overdrive usage

[Chris Castineira]

Quick question -- While drvong with 2 guys in the truck about 170 each and a payload of 1000 pound on primarily flat roads should i take the overdrive off. Thanks.

CHRIS

 

[Woppy V]

dont think u would even on hilly roads

 

[Richard L]

Probably not.

Turning the overdrive off is designed to prevent the transmission from hunting for a gear.



When you carry a heavy load or are trailering, and the transmission shifts into overdirve (5th gear) the engine may not be able to pull that load at highway speeds so it will downshift into 4th gear. When the vehicle gets up to speed it will shift into 5th gear again, and will start to slow down again, and the downshifting/upshifting will continue to repeat.



If you are carrying a load or towing and the transmission is not constantly hunting for 4th and 5th gear, there is no need to turn off the overdrive. Obvioulsy if you are starting up a long slight uphill, that may cause the transmission to start to hunt for the proper gear. you can turn the OD off until you get over the crest of the hill...That assumes that there are few hilss or uphill inclines.



Anytime you are heavly loaded and your transmission is constantly hunting for 4th and 5th gear, you should turn the OD off. If it's not hunting for 4th or 5th gear, then leave the OD off for slightly better gas mileage.



...Rich

 

[Gypsy me]

You do use it if you are climbing IF you feel the engine is sluggish or trying to dog out. (I'm not sure how to explain that...I just know how it feels when my trac has trouble climbing hills)



Check your owners manual it will explain when and how to use the OD off

 

[Richard L]

To make it a bit clearer. When you turn the OD off, your automatic transmission will never shift into 5th gear and just makes the transmission a 4-speed automatic.



It does not effect the operation or performance in any of the other 4 gears.



There for if the OD is On, and you are carring or towing a heavy load, 5th gear overdrive may not be able to maintain road speed and the transmission will automaticly downshift to 4th gear. Once your road speed increases, the transmission will shift back up into 5th gear and will start to slow down again and eventually it will downshift to 4th gear again, and that will continue until the OD is turned off or you are able to maintain the road speed in 5th gear. That constant shifting is often called "Hunting for gears" in automatic transmissions. It just means 4th gear is too low and 5th is too high.



Obviously, heavier loads, steaper hills and the rad speed you are attempting to maintain will determine how much gear hunting goes on.



...Rich

 

[Bill Kaiser]

Richard L,



Great way to explain that! I have 07 v8 with 6 speed transmission and it took me a long time to get used to the shifting even up a little hill at 65mph it downshifts same hill at 80mph no problem no downshift because it is a a high enough rpm to generate enough horse power to pull it. 6% grade hills start up them at about 80 downshifts once rightway then downshifts second time fairly quickly speed has dropped to 75 by now and it will not pull this hill in this gear; speed drops to 70 rpm is about 2500. Next downshift is extreme;rpm3200 speed is now 65 and climbing gets back up to 75mph and 3800rpm and shifts back to higher gear and repeats the cycle all over again, madening.



So if I have other traffic around I take it out of over drive and shoot up the mountains at 75 and 3500rpm, a little noisey, engine noise and exhaust noise are about the same with magnaflow exhaust. Just for fun I floored it to see what it would do; and at 95mph and 5200 I decided that was plenty of fun for one day. I was at the top of the mountain anyway by then.



Bill

 

[Dennis Shelley]

I have a 2001 ST. Every October I haul three guys and our stuff for a week plus a trailer with the hot aiar balloon from Iowa to New Mexico. More than 2,200 pounds of equipment and trailer. This is a 16 hour drive nonstop.. We drop the tranny into gear and let the ST figure out the best gear. We go from elevation of 990 MSl to 4,500 msl. Never touch the OD button. To date 121,000 miles W/O a problem of gear selection.

Life is easy, do'nt try to make it complex.

 

[Richard L]

Dennis,

It's not just the elevation or the weight, it's a combination of the speed you are trying to maintain vs the load on the engine which includes the weight and the steepness of the incline you are climing. Clime of 3500 feet in 16 hours is not necessarily steep.



I had my Sport Trac start hunting gears on a few steep slopes in Kentucky and it was just me and my wife and about 500 lbs in the bed and I had the cruise control set at 65-70 MPH.



Had you encountered a steep enough incline with that amount of weight or you were trying to pull as steeper incline at a higher speed ,you would have encountered the hear hunting.



...Rich