I think I have an issue with my rear two piece drive shaft.
The D*mn center bearing (part that joints the intermediate drive shaft and rear drive shaft) keeps coming apart. I have replaced this thing about 3 times and it goes bad by 25K miles. How can you tell if the shaft is out of balance and if so how to fix it ?
I have heard of going to a 1 piece drive shaft, anyone with experience there ?
Center Bearings are expensive <img src="/forums/images/graemlins/barf.gif" alt="" />

A local drive line shop can check the balance for you.

Also check the alignment:
- http://www.4crawler.com/4x4/ForSale/Shims.shtml#FAQ1

2->1 conversion:
- http://www.4x4wire.com/toyota/tech/driveshaft/

Thanks Roger,
The alignment I am refering to is not the angle but the sequencing of the shaft itself. The alignment of the flanges and yokes is what I am refering to. I checked it last night and the zerk fitting and flanges are not in the same orientation (facing the same way). My rear pinion flange is out of alignment with the center support bearing flange by 45 degrees. That tells me the flange on the center support bearing may not installed correctly. If my memory serves me well all zerk fittings should be in the same orientation (all facing the same way) and all yokes are orientated the same way. According to my toyota factory service manual there is suppose to be an alignment mark on the center support bearing flange which is to be aligned to a mark on the intermediate spline shaft. I suspect the spline slip yoke on the rear drive shaft came out of the rear drive and was re-installed out of rotational alignment and or the center support bearing flange is out of alignment. Does anyone know what the alignment of these items should be ?

What is the actual type of joint at the center bearing? Is it a u-joint or a CV? If a CV, then the phasing (flange alignment) is not so critical, but with a u-joint, proper alignment it of the utmost importance:
- http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Phasing

It is U-joint, there are no CV or cardon joints in this rear two piece drive shaft.
The drive shaft on the left is like mine:

See how the yokes, flanges and zerks line up <img src="/forums/images/graemlins/baby.gif" alt="" />

Look at this pic. Notice that the u-joints are perfectly aligned with the red line? This is proper phasing. Make sure yours is phased correctly.
If so, pull it apart and flip it 180 degrees, so it's phased properly again. This sometimes helps.

Yes, the top half is phased right, but the bottom half is not, that is what must be in phase to run smooth. The top half runs at a very low angle, but the bottom half is at a much steeper angle.

I take it when you say "top half" and "bottom half" you are relating to the picture and to the two piece drive shaft?
bottom half (short shaft)- mates to the tranny.
top half (long shaft)- mates to the rear end.
I must be missing something here, if I read both of of your posts (Staceman, 4Crawler) it sounds like the statements on which end of the the shaft needs rotating conflict with each other.
Is the part of the shaft with red line correct or the part at the top of the picture ?

It looks like to me you mean the top half in the picture which mates the rear end is out of phase and you would need to seperate the long shaft at the splined slip yoke rotate it 90 degress (1/4 revolution) and hope you are not out by 180 degrees, correct ?

If you rotated it 180 degrees you would end up woth the same orientation.

I found this write up on jeep applications on the subject of drive shaft phasing:
http://jeepgarage.free.fr/OWN/drive%20shaft%20alignment.pdf

It should still apply to my drive shaft combination, note "Dual Shaft with Slip Shaft" references in the diagrams.

Comparing the two piece drive in the picture to the Dual shaft with Slip shaft diagram in the pdf it looks like they have the same yoke orientations (phasing), am I wrong here ?

I was referring to the "as installed" configuration, top half being that connected between the t-case and the CSB, bottom half between the CSB and the differential.

Any 2 u-joints on a section of shaft MUST line up with each other:
- http://www.4crawler.com/4x4/CheapTricks/Images/2joint_angle.gif



And here is an animation showing why:
http://www.4crawler.com/4x4/CheapTricks/Movies/ujoint.avi

Notice how the shaft speeds up and slows down over every 1/2 revolution.

I think I got it, were the confusion comes in is in the picture of the drive shafts. I think the joint at the top of the picture (mates rear end) is identical to the joint at the bottom of the picture (mates transfer case). You just can't see the ears on the drive shaft. That joint at the top of picture moves in all 4 directions (up, down, left right) in line with all other joints. <img src="/forums/images/graemlins/scared.gif" alt="" />