4x4 won't engage
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Trailering
Joined: Oct 2021
Posts: 21
Likes: 1
4x4 won't engage
I see the 4x4 light come on when I start the truck but when I switch to 4x4 while standing still, I can hear the relay try to engage, and does so several times. But the 4x4 doesn't light up on the dash..
04 F350 6.0l Power Stroke Super Duty Crew Cab
04 F350 6.0l Power Stroke Super Duty Crew Cab
Last edited by Joshin; Oct 25, 2021 at 03:08 PM.
Logistics Pro
Joined: Jan 2010
Posts: 4,100
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Do you still have the 'auto/lock' hubs, or have you converted to manual hubs? Possible vacuum leak at the hubs but I would think the transfer case would still switch to 4WD.
Possible that the servo has gone bad, saw this once on a GM product but it's an electrical component, it could happen on anything.
Also possible that the truck needs to move slightly while shifting to allow the drivetrain to mesh properly. I would try this first before replacing parts.
Possible that the servo has gone bad, saw this once on a GM product but it's an electrical component, it could happen on anything.
Also possible that the truck needs to move slightly while shifting to allow the drivetrain to mesh properly. I would try this first before replacing parts.
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
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From: Stephensville WI
Check for voltage at the plug when you shift to 4H. If it's there, you most likely have a bad shift motor. If it isn't, then you get to follow the harness back until you find the issue.
Fleet Mechanic
Joined: Sep 2006
Posts: 1,491
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From: Fresno, CA
If I recall correctly the 4x4 light will illuminate once the Transfer case shifts into 4x4. There's a sensor that is used to "prove" the shift, once it's proven the light turns on. That's why you typically see a delay from when you turn the switch and see the light illuminate.
There is no feedback on the vacuum hubs. Easiest way to check those is engage 4x4, drive forward a few feet to engage the hubs and reach down behind the front wheel and see if the shafts are locked.
There is no feedback on the vacuum hubs. Easiest way to check those is engage 4x4, drive forward a few feet to engage the hubs and reach down behind the front wheel and see if the shafts are locked.
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Logistics Pro
Joined: Jan 2010
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The front hubs would be manually engaged through the center of the front rims. If they put the center caps on over those, then you'll need to remove the center caps. Hopefully they simply snap on from the outside, otherwise you'll need to pull the tire and remove the center cap to access the hubs.
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Trailering
Joined: Oct 2021
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Thank you everyone for your responses. I was able to mess with it some more today and found that I can switch into 4wd H but there is a loud 'clunk' when it does. Sounds like when you miss a gear. Is that normal? The 4x4 light does indeed come on though, I have to be going at least 15mph for it to engage.
Thread Starter
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Trailering
Joined: Oct 2021
Posts: 21
Likes: 1
The front hubs would be manually engaged through the center of the front rims. If they put the center caps on over those, then you'll need to remove the center caps. Hopefully they simply snap on from the outside, otherwise you'll need to pull the tire and remove the center cap to access the hubs.
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