Driveshaft angles and lengths

CK. the yokes on each to see if you may need 1 replaced more than the other?

 

I'd have it taken out of the rear shaft. That way you don't have to find a new mounting location for your carrier bearing. You may need to add shims to get your angles right though.

 

I have seen some unbelievable propshaft angles on old Mercedes trucks from the 60's & 70's.
They are still running fine.
Apparently it is more important to keep the input and output shafts parallel than in line.

 

I was taught to have at least a 2deg. Angle in the driveline. That will let the u-joints work . If you are installing the cross member for the carrier bearing, split the difference. If your going to be short enough of a wheelbase see if you only need one driveshaft. As long as you don't go over 6 ft in length.

 

I would not set it all the way in. With rear and frame twist you may run into issues. Your angles will be different. The yoke height will be different from the front compared to the back rear. You may have to change the angle of rear as well to get the correct driveline angles. This can be done by changing the wedge spacers under the spring saddles.

 

http://www.scientificbrake.com/service/

^These guys shortened and rebalanced a driveshaft for us a few months ago after we installed a new transmission in one of our trucks. They have a huge machine shop and will make driveshafts from scratch. If you can wait til Monday and call them, they will walk you thru the process and answer your questions. They are good people, I believe jason is the guys name in the service dept.
If the truck is at our yard tomorrow I will see which end was cut and snap a few pics for you

 

Honestly, it doesn't really matter as long as the angles are set up correctly. IMO, since you have no crossmembers yet, it's slightly better to shorten the front shaft and move the carrier bearing forward. The front shaft doesn't swing with suspension movement. Shortening the rear shaft will cause it to have a bit more angle and change angle more with suspension travel. If it's a typical air suspension, the U-joint angle on the axle changes with suspension travel and this could be harder on U-joints. Only moving the rear 6-8" is a small change in angle and probably insignificant.