces engine wear and normally saves fuel.

LiLredLibby · **Posted:** Mon Apr 02, 2007 10:12 pm

In todays vehicles it's actually considered "AUTOMATIC OVERDRIVE".It should only come on at about 45mph.There's really no need to turn it off unless your hauling heavy loads only on hilly areas,to keep the tranny from up and down shifting so much.

Jeep4me99 · **Posted:** Mon Apr 02, 2007 11:44 pm

the only time I turn mine off is off-road in the sand so the transmission doesn't keep shifting. Other than that i don't really use it. not many hills in Florida.

AfricaJeep · **Posted:** Tue Apr 03, 2007 4:05 am

Thanks for all the replies.

The reason I was querying this is that for Easter we are driving down the east coast of South Africa (called the Garden Route). This route consists of 340 miles of lots of hills and three mountain passes. The first one, climbs to an elevation of 1400 feet above sea level. If I hit this pass at a nice speed, keep momentum up and have a clear road ahead of me, I climb it easily without any effort. The problem arises if I get slower traffic in front of me. The auto then changes up and down constantly.

When I get to the hilly section, the same thing happens. Constant momentum, and I am fine. The minute I slow down, it becomes a case of constant changing, which I assume is between 3rd and over drive.

Would it be better in this situtation to have the O/D off? Will I cause any unneccesary wear and tear if I switch the O/D on and off ?

sleeve84028 · **Posted:** Tue Apr 03, 2007 9:18 am

If you run into the issue where the automatic transmission starts "searching" for the proper gear it is a good idea to turn off the O/D function and just ride up the hills at a higher RPM...

DarbyWalters · **Posted:** Tue Apr 03, 2007 9:39 am

Just don't depress the button unless your tranny is constantly "searching" for a gear ... usually while towing or possibly climbing steep hills.

Albert · **Posted:** Tue Apr 03, 2007 10:00 am

sleeve84028 wrote:

If you run into the issue where the automatic transmission starts "searching" for the proper gear it is a good idea to turn off the O/D function and just ride up the hills at a higher RPM...

Correct. If driving mountain roads, and you happen to be close to the shifting point between D and OD (45-50 mph hour range with mine) push the button and lock out OD. This will kick up your rpm's and keep your motor higher in the power band (easier on motor and tranny), and keeps the tranny from continually shifting back and forth between D and OD. When your tranny continually shifts back and forth like that it builds up more heat. It gets HOT fast and heat eventually destroys tranny's if it can't cool itself quickly enough. The tranny cooler helps and that's if you have the tow package, you have one. (I am not sure if they come with a tranny cooler if you don't have the tow package). It would help weather you were towing or not. Also there is supposed to be a trans/hot idiot light that should come on if it ever did get too hot. Once you get back to flatter ground, push the button again and let it go back to O/D. Your tranny will thank you.

Over drive question

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