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4x4 will not unlock at front axle will go into 2 wheel but the axle stays locked

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You did not specify what year it is. You need to know what controls the front diff-lock, is it vacuum or electronic? If it is vacuum then you need to inspect the system for vacuum leaks and/or faulty vacuum devices (switch on transfer case, diaphragm on front diff, etc). If it is electronic you need to have it checked for codes, and/or service the differential controls found in the front diff casting.

Posted on Sep 11, 2009

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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

I have a 1996 ford f-250 4x4 i have a shift in the floor but my wheels won't engage


ARE THE HUBS LOCKED IN FIRST? FOR YOU HAVE TO LOCK AND UNLOCK THOSE HUBS FROM THE OUTSIDE.. EACH TIME YOU GO INTO 4X4 AND WHEN YOU GO OUT OF 4X4 TO 2 WHEEL..DRIVE. OR YOU DON'T HAVE A FRONT DRIVE SHAFT GOING TO THE FRONT AXLE?? OR ITS BROKEN OR THE TRANSFER CASE IS BAD??

Feb 09, 2014 | 1986 Ford F 250

1 Answer

2002 jeep wont stay in 4wheel drive low


Your JEEP is only part time 4WHEEL DRIVE as you can't DRIVE on the STREET with it, its NORMAL and nothing is WRONG.


Part-Time and Full-Time 4x4 systems...

A part-time 4x4 system called Commandtrac is in all Wranglers together with low-end Cherokees and Liberties. A part-time 4x4 system locks the front and rear driveshafts together inside the transfer case so they drive the front and rear axles together in lock step. Because they are locked together, the front and rear tires must rotate at the exact same rpms. However, the front tires must rotate faster than the rear tires during any turn so a part-time system fights that... which makes a part-time system inappropriate on a paved road because the high level of traction on a paved road prevents the tires from slipping which would otherwise allow the front and rear tires to grudgingly rotate at different rpms. Offroad this is not a problem since the poor traction of an offroad trail allows the tires to slip as needed. But when they try to slip/rotate at different rpms on a high-traction surface, the entire drivetrain is stressed which is bad for it. This problem is called "wind-up".

In reality however, the front and rear axles really don't even turn exactly the same RPMs when you're in 4wd so you still get "wind-up" if you drove in 4wd on the street even if you drove in a perfectly straight line. Why? Because 1) you can't drive in a perfectly straight line and 2) the front and rear axle ratios are usually .01 different from each other. Like a 3.73 and 3.74, 4.10/4.11, etc.. Why the .01 ratio difference between the front and rear axles? Because the front and rear axles usually have different ring gear diameters which makes it nearly impossible for the gear manufacturers to economically make the front and rear axle ratios exactly the same. And no, they are not made .01 different on purpose to make the front or rear pull more when in 4wd, that is an old wive's tale.

Finally, a full-time 4x4 system like Selectrac is available on Grand Cherokees, Cherokees and Libertys couples the front and rear axles together, but they are not mechanically locked together like they are with a part-time 4wd system. The front-to-rear axle coupling can be done via either a differential like the Selectrac system uses (just just like what is in the center of an "open" axle) or a fluid (viscous) coupler. The benefit to a full-time 4wd system is that because the front and rear axles are not mechanically locked together, the front and rear tires/axles can rotate at different rpms from each other. This allows a vehicle with a full-time 4wd system to drive in 4wd "full time" on a paved road without problem since there is no 'wind-up' problem to harm the drivetrain. You cannot get a full-time 4x4 system in a Wrangler from the factory.



HOPE THIS HELPS.

Sep 08, 2012 | 2002 Jeep Wrangler

1 Answer

Ford explorer 2005 4x4 lite comes on brakes lockup then unlock for a few seconds then releases goes 100 yards and does it again. Put back to auto 4x4 and it will kick back in again


This is not the brakes locking up. it is the transfer case or front axle. I suggest that you leave it in two wheel drive or auto until you can have it looked at. Two wheel preferably.

Jul 19, 2011 | Ford Explorer Cars & Trucks

1 Answer

I own a 2007 dodge ram 1500 with the 5.7 hemi and automatic transmission, my auto 4x4 stays on and wont switch back to 2 wheel drive or 4x4 lock. ive only owned the truck for 2 weeks and its happened each...


The problem may be related to technical service bulletin TSB 03-001-07 which involves replacing the front axle actuator disconnect and a software update. You should be able to Google the TSB and look at the build date listed in the bulletin to determine if it applies to your vehicle.

Apr 18, 2011 | 2007 Dodge Ram 1500 Quad Cab Sport

3 Answers

4x4 front end not engaging


my computer problem is hard disk system found warantty hard disk

Feb 24, 2010 | 2006 Ford F-150

2 Answers

How do i kick the 4 wheel drive in on my 92 wrangler i kno u have to put the shifter in to 4 weel low or high but it doesnt kick in does anything else have to happen


the hubs on the front wheels have a lock, turn this in the direction indicated by the arrow to lock the hub. When your'e done with 4x4 unlock the hubs again, they may be hot after a harsh or long drive in 4x4 so be aware of this.

Jan 14, 2010 | 1992 Jeep Wrangler

1 Answer

Free-wheel lubrication on a 4x4 pick up


thanks a lot for your e-mail. I resolved the problem by "trial and error" I did ok. THANKS

Sep 09, 2008 | 2007 Nissan Frontier SE Crew Cab

3 Answers

Right Front Hub 2007 F350 DRW 4X4


check wheel bearings and axle joint at the end of the hub

Nov 30, 2017 | 2007 Ford F-350 Super Duty XLT

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