Engine/Transmission (1998.5 - 2002) Driveshafts in phase? (u-joints)

[GOT-Torque]

After having both driveshafts out and now putting them back in, do I just put the t-case in four wheel drive and ensure the u-joints in both shafts are aligned vertically?



How do they stay in phase? Because when you drive in two wheel drive the front shaft doesn't spin (its free to spin by hand though). Once you put it back in four wheel drive will they be in phase again?



I guess I'm confused on how the t-case keeps everything in phase?

 

[B.G. Smith]

I don't think you have to worry about front and rear being in phase on on 4 wheel drive. If you have a two piece rear drive shaft then it is necessary. bg

 

[Loren]

In phase doesn't refer to keeping the front driveshaft in phase with the rear, it refers to keeping the front u-joint on a driveshaft in phase with the rear u-joint on the same driveshaft. This can be a problem with any driveshaft with a slip coupling that can be taken apart. (Every driveshaft I've seen works that way, but I'm not a driveshaft expert. )



As a driveshaft turns and the u-joints bend, the shaft portion (between the u-joints) will not turn at a constant rpm. It will accelerate and decelerate through the action of the u-joint. If the two u-joints are in phase, this change in driveshaft speed is cancelled out at the other u-joint. In order for this to occur, the input and output shafts must be parallel to each other.



If you haven't changed the angles of either the output or input shafts (the transfer case and the differential), then they are close enough. Also, if you haven't taken your driveshaft apart at the slip joint, the joints should be in phase.



To ensure that your driveshafts are in phase, all you do is ensure that the yoke (the part that holds the cross) on the shaft is the same direction at each end of the driveshaft.



This is easier to show with a picture, but I don't have one. Check your driveshaft by ensuring that if one yoke is horizontal, the yoke at the other end of the driveshaft is also horizontal.



It's much simpler to do than to explain without pictures. I hope it's clear.



Good luck,

Loren

 

[GOT-Torque]

Thanks for the info. You did a good job of describing it. I was just unsure about needing to have the front and rear in phase with each other. I have seen the light and realize now that it doesn't matter between the front and rear.

 

[MLisle]

Driveshafts and U-Joints - Tom Sotomayor gives a good explanation (with pictures) of ujoint phasing.

 

[Loren]

MLisle,



Thanks for the link. That's the best explanation I've seen.



Loren