Realization that overdrive can be off...save fuel?

[Qxxx4]

What exactly IS overdrive, and if i switch it off, what does that mean...less performance? better fuel economy in city driving? or is it just dumb to have it off...especially if it gives me a yellow dashlight saying "OD OFF"

[bmlawless]

An oversimplified explanation is that it is another gear. Think of it as a fouth gear. Turning it off would be the same as driving a five speed manual without ever using the 5th gear. It is a good idea to leave it on and let the guys who engineed the transmission do their job.

The exception to this is when you are in an environment where you are constantly shifting back and forth between OD and D. The only time I turn mine off is when I am towing and climbing those subtle grades where you can't hold your speed without giving it gas, then you let off and it slows down, then you give it gas, etc. The constant shifting will heat up the transmission.

I will also use it when driving on curvy roads where the constant shifting starts getting annoying. In my dually, I will even go down into 3rd when climbing and towing.

[Qxxx4]

great explanation, it makes sense thanks!

[fueler]

Like bmlawless said, our 4th gear is considered "overdrive" and the button on the shifter turns it off (so 4th gear is not used) Another important thing the o/d off button does, is it actually locks up the torque converter from slipping. When driving around normally, it's actually slipping a lot of the time for better MPG and smoothness, at the cost of more heat. When doing things like towing or going uphill for a long time, if you dont use the OD feature then the transmission will do it with torque converter unlocked and creates A LOT of excessive heat (which kills transmissions)

You can do O/D off when going uphill, it will be higher RPM's than 4th gear but a lot less heat in your transmission which can be better.

Heres something you can try to feel what im talking about: Drive normally, through 1st, 2nd, and into 3rd gear. Give it some gas in 3rd gear so the RPMs go higher instead of normally switching to 4th. Try to make it not go into 4th gear (giving it more gas) This is easier to do uphill. Now hit the O/D off button. You will notice that the RPM's will drop by around 1k rpm - but youre still in 3rd gear!!! Thats the torque converter locking up. Press it again and watch the RPM's go right back up in 3rd gear.

Heres some info on the torque converter http://www.4x4parts.com/ubbthr...22180 And heres a quote from the Australian Pathfinder forum (PCOA) in regards to towing/uphill and o/d: Quote »Basically there is not really a one rule fits all circumstances, you should be in the right gear for the right situation however there are some things to keep in mind.

Towing in 4th gear is fine if the torque converter is locked up, if you find that towing in 4th unlocks the torque converter a lot or for extended periods it is best to tow in 3rd gear.

An ununlocked torque converter puts extra heat into the transmission and making sure the torque converter is locked as much as possible is more important. It is excess heat that kills auto transmissions.

The torque converter will lock in both 3rd and 4th gears you will find that with towing depending on the roads you will be in 4th torque converter unlocked. If that is the situation switch off overdrive and stay in 3rd locked converter, if you need a few extra revs more throttle will unlock the torque converter and then lock again fairly quickly.

All this is fine providing you tow a reasonable weight, if you want to tow 3 tonnes then you will probably have some problems. (clarify that point: 3 tonnes for any length of time.)

Cheers [/quote] Now get this, a few years ago I remember reading about a fellow R50 offroader who found the electronics that control this and was able to make a switch in his dash so he could manually lock up the torque converter, whenever he wanted, even in 4th gear. I think it was System-F on 4x4parts.com but i'm not sure - either way I couldn't find the writeup now. -FUELER

[martymcfly]

great read, question. you mentioned having OD off when towing or OD on??A bit confused....

[KoukiS14]

With the VG, it's handy to shut off for mountain driving I found. .

[Densetsu]

OD's meant for high-speed, low-load driving.

Any task that places a significant load on the Pathy (towing, mountain driving, hauling an entire offensive line around), it's best to leave OD off.

[Issac]

man I take it off all the time except freeway and downhill

[KoukiS14]

I turn it off for downhill (mountain driving) to hold my speed a bit better. Pretty much the only time I use it. . but due to this thread, I did drive around awhile yesterday with it off. I didn't like the extra noise

[ubpsanity]

I drive with mine on all the time, except for slowing, sometimes I'll use it to do some engine braking since it will lock up the torque convertor. Thats one of the things I hate about automatics, you lose all that engine braking.

Did anyone find out how to manually lock the convertor up?

[bmlawless]

The only time I turn my OD off is when I am going down long grades in my pickup with my camper. On my truck there are actually 4 position 1,2,3 and a "D" with a circle around it.

[02QX4ME]

Heres something you can try to feel what im talking about: Drive normally, through 1st, 2nd, and into 3rd gear. Give it some gas in 3rd gear so the RPMs go higher instead of normally switching to 4th. Try to make it not go into 4th gear (giving it more gas) This is easier to do uphill. Now hit the O/D off button. You will notice that the RPM's will drop by around 1k rpm - but youre still in 3rd gear!!! Thats the torque converter locking up. Press it again and watch the RPM's go right back up in 3rd gear. -FUELER

I thought torque converter locking up only happens in 4th gear.

[fueler]

only 3rd and 4th torque lockup does not happen in 1st or 2nd

[02QX4ME]

only 3rd and 4th torque lockup does not happen in 1st or 2nd

Thanks Fueler. I will try to feel it in 3rd gear.I could easily feel it in 4th gear, as well as seeing RPM drops. I never paid attention to it in 3rd gear, as normally I left OD on and it does not stay in 3 rd gear long...