Will not go into overdrive - Cars & Trucks

I have never known an overdrive that cannot be switched on or off at will or engaged or disengaged.

There are two definitions of overdrive and in the philosophy of some people the fifth gear is an overdrive.
The conventional manual gearbox, because the first motion shaft is locked to the third motion shaft in the top gear ratio, any supplemental ratio that has a ratio higher than 1:1 is considered an overdrive ratio.

The more traditional definition of an overdrive is a supplementary gearbox that can be incorporated into a normal manual gearbox to provide a single overdrive ratio for the purpose of quieter and more economical cruising.
The early overdrive was cable operated by a large chrome-plated dashboard-mounted handle. Later overdrives were hydraulic units that could be switched in or out by electricity, often by the means of a steering column-mounted switch or by a tiny switch incorporated into the gearknob.

A typical installation included an inhibitor switch mounted on the gearbox which prevented overdrive operation in the lower ratios when the benefits would be dubious.
Sometimes a lower than standard final drive ratio would be used and the overdrive ratios which typically could be selected whenever third or fourth gear was selected could be used together to produce something like a six speed close ratio gearbox which was hitherto unheard of when some of the rest of the world was still using "three on the tree" type three-speed gearboxes.

Most manufacturers had dispensed with overdrives by the end of the 1970's due to the weight and added expense, in favour of the now common five-speed gearbox, though Nissan incorporated an overdrive ratio into their automatic transmissions to compensate for torque converter slip when fuel costs began to rise disproportionately.

If you have an overdrive unit fitted to your car that doesn't work, I advise starting the diagnostic process by checking through the electric circuitry, wiring, switches and solenoid.

Hi EVE , I would suggest you take it to a reputable ASE Certified repair shop ! Do you know what transmission you have there are three different ones for your vehicle along with three different engine possibility's ! It could be the switch or a solenoid in side the transmission or a wiring problem or even a control module problem !

OVERDRIVE OFF SWITCH

DESCRIPTION The overdrive OFF (control) switch is located in the shift lever arm.
OPERATION The switch is a momentary contact device that signals the PCM to toggle current status of the overdrive function. At key-on, overdrive operation is allowed. Pressing the switch once causes the overdrive OFF mode to be entered and the overdrive OFF switch lamp to be illuminated. Pressing the switch a second time causes normal overdrive operation to be restored and the overdrive lamp to be turned off. The overdrive OFF mode defaults to ON after the ignition switch is cycled OFF and ON. The normal position for the control switch is the ON position. The switch must be in this position to energize the solenoid and allow a 3-4 upshift. The control switch indicator light illuminates only when the overdrive switch is turned to the OFF position, or when illuminated by the transmission control module.

OVERDRIVE ELECTRICAL CONTROLS

The overdrive off switch, valve body solenoid, case connectors and related wiring can all be tested with a 12 volt test lamp or a volt/ohmmeter. Check continuity of each component when diagnosis indicates this is necessary. Refer to Group 8W, Wiring Diagrams, for component locations and circuit information.
Switch and solenoid continuity should be checked whenever the transmission fails to shift into fourth gear range.

That is the transmission overdrive indicator light. On the left side of the gear-shift handle, you'll see a small button marked "O/D." This is the button used to toggle between "Overdrive On" and "Overdrive Off." Push the button to turn on the overdrive. If overdrive was already on, pushing the button turns it off.

Read more: http://www.ehow.com/how_7458292_turn-kia-sedona-overdrive-system.html#ixzz2zXYyipOZ

First, change your transmission fluid and filter while the engine and tranny are hot(to get out particles that may be jamming the overdrive gear)! Next, check to see if the overdrive motor is running when you flip it to overdrive. If not...change the overdrive motor.

The D inside of an O is for overdrive. It is an automatic overdrive transmission. There isn't an overdrive button on it. If you want to disable the overdrive you have to shift down a gear.

look in the overdrive cable see if its atatched and working if theres no overdrive cable if the overdrive sensor light is on than it could be an overdrive sensor.

try checking the bulb first

4R100 or 4R70W?

Geartrain
Power is transmitted from the torque converter to the geartrain components through the input shaft and forward clutch cylinder.

• By holding or driving certain members of the gearset, four forward ratios and one reverse ratio are obtained and transmitted to the output shaft. The ratios are as follows:

GEAR RATIO 1ST 2.71 to 1 2ND 1.54 to 1 3RD 1.00 to 1 4TH 0.71 to 1 REVERSE 2.18 to 1
Input Shaft
The input shaft is supported by two bushings in the stator support. End positioning of the input shaft is controlled by the splines in the converter turbine and the overdrive planet assembly.
Output Shaft
The output shaft is supported by two bushings in the case and by the slip-yoke and bushing in the extension housing. End positioning is controlled by the parking pawl gear and snap ring or shoulder and by the reverse ring gear hub and snap ring.
Overdrive System
The overdrive planetary system consists of the overdrive planet assembly, overdrive sun gear, overdrive ring gear, coast clutch cylinder, overdrive one-way clutch assembly and the center shaft, as shown in the following illustration. The overdrive planet assembly is splined to the input shaft. The overdrive sun gear is centered by a bushing on the input shaft and held in place laterally by needle bearings on the reactor support and the overdrive planet assembly. The overdrive sun gear is splined to the coast clutch cylinder, which in turn is splined to the overdrive one-way clutch inner race.
The outer race of the one-way clutch is splined to the overdrive ring gear, which is splined to the center shaft. The center shaft is centered by the forward planetary assembly and is laterally held by needle bearings on the center support and the overdrive planet assembly. The center shaft is splined into the forward clutch cylinder.
Two friction clutches are assembled in the overdrive planet assembly. The coast clutch is splined between the coast clutch cylinder and the overdrive ring gear. The coast clutch is activated to perform engine braking in MANUAL 1, MANUAL 2 and third gear with the transmission control switch engaged.
The overdrive clutch is splined between the case and the coast clutch cylinder. The overdrive clutch holds the coast clutch cylinder and, in turn, the overdrive sun gear, to permit the planet assembly to overdrive the ring gear.
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Forward Drive System
The forward drive system consists of the forward clutch cylinder, intermediate brake drum, intermediate one-way clutch, input shell, forward ring gear, forward ring gear hub, forward/reverse sun gear and the forward planetary carrier and forward planetary gears.
The forward clutch cylinder is splined on the center shaft. The forward ring gear is piloted on the forward ring gear hub. Thrust bearings on the forward planet assembly and forward clutch cylinder hold the forward ring gear hub in place.
The intermediate brake drum is radially supported by bushings on the center support and is laterally controlled by thrust washers on the forward clutch cylinder and center support. The intermediate brake drum has the inner race of the intermediate one-way clutch press-fitted on its pilot. The intermediate one-way clutch's outer race is splined to the intermediate friction clutch, which is splined to the case. The intermediate brake drum has lugs that are slotted into the input shell to form a mechanical connection. The input shell is splined into the forward/reverse sun gear. The forward/reverse sun gear is common to two planetary gearsets. The forward planet is splined to the output shaft and is laterally positioned by needle bearings on the sun gear and on the forward clutch cylinder, as shown in the following illustration.
Two friction clutch assemblies, the direct clutch and the forward clutch, are shown with the forward planetary assembly. The direct clutch assembly splines the forward clutch cylinder to the intermediate brake drum. The forward clutch assembly splines the forward clutch cylinder to the forward ring gear. The forward clutch is activated during all forward gears. While in third or fourth gear, both the direct and forward clutches are applied to hold the forward planetary assembly and enable it to act as a solid shaft.
In second gear, the intermediate clutch assembly holds the forward/reverse sun gears. It is applied, along with the intermediate one-way clutch, to hold the intermediate brake drum, input shell and forward/reverse sun gear. In higher gears, the one-way clutch overruns.
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Low and Reverse Drive System
The reverse planetary assembly consists of the reverse planetary carrier, reverse planet gears, the reverse ring gear, the reverse ring gear hub, the reverse clutch hub and the low-reverse one-way clutch assembly.
The reverse ring gear hub is splined to the output shaft and to the reverse ring gear. The reverse ring gear hub is laterally held by a needle bearing on the inner race of the low-reverse one-way clutch and a snap ring on the output shaft. The reverse planet assembly is splined to the low-reverse clutch hub. The low-reverse clutch hub is connected by the reverse clutch to the case. The inner race of the one-way clutch is bolted to the case.
The reverse clutch assembly is activated in REVERSE gear and in MANUAL 1. The reverse clutch bypasses the reverse one-way clutch during coast and MANUAL 1. The reverse clutch holds the reverse planet assembly in REVERSE gear to enable the sun gear to drive the reverse ring gear in the opposite direction.
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Apply Components
The following information describes the operation of the three 4R100 one-way clutches.
One-Way Clutch—Overdrive
The overdrive one-way clutch, shown in the following illustration, transmits engine torque from the overdrive sun gear to the overdrive ring gear in first, second and third gear range. The overdrive one-way clutch transmits power when the sprags are engaged between the inner and outer races. The inner race is splined to the coast clutch cylinder, which in turn is splined to the overdrive sun gear. The outer race is splined to the overdrive ring gear.
The overdrive one-way clutch engages whenever the overdrive planetary system attempts to drive the overdrive sun gear clockwise when the overdrive ring gear has a counterclockwise torque from the vehicle. When torqued counterclockwise, the overdrive one-way clutch engages and acts as a wedge to lock the sun gear and the ring gear together. During coast, the overdrive one-way clutch enables the ring gear to overrun or spin at a faster rate than the sun gear.
The overdrive one-way clutch overruns when in overdrive (fourth gear). In overdrive, the coast clutch cylinder is held by the overdrive one-way clutch, which in turn holds the overdrive sun gear. This causes the overdrive planet assembly to walk around the sun gear and overdrive the overdrive ring gear. The inner race of the overdrive one-way clutch is thus held stationary while the outer race is allowed to overrun clockwise.
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from the car manual:

Tum the overdrive switch on for good fuel
economy and smooth driving. If engine braking
is needed in the "D" range or if repeated
upshifting and downshifting between the 3rd
and 4th gear is needed when climbing a
gentle slope, it is recommended that the
overdrive switch be tumed off. Tum the
overdrive switch back on immediately afterward.

When the overdrive switch is tumed on, the
transaxle will automatically upshift to the second,
third and overdrive gears. When the overdrive
switch is tumed off, the transaxle will not
upshift to the overdrive gear. For normal driving,
the selector lever should be left in the "D"
position and the overdrive switch tumed on.
If you need to accelerate rapidly, press the
accelerator pedal all the way to the floor. The
transaxle will automatically shift to a lower gear,
depending on the vehicle speed and load.