4WD not engaging
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4WD not engaging
I've had my Excursion for about 8 months and just discovered the 4WD is not engaging. I was in mud yesterday with the rear tires spinning so I switched to 4WD and heard the sound like it was engaging but then the rear wheels were still spinning but not the front. What is going on here?
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Engage the 4wd off road. Turn on your a/c. If the air blows out of the defroster vs. the dash vents you have a vacuum leak. I found my leak on a $4.00 vacuum hose cracked going to the wheel. (I assume you have the ASOF) system with auto hubs. Jim
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From: Wyandotte, Michigan
Did you rotate the hubs to lock and then try it? I converted mine back to auto/lock hubs after a 5 year stint with free/lock hubs. Took a bit of work to get the auto system working but it still is not 100%. I am losing vaccuum in the hub itself. I put new hubs and o rings on but still leaking somewhere in there.
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It could be the actuator. Mine went in the first 15K miles of owning my truck. This past winter I am not sure what is wrong but once again no 4x4 using the switch. I can lock the hubs from the outside and rip through everything then. I only use 4x4 when offroading anyway and I would not trust the switch . It would suck to be out and about in the mud and then the switch doesn;t work. Then Iwould have to get out and lock the hubs manually and get my feet convered in mud.
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From: Washington State
You really need to determine if it is a hub problem or a transfer case problem.
I have a way to test both but one is a bit involved. Not too bad but you'll be disconnecting wires and stuff. Still want to do it?
I have a way to test both but one is a bit involved. Not too bad but you'll be disconnecting wires and stuff. Still want to do it?
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Originally Posted by Downriver Thunder
Did you rotate the hubs to lock and then try it? I converted mine back to auto/lock hubs after a 5 year stint with free/lock hubs. Took a bit of work to get the auto system working but it still is not 100%. I am losing vaccuum in the hub itself. I put new hubs and o rings on but still leaking somewhere in there.
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Originally Posted by vettdvr
Engage the 4wd off road. Turn on your a/c. If the air blows out of the defroster vs. the dash vents you have a vacuum leak. I found my leak on a $4.00 vacuum hose cracked going to the wheel. (I assume you have the ASOF) system with auto hubs. Jim
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Originally Posted by njstevens
It could be the actuator. Mine went in the first 15K miles of owning my truck. This past winter I am not sure what is wrong but once again no 4x4 using the switch. I can lock the hubs from the outside and rip through everything then. I only use 4x4 when offroading anyway and I would not trust the switch . It would suck to be out and about in the mud and then the switch doesn;t work. Then Iwould have to get out and lock the hubs manually and get my feet convered in mud.
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Originally Posted by Monsta
You really need to determine if it is a hub problem or a transfer case problem.
I have a way to test both but one is a bit involved. Not too bad but you'll be disconnecting wires and stuff. Still want to do it?
I have a way to test both but one is a bit involved. Not too bad but you'll be disconnecting wires and stuff. Still want to do it?
Thanks.
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Originally Posted by wreakhavoc
If it was a bad actuator would you still hear the sound down there when you switch the dial?
If you select 4wd HI or Low you might hear the electronic shift, but if your vacuum lines to the wheel hubs are damaged your hubs won't engage. If you select manual on the hubs and have 4wd you probably have a vacuum leak. There is a line from the chassy to the wheel that can easily break and prevent the 4wd from working. This is why I suggest to turn your a/c on and select 4wd. If there is a vacuum leak your a/c will only blow out of the defoger and not the dash vents. A quick easy check to see if you have a vacuum problem. So summary,, if you do the a/c check and don't have 4wd,, go outside and select manual on the hubs,, should be a clockwise turn about 60 degrees on the selector, if you have 4wd then you just have a vacuum leak which should be an easy cheap fix. Jim
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Originally Posted by vettdvr
If ASOF is Automatic shift on the fly,, which you have by your selector switch.
If you select 4wd HI or Low you might hear the electronic shift, but if your vacuum lines to the wheel hubs are damaged your hubs won't engage. If you select manual on the hubs and have 4wd you probably have a vacuum leak. There is a line from the chassy to the wheel that can easily break and prevent the 4wd from working. This is why I suggest to turn your a/c on and select 4wd. If there is a vacuum leak your a/c will only blow out of the defoger and not the dash vents. A quick easy check to see if you have a vacuum problem. So summary,, if you do the a/c check and don't have 4wd,, go outside and select manual on the hubs,, should be a clockwise turn about 60 degrees on the selector, if you have 4wd then you just have a vacuum leak which should be an easy cheap fix. Jim
If you select 4wd HI or Low you might hear the electronic shift, but if your vacuum lines to the wheel hubs are damaged your hubs won't engage. If you select manual on the hubs and have 4wd you probably have a vacuum leak. There is a line from the chassy to the wheel that can easily break and prevent the 4wd from working. This is why I suggest to turn your a/c on and select 4wd. If there is a vacuum leak your a/c will only blow out of the defoger and not the dash vents. A quick easy check to see if you have a vacuum problem. So summary,, if you do the a/c check and don't have 4wd,, go outside and select manual on the hubs,, should be a clockwise turn about 60 degrees on the selector, if you have 4wd then you just have a vacuum leak which should be an easy cheap fix. Jim
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Originally Posted by njstevens
It could be the actuator. Mine went in the first 15K miles of owning my truck. This past winter I am not sure what is wrong but once again no 4x4 using the switch. I can lock the hubs from the outside and rip through everything then. I only use 4x4 when offroading anyway and I would not trust the switch . It would suck to be out and about in the mud and then the switch doesn;t work. Then Iwould have to get out and lock the hubs manually and get my feet convered in mud.
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you might select 4wd then pull the vac hose at the wheel to see if there is a vacuum. Key must be on. If there is no vacuum or weak you might have a vacuum leak. After doing this since you probably have the wheels jacked up, switch the hubs to manual and see if they lock up. If your wheels lock up to the differential in manual then you have a vacuum leak in a hub. Could be defective hub diaphragm.
IF turning the wheels in park lock the system up then the system is in 4wd and locked up through the transfer case. If the wheels are locked and the drive shaft to the transfer case turns but freely and the truck is in park,, then look at the actuator. They can be found on ebay pretty reasonable.
Note,, to get 4wd Low you must be in neutral foot on brake. Jim
IF turning the wheels in park lock the system up then the system is in 4wd and locked up through the transfer case. If the wheels are locked and the drive shaft to the transfer case turns but freely and the truck is in park,, then look at the actuator. They can be found on ebay pretty reasonable.
Note,, to get 4wd Low you must be in neutral foot on brake. Jim
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Originally Posted by vettdvr
you might select 4wd then pull the vac hose at the wheel to see if there is a vacuum. Key must be on. If there is no vacuum or weak you might have a vacuum leak. After doing this since you probably have the wheels jacked up, switch the hubs to manual and see if they lock up. If your wheels lock up to the differential in manual then you have a vacuum leak in a hub. Could be defective hub diaphragm.
IF turning the wheels in park lock the system up then the system is in 4wd and locked up through the transfer case. If the wheels are locked and the drive shaft to the transfer case turns but freely and the truck is in park,, then look at the actuator. They can be found on ebay pretty reasonable.
Note,, to get 4wd Low you must be in neutral foot on brake. Jim
IF turning the wheels in park lock the system up then the system is in 4wd and locked up through the transfer case. If the wheels are locked and the drive shaft to the transfer case turns but freely and the truck is in park,, then look at the actuator. They can be found on ebay pretty reasonable.
Note,, to get 4wd Low you must be in neutral foot on brake. Jim
Thanks to all who replied and please excuse my ignorance!
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From: WARRINGTON, PA
4wd noisy-clunking
ok after reading all of this, i now have a question on the system. my 4wd will lock up and the front wheels will drive the truck. but about 2 weeks ago, i went to pull into the driveway, and i heard what sounded like a bad u-joint in the front stub shaft. the switch is in 2wd, the hubs are in the free position. when i rotated the wheel, i noticed that the front axle would turn too. it did it on both wheels. it will not make the sound in reverse. and its only when i have the wheel turned all the way. i was thinking it was bad hubs. i checked and the u-joints are only $30/pair. any suggestions?? thanks...