Phasing Transfer Case Drive Shafts?

[Fitz98]

98 Expedition 5.4 BW 4406 transfer case.
I read somewhere that the front and rear drive shafts have to be phased with each other?
Is there any truth to this and if so, how do I do it?
I did notice upon disassembly that there is a 2 piece drive shaft on the front and there is definately only 1 way to mate up those 2 shafts, but other than that, there were no spline limitations that would restrict where the transfer case goes into the transmission or into the rear dive shaft.

 

[LargeCarManX2]

When I take out my drive shaft/s I mark the pinion yoke and drive shaft to assemble the same way it came apart. If you have not done this, you may need to take off the yokes and have a drive shaft repair shop phase them for you. Make sure to get the grease type zerk u-joints and if you take off the yoke make sure your seal is still useable.

 

[default]

Im confused, how could one possible sync the two shafts, in an AWD system, they can spin at different speeds, in a 4x4 system one usually isn't turning.

 

[Fitz98]

Exactly...that was my thought too, causing the question. Perhaps it had something to do with the fact that the front shaft is a split shaft (2 parts), hence the limiting splines in those 2 shafts only allowing those two halves to assemble one way.

 

[asand1]

You only need to phase the two u-joints on a single shaft. Like so ]--------[

 

[LargeCarManX2]

Originally Posted By: asand1
You only need to phase the two u-joints on a single shaft. Like so ]--------[


Also, with the ------] transfer case [------ as marked, you would want the yokes like this as well.

 

[asand1]

Originally Posted By: LargeCarManX2
Originally Posted By: asand1
You only need to phase the two u-joints on a single shaft. Like so ]--------[


Also, with the ------] transfer case [------ as marked, you would want the yokes like this as well.


The transfer case yokes tun independently of each other in 2wd, so no, after driving 6 inches in 2wd they will be out of phase anyway.

This driveline is in phase

This two piece driveshaft is also in phase

 

[asand1]

When turning a circle, the front tires turn a wider arc then the rears. This will cause your front drive line in an AWD system to turn more revolutions than the rear. Thus, your front drive shaft will be out of phase with the rear.

In a part time 4WD system, the front diveshaft is motionless, as the rear spins away while in 2wd.

Your transmission output and transfer case input need no phasing, as they are not universal joints. Phasing is required in ujoints due to the rotational speed of the shaft oscillating as the u-joint trunnion changes angles.

the driving joint loses some speed, and the driven u-joint adds some back in.

 

[asand1]

The resulting "vibration" is actually the harmonics created by the oscillations in drive shaft speed being transmitted to the ground as pulses of torque/RPM.

 

[Fitz98]

Thanks to everyone for clearing that up.
Ford did a good job of making it foolproof, since it is something I would have overlooked. On my truck, the front drive shaft yoke had 2 splines with a weld between them, making it in essence a double spline and the receiving shaft had 1 spline missing to line up with the matching yoke.
The rear shaft and transmission shaft had no limiting factors built in.
asand1 did a great job explaining why. Thank you, now I can have piece of mind that there is no other phasing to consider when puting it back together.

 

[LargeCarManX2]

Originally Posted By: asand1
Originally Posted By: LargeCarManX2
Originally Posted By: asand1
You only need to phase the two u-joints on a single shaft. Like so ]--------[


Also, with the ------] transfer case [------ as marked, you would want the yokes like this as well.


The transfer case yokes tun independently of each other in 2wd, so no, after driving 6 inches in 2wd they will be out of phase anyway.

This driveline is in phase

This two piece driveshaft is also in phase

Correct phasing photo's for drive shafts...however, depending if he has generation 1 or two transfer case in his vechile.....my limited understanding is the transfer case does the two to 4 wheel connection. The drive shafts turn all the time and the transfer case connects which set (front or back) to power internally. So, the phasing of yokes is important on each output shaft of the transfer case in my opinion. One way to tell if it is generation 1 or 2 is the transfer case shifter knob. I may be wrong and if anyone really knows....please let us know. My Ford has the locking hubs and old style LOW, High, and the front drive shaft does not turn until the transfer case is in 4 wheel position.

 

[OVERKILL]

Originally Posted By: LargeCarManX2
One way to tell if it is generation 1 or 2 is the transfer case shifter knob. I may be wrong and if anyone really knows....please let us know. My Ford has the locking hubs and old style LOW, High, and the front drive shaft does not turn until the transfer case is in 4 wheel position.


Nope, I'm pretty sure you are correct there. Our '98 had 2HI, AUTO, 4HI, 4LO, whilst our 2000 and 2002 have AUTO, 4HI, 4LO.