CJ7 lifted w/ excessive drive shaft angle

[CraigMAK]

I am rebuilding my CJ7 - never done anything like this before so am bumming my way forward (or backwards - not sure) Have the motor in and have got to the rear drive shaft which is a Tom Woods Double cardan. I have also installed a new Rubicon Express 4.5" lift so has new 2.5" springs - The perch is standard - axel under springs and I am having similar problems with the angle of the rear drive shaft being excessive (in my opinion). measured today at 28 degrees. Any advie or suggestions would be most welcome.

 

[CJ]

A double C should easily handle your lift even though you have a long 4l60e. The double C should compensate for any irregularities.
There are three angles that really matter.
1) Pinion angle to ground.
2) Pinion to drive shaft angle.
3) Transmission output angle to ground.
(Assuming ground angle to be zero)

From there all relative angles can be calculated.

 

[TSB8C]

In my CJ7 with SBC and 700R4 plus Novak adaptor and Dana 300 , my rear drive shaft is also quite short and I was concerned about a steep angle. I have a 4" spring lift. As CJ stated, the angles of the pinion to the drive shaft and the Transfer Case output to the drive shaft are critical. These two angles should be as close to a match as you can. You don't want one level (zero degrees) and one angled. Either both level or both angled equally. This is for a standard drive shaft. I used shims on the rear spring mounts to angle the pinion up slightly and spacers to drop the skid plate (and thus the Transfer Case output) down slightly. Mine are 4 degrees, meaning they angle the rear pinion up that amount. Then my Rough Country lift kit had the needed spacers for the skid plate to drop the Transfer Case output angle that same amount. Here's a pic of my skid plate spacers and the rear diff angled slightly upward. You can see that my rear drive shaft is not steep at all with this setup. 75 mph on the freeway and no vibration issues at all.



And here's a quick diagram to show what I'm talking about (I'm using the bottom option). And also here's a diagram showing a double-cardan (CV) shaft). Notice the difference in Transfer Case output angle (no drop, but pinion is still angled up).

 

[CJ]

As @TSB8C posted. A proper DC driveshaft setup will work for you. Rear pinion zero degrees to drive shaft.

 

[CraigMAK]

Thanks - since receive more info from Tom Woods asking for measurement as above. I will take these and repost once done. Won't be till next week. Family is distracting me from my Jeep for a long weekend away

 

[CJ]

Thanks - since receive more info from Tom Woods asking for measurement as above. I will take these and repost once done. Won't be till next week. Family is distracting me from my Jeep for a long weekend away

A little confused... I thought you already had a drive shaft? If not, you are proceeding well...

Have a great time with the family!