Question about 2003 Ford F250 Super Duty Crew Cab

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Shift on fly not working

My 03 f-250 7.3 liter will not switch to 4x4 auto, I have to manually lock the hubs and they have gotten very tight. I sucpect vacuum issue but not sure

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This has happened a couple of times on my truck. I have had a couple of vacum lines replaced. The lines were chewed thru by mice. After repair hubs lock and unlunk just fine.

Posted on Jul 31, 2008

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Most likely vacuum problem. Does the A/C blow out of the correct location? i.e if you have it set to vent does it blow out of the vents? If not, then you have a vacuum leak somewhere. The vacuum lines to the autolock hubs is a common problem.

Posted on Jun 23, 2008


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2003 ford f250 superduty 4x4 don't work no indicator light on dash changed4x4 switch module what next?

Check for codes. Usually part stores do it for free. here is how it works.
Principles of Operation

Electronic Shift on the Fly (ESOF) System

The electronic shift on the fly (ESOF) system is an electronic shift system that allows the operator to choose between 2 different 4x4 modes as well as 2-wheel drive. The operator can switch between 2H and 4H mode at speeds up to 88 km/h (55 mph). To engage or disengage 4L, the 4x4 generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal depressed and the transmission in NEUTRAL (or clutch pedal applied on manual transmission vehicles). This system contains pulse vacuum hublocks (PVH). The selector on the hublock, when turned fully counterclockwise to the AUTO position, engages/disengages the hub depending on the driver-selected 4x4 mode of operation. The hublocks also contain a manual override. When the selector is rotated fully clockwise to the LOCK position, the 4x4 vacuum and electronic system used for coupling the front axle to the wheel is bypassed.

The transfer case is equipped with a dual-cone synchronous clutch. This clutch is used to synchronize the front driveline to the rear. All other internals operate in the same manner as the manual shift system. When the mode select switch (MSS) on the instrument panel is turned, the 4x4 module powers the transfer case motor, which activates a shift fork and engages the clutch. When the shift motor reaches the desired position, as determined by the encoder position inputs to the 4x4 module, power to the shift motor is removed. When the transfer case front and rear output shafts are synchronized, the lockup collar mechanically engages the mainshaft hub to the drive sprocket. At this point, the front axle PVHs are engaged. Instrument cluster "4x4" and "Low Range" indicator operation is controlled via hardwired outputs from the 4x4 module.

Electronic Shift Transfer Case

The New Venture Gear NV 273 electronic shift transfer case is a 3-piece aluminium design. The unit transfers engine power from the transmission to the front and rear axles. Under normal driving conditions the unit is in 2-wheel drive high (2H), but when desired, the operator may shift into 4-wheel drive high (4H) or 4-wheel drive low (4L). The transfer case is shifted electronically. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the mainshaft.

The encoder assembly used for mode indication is of a Hall-Effect type. The system uses a total of 4 independent transistors for mode recognition. Each transistor is associated with a specific range of motor movement. When the circuit to each transistor is closed, a ground path to any of the A, B, C or D encoder pins is accomplished. When the circuit to each transistor is open, the connection to any of the A, B, C, or D encoder pins is pulled to voltage. Mode indication is "decoded" by the 4x4 module based on the varying combinations of signals coming from the transistors.

Hublock Operation

With the hublocks in the Auto position, the 4x4 ESOP system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4x4 modes. A high vacuum level (222 mm or 8.75 in. Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum level (114 to 184 mm or 5.9 to 7.1 in. Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD mode. The vacuum signals are supplied to the hublocks by system components, including the 4WD control module or GEM, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring connections, loose vacuum connections or damaged vacuum lines.

Dec 12, 2014 | 2003 Ford F250

1 Answer

Transmission was replaced and now have no shift..neutralized

Understanding how a machine works--whether a car, toaster or computer--is crucial to obtaining a clear understanding of what the trouble spots might be and knowing how to identify them. The Internet is the fastest, most up to date, and cheapest way to get a quick refresher course (or even learn for the first time) how your car works. The animated How Cars Work feature at is excellent; it allows you to separately look at each system of the car, from the brakes to the engine to the drivetrain, and briefly explains each animated sequence. Before you begin searching for the cause of your Ford Ranger troubles, make sure you look at this or a similar site first to brush up on your car knowledge.
Next, recruit a friend, spouse or other helping hand and head out to the car to begin diagnosing the problem. Determine if the 4X4 system can be shifted to 4X4 high by pressing the 4X4 button. The dash and 4X4 buttons should light up. If they do not, one of the following is faulty: the dash button, the 4X4 module or the shift motor.

To determine which of these three is malfunctioning, have your friend sit near the module. Press the 4X4 button and ask your friend to listen for the sound of the relays in the 4X4 module. If the relays can be heard, the problem with the 4X4 lies in the 4X4 module computer or the shift motor. The most common problem in this case is a broken stop bumper in the shift motor. If your friend is unable to hear the relays within the 4X4 module, you will need to make sure the 4X4 module is functioning properly.

To check the 4X4 module, unplug the two connectors that are plugged into the left side of the module. Turn the car on and push the reset/test button located on the module. After pushing the button, the LED light located on the module should flash rapidly four or five times. If the LED lights do not flash or flash without stopping, the module is damaged. If the LED lights flashed, then stopped after four or five times, the module is functioning properly and you will need to check other parts such as the shift motor, magnetic clutch, wiring harness and 4X4 switch to determine the cause of the problem.

If your 4X4 is making a grating or clicking noise from beneath the front wheels, the hubs need to be checked to make sure they are locking properly. To test this on a car with automatic hubs, rotate the front axle shafts under the truck. If, after a few turns, the axle locks up and can no longer be turned, the automatic hub is working properly. If, however, the axle does not lock up and you are able to continue rotating it, the hub is either bad or in need of a good cleaning.

To test a car with manual hubs, make sure the 4X4 is off and rotate the axle until it locks up. Again, if the axle does not lock up, the hub is not working or in need of a cleaning.
To determine if the automatic hub is no longer working, take the car out of 4X4 mode and rotate the axle shaft. If the axle does not lock up after a number of revolutions, the hub is most likely not working at all. Repeat this with the other axle shaft. On a car with manual hubs, disengage 4X4, lock in the hubs, and attempt to rotate the axle shafts. If they can be rotated at all, the hub is not working. Repeat this with the other axle shaft.

BMW Parts

May 25, 2012 | 1995 Chevrolet Blazer

1 Answer

4x4 K1500 Chevy Truck, 4 wheel drive repair instructions

There are a number of different hub systems so this may not work but it has worked for me on both auto and manual locking hubs. On a flat surface without traffic. Put the trans into neutral, shift the transfer case into 4x4, shift the trans into reverse and back the truck up 15-20 feet. Completely stop and shift trans into drive. See if this has locked the hubs in. If not, you can also try following the same instructions except shifting into 4wd low. Sometimes the hubs need a "bump" to get them to slip into place. Keep In mind that if the 4 wd low select works, you need to shift it back into 4 wd high before continuing! When taking the truck out of 4wd to 2wd, I recommend the same, shift to neutral, select 2wd, back truck up, shift back to drive and check. Its entirely possible that your hubs need maintenance (they're often overlooked) but hopefully this will get you going. Please let me know if thus worked or if I can offer other suggestions. Good luck!

Jan 18, 2012 | Chevrolet 1500 Cars & Trucks

1 Answer

1992 ford full size bronco xlt push button 4x4 auto locking hubs. I do not think 4x4 is working. yellow 4x4 high will come on will not go in low.

Junk the autolocking hubs for a set of good quality manual locking hubs. Your local auto parts store should have them in stock. E-Bay is a low-cost option but all premium hubs come with a warranty regarding failures and saving a couple bucks online is not worth it to me when I can warranty them at the local parts store. Get yourself a manual (Chilton or Haynes) and they will give you complete directions. As for the low range not working I found on my '92 that I had to pull the shift actuator motor off of the transfer case and re-apply the grease to the shaft as the old grease was stiff a non-pliable. It has not failed me since and I put it into low at least once a month to ensure that it works before bad weather hits.

Dec 25, 2010 | 1991 Ford Bronco

1 Answer

I bought a 2005 ford F150 (lariat) 4x4 used. It did not come with an owners manual. What is the procedure for putting it in four wheel drive?. There are no hub locks, its auto.

You can download a PDF of the owners manual from Ford

The shift on the fly ( Electronic with the switch on the dash or Mechanical with the lever ) is all you need to do. The hubs autolock once the truck is in 4WD. Check the page on the shift, 2WD into 4WD is 45 MPH ( think that is it ) or lower if the temp is 32* F or higher ( it is slower in colder weather ). Shifting into 4L is stop, place truck in Neutral or Park, then shift into 4L. Please verify in the manual, this is just what I recall reading.

Mar 04, 2010 | 2005 Ford F-150

1 Answer

I Have a 2005 ford excursion 4X4 The shift on the fly is not working. I have power at fuse/relay # 111 , it looks like i have no power at the switch and the light on the dash dose not light up. what...

I am having the same problem. But my lights work... My solution is manually lock your hubs in...Screw the Shift on The Fly.... After locking the hubs in I have power to the front wheels...My uncle spoke with a kid at his work who used to service vehicles and the shift on the fly seems to be a constant headache...He stated it does not always lock in and is just a pain in the *** cause there was not a thing wrong with it, it just does not always engage. And I have found this true while deer hunting...So I just walk out and lock them in manually...Just remember dry roads will and I say will eat up your tires.....Good luck!

Jan 29, 2010 | 2004 Ford Excursion

1 Answer

2003 ford crew cab 7.3 diesel some times the shift on the fly engages some time not what could be the problem.Thanks

If the light comes on and you feel the transfer case lock in then it might be a vaccuum line going to the steering knuckle. The hubs are locked in by vaccuum. Try locking the hubs in manually and see if there is any problem. If it works ok then there is a vaccuum problem. If not then there is either an electrical problem(if there is a switch for 4X4) or transfercase problem.

Dec 31, 2009 | 2003 Ford F350 Super Duty DRW SuperCab

1 Answer

My friend has jus bought a 1992 Pajero, 2.5 auto, swb, no manual with it. He has heard that when changing from 4x4 to 2wd that you need to stop the vehicle, go intp 2wd, then reverse for a couple of yards...

He need not stop to change from 4x4 hi to 2wd. He can also go from 2wd to 4x4 hi "on the fly" as long as the front hubs are locked, he is going straight and maintaining a steady speed. If the hubs are manually locking, he must exit the vehicle and lock the hubs. If they are automatic locking, in order to go from 2wd to 4x4 he must stop, put the vehicle in 4wd hi and pull off. Once he starts moving, the hubs will automatically lock, he can then switch from 2wd to 4wd hi and vice versa "on the fly". To unlock the hubs, he will need to stop, put the vehicle in 2wd and back up 3 ft. (remember, this is on automatic locking hub models). Hope this is helpful!

Nov 05, 2009 | 1993 Mitsubishi Montero

1 Answer

My 7.3 liter will not shift on the fly into 4X4 low. I can manually lock the hubs, the left manual hub is very hard to turn, and can't tell if it is in high or low as there are no marking on the hubs and...

hub locks are worn out, especially if you cant turn them. And its not high and low. Its either auto?lock for switch style shift, or free /lock for old style floor shift. also hub seals could be worn or vacuum system not working.

Apr 15, 2009 | 2003 Ford F250 Super Duty Crew Cab

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