rumble strip feeling/noise only in A4WD

[jprix82]

98 expy,5.4

I have a intermittent vibration and noise in the front end that is very similar to running over rumble strips on the highway.It only lasts 2-3 seconds and i can feel it in the steering wheel and wants to pull to one side.
It only happens when im in A4wd and seems to only happen on the highway.

Cv joints,ball joints,tie rods has no play,any ideas?

 

[toms89]

The 98 4wd expeditions have a "center axle disconnect" which disconnects the passenger side axle when in 2wd. In A4wd, 4hi and 4low the passenger side axle is engaged.

Not sure why engaging it is creating the issue unless the center axle disconnect itself is having issues or its possibly stuck in 4wd.

 

[toms89]

By disconnecting the passenger side axle it effectively disengages the front drivetrain from the transfer case. With the open differential it allows the carrier case to spin freely. I believe the ideal was less parasitic drag but they did away with it (center axle disconnect) sometime in 1999.

 

[jprix82]

The 98 4wd expeditions have a "center axle disconnect" which disconnects the passenger side axle when in 2wd. In A4wd, 4hi and 4low the passenger side axle is engaged.

Not sure why engaging it is creating the issue unless the center axle disconnect itself is having issues or its possibly stuck in 4wd.

Is it possible the IWE solenoids can be going bad and causing the axle to make the noise?

 

[toms89]

Is it possible the IWE solenoids can be going bad and causing the axle to make the noise?

No IWE's on a 98. Only center axle disconnect.

 

[jprix82]

No IWE's on a 98. Only center axle disconnect.

Sorry i may have called them by the wrong name but i was talking about these..
Dorman/4WD Hub Locking Solenoid (600-401) | 1998 Ford Expedition 4WD 8 Cylinders L 5.4L EFI | AutoZone.com

I have 2 of them on the pass side firewall.

 

[jprix82]

any ideas?

 

[tonydiv]

If those go bad then the center axle disconnect won't engage or disengage. So you would either not have any power to the front or the front drive line would always be turning. (you'd notice the lower mpgs)

On mine the actual disconnect lever became stuck. It's a steel rod going through an aluminum housing, so it has a tendency to bind up. There is also a vacuum actuator that moves that lever, it can go bad also.

You need to see if the front tires and the driveshaft are both spinning when you put it in 4WD and do a 'burnout'. Snowy driveways are good for this. If the driveshaft is spinning , but the tires aren't, then there is something wrong with that center axle disconnect system.

If you use 4wd or awd quite a bit, then you may want to install a 4x4 Posi-lok cable that takes the place of those actuators. You manually lock and unlock the center axle disconnect.

 

[jprix82]

So after a good snow storm I was able to drive the truck in 4hi and noticed something.
There is a humming noise at low speed that seems to come from the left front side. The noise is similar to a bad wheel bearing.

If the wheel bearing was bad I should hear it regardless of the 4wd setting correct?

Also if the cv axle was making the noise I should hear it in a4wd because the axle is locked correct? I only hear the hum in 4hi

 

[tonydiv]

When you floor it in the snow in 4 hi, are the front tires spinning?

 

[jprix82]

Yep they spin.

 

[jprix82]

So i replaced the front driver side wheel bearing(seems to pulll left when noise happens) and swapped the cv axle with a known good one and the problem still exists.

Is there a bearing inside the diff that would cause this? Could the front axle locking actuator cause this? how would i check it and the vacuum setup?

If it matters the noise only happens at highway speeds(70-80mph)

 

[tonydiv]

When was the last time that the front diff fluid was changed? Those spider gears turn all the time and the fluid will get dirty even if you never use 4wd.

 

[jprix82]

I also changed it when I did the wheel bearing.

 

[jprix82]

Heres an update guys.I went to remove the front driveshaft(PITA) and noticed the ujoint on the transfercase side was bad.So i replaced both of them and took it for a drive and i still have the same problem.

So now im thinking either the shift fork inside the diff is worn and or the front axle bearings is bad.Im gonna check the shift fork first.

Does anybody have tips on replacing the axle bearings? And can i just remove the pass side axle tube without dropping the entire diff?

Side notes:
When i changed the cv axle i noticed the diff axles(that the cv bolts to) had a decent amount of in and out play[not sure if thats normal].
I switched it to 4H just to test and noticed alot of noise and vibration[not sure it thats normal because it was dry pavement]
When i switched it back to 2H the front diff did not unlock,but it was working fine when i was R&R the front driveshaft.