Wobble from x-fer case?

[White98]

I was talking to my local "former" ford tech the other day about the wobble/shimmy that I am experiencing with my '98 XLT. He says that when he drove it during inspection, he thought that the shimmy was coming from the transfer case? He said that it felt as if the x-fer case was trying to engage while driving which was causing the shimmy. He mentioned that there are speed sensors or something for the fromt and rear axles, and if one of them is out, it will call on the x-fer case to engage.
Does this sound right to anybody?
Would the "Brown wire mod" help alliviate this, if in fact, this is the problem?

 

[Opera House]

Have you changed the fluid lately? The can loose fluid without any sign and cause problems. Brown wire mod would prevent the clutch from engaging. The clutch is always slightly engaged. I wonder about the term wobble. The bearing mount for the rear output shaft can become egg shaped. This can be tested by securing movement of vehicle and placing the vehicle in neutral to remove forces on the shaft. Then check for up down movement at the flange.

 

[White98]

I suppose that the wobble is more of a shimmy. It seems to be more noticable when you apply heavy skinny pedal. It starts @ about 2500-2800 rpm after that it pretty much goes away. If you apply the skinny pedal lightly, it tends not to shimmy at all, or at least it is not noticable. I will need to check the bearings as you have suggested. I gave them the quick shake them to see if they move, but there was no noticable movement. And I did replace all of the u-joints so it rules them out. About changing the fluid, the x-fer case was apparently "serviced" before I bought the truck a few weeks ago. The guy I bought it from said that the dealer replaced the x-fer case chain. Perhaps whoever "fixed" F'd something up.
IS there anyway that I could completely shut down the 4x4 electrically? Like pull a fuse or something to see if infact the x-fer case IS trying to engage?

 

[IZwack]

IS there anyway that I could completely shut down the 4x4 electrically? Like pull a fuse or something to see if infact the x-fer case IS trying to engage?

Yes, you can disconnect the transfer case's electrical connectors (I think there are two of them). That will prevent the transfer case from switching to 4wd mode. You will see the 4HI/4LO lights blinking on the dashboard but thats no problem.

I suppose that the wobble is more of a shimmy. It seems to be more noticable when you apply heavy skinny pedal. It starts @ about 2500-2800 rpm after that it pretty much goes away.

This kinda sounds like a torque converter issue .. kinda

 

[White98]

IZwack. Thanks I will try and disconnect the wires from the t-case. I just wanted t make sure that by disconncting the wires, I was not disabling speed sensors and other "necessary" items.

As far as the "sounds like a torque converter issue...kinda" Kinda what? Like it is a t-convert isuue or... Can you elaborate please?

Thanks again for all who are helping.

 

[IZwack]

IZwack. Thanks I will try and disconnect the wires from the t-case. I just wanted t make sure that by disconncting the wires, I was not disabling speed sensors and other "necessary" items.

Since you have a '98, then disconnecting these wires wont cause a problem. On the other hand, doing so on a '97 and earlier models would disconnect one sensor which the vehicle uses for the speedometer and transmission. But again, you're fine since you have a '98.

As far as the "sounds like a torque converter issue...kinda" Kinda what? Like it is a t-convert isuue or... Can you elaborate please?

I was thinking more along the lines of a transmission "shudder" . My E-350 Econoline van has a "shudder" at 3rd and 4th gear but goes away once the vehicle goes over ~45 mph. The shudder is due to the torque converter in the transmission.

 

[White98]

Interresting what you say about the torq. The trans was my first suspect. I kinda thought first that I warped the flywheel upon re-install of the motor, bt quickly dismissed that idea b/c there is no shudder reving the engine in "N". What would cause the converter to shudder like that? Could low fluid cause that? It seems that the issue is from 1st to 2nd @ around 30-45mph...

 

[White98]

Alright. I think that I found my problem. I disconnected the "main" plug from the x-fer case and took her for a spin. The shudder/vibration went away completely. Sounds like my ford buddy was right about the t-case trying to engage during acceleration. Now the question is, what needs to be replaced and or adjusted inorder to remedy this situation. I assume that there is some sore of VSS to sens the speed of both the front and rear axles? Can someone point me in the right direction. Thanks.

 

[IZwack]

If it is indeed the VSS, then the rear one is located right under the output flange. It has I think three wires going into it. The VSS for the front I believe is to the side of the output flange.

Both of them are solid-state hall-effect sensors so there are no moving parts on the sensor itself.

 

[White98]

I will start there TVM.

 

[Opera House]

Cleaning the sensor may do it, they can pick up metal particals and start missing pulses. The clutch itself is three balls climbing a ramp, this is driven by an eddy current magnetic disk. I bought a rebuild kit without investigating too much and the kit comes without the clutch plates or chain, thr two things I wanted. I would really check fluid levels although my experience indicated problems with slow speed turns.