4x4 weirdness
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Logistics Pro
Joined: Sep 2002
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From: Central KY
4x4 weirdness
Help me understand what's going on.
With truck off the ground, engine off, t-case in 2H, trans in park, the driver side wheel spins and spins the driveshaft with it. Passenger side is locked totally up. Wheel, CV, driveshaft will not spin.
With engine on and in park both sides spin freely. With engine on in park and t-case in 4H both sides are locked.
Turn engine back off and driver side wheel will spin by hand, passenger side is locked up tight and will not spin.
This seems odd.
With truck off the ground, engine off, t-case in 2H, trans in park, the driver side wheel spins and spins the driveshaft with it. Passenger side is locked totally up. Wheel, CV, driveshaft will not spin.
With engine on and in park both sides spin freely. With engine on in park and t-case in 4H both sides are locked.
Turn engine back off and driver side wheel will spin by hand, passenger side is locked up tight and will not spin.
This seems odd.
Cargo Master
Joined: Sep 2023
Posts: 2,822
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From: Virginia Beach
working as advertised. when engine off there is no vacuum to the IWE's (Intergraded Wheel Ends) which lock and unlock the hubs. you do not have a front locker so only 1 wheel works in 4WD. with the engine on making vacuum, it locks that wheel in 4WD.
Lead Driver
Joined: Jan 2019
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From: N.W. Alabama
This is on the home page really helpful-->Everything You Wanted To Know About The IWE System...And Then Some - Ford Truck Enthusiasts Forums
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Logistics Pro
Joined: Sep 2002
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From: Central KY
And what in the world do you do in the event that the truck is dead and you have to push it, or flat tow it?
Hotshot
Joined: Feb 2004
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From: The Shenandoah Valley
I think the driver side is maybe not locking as it should, maybe mud in it or a broke spring (that engages an IWE when there is no vacuum to pull it open), etc. Might be trash or other stoppage in the vacuum hose not letting it free to fully engage?
Just speculation, as trash in the vacuum line near the IWE might act like a check valve, not releasing all vacuum allowing the IWE to fully lock ... and that's all it is ... just speculating.
Just speculation, as trash in the vacuum line near the IWE might act like a check valve, not releasing all vacuum allowing the IWE to fully lock ... and that's all it is ... just speculating.
Last edited by tbear853; Oct 7, 2025 at 09:48 AM. Reason: explaining a thought
Cargo Master
Joined: Dec 2015
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When the engine is off, the IWEs are engaged. If the t-case is in 2wd, either wheel should spin -- it will simply force its CV axle to spin with it AND will cause EITHER the other CV to also spin OR the d/s to spin.
^^^ this is very important and how an open diff works -- 2 out of 3 will spin together.
NOW, if you're in 2wd, engine off and the pass side wheel is "locked up," something isn't right. There's no reason that side should not spin -- it will simply force its CV to rotate with it AND either the other wheel OR the d/s
If you're in 4wd, engine off: it should still spin but will require the OTHER wheel to also spin. The d/s is now fixed to the rear output BECAUSE YOU'RE IN 4WD so the front d/s canNOT move unless the whole truck moves.
All the above assumes you have BOTH front wheels elevated for testing.
Also be careful about what constitutes 4wd and 2wd. The truck must travel at least several feet not bound up to allow the front output fork time to release. You may be able to accomplish the same by wiggling the front d/s by hand with both front wheels elevated. Maybe.
As an aside, most diff lockers allow either side gear to spin FASTER than the pinion (driveshaft) but never SLOWER. This still allows for a level of differentiation in turns. Being 100% tied together is a spool or Lincoln Locker.
Last edited by WWR; Oct 7, 2025 at 03:14 PM.
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