Pinion angle problem???... HELP NEEDED

Helping a buddy upgrade his 78 cj5. He picked up a nice set of axles from a 74 cj5 (flanged 44 rear). The gears were also better from the 74, so the decision was made to use both the front and the rear from the 74.

With both front axles on the bench, the pinion angles are different?? This is very puzzling to me, as both are cj5, both have/had the dana 20 t-case and both use a dana 30 front axle. The 78 D30 pinion angle is approx. 10 degrees... while the 74 D30 pinion angle is only around 2 degrees? The caster appears to be the same on both.

I have checked these 2 D30 axles no less than 10 times with a degree indicator and "it is what it is". Has anyone else run into this? I sure hate for him to have to remove and reposition the outer knuckles and perches... is there a short cut here?? Maybe a double cardan on the front driveshaft would solve the problem? (easier than relocating the knuckles, perches, etc.)

Any advice would be GREATLY appreciated, we are stuck.

Thanks

 

Maybe by the time 1978 rolled around, they figgered a little more pinion angle wouldn't be a bad thing. I say run it. If there is some negative consequences, swap the gears into the newer housing. No big deal

 

Suspension is different between the two hence the angles are different (springs are different length/width). Also the frames and spring mounts are different so that also accounts for some differences.

 

I would advise him to switch the gears over, but the housing is shot on the 78 front end (broke at the tube-center section junction)

 

www.car-part.com

 

How does the caster compare between the two axles with the spring perch @ 0 degrees? Is it also ~ 8 degrees off between the two?

 

The caster is the same on both axles. My buddy called a regional, well respected jeep parts & restoration company (to remain un-named lol) today and they believed someone may have changed the pinion angle on the 78 front axle, based on the 10 degrees. BUT that doesn't explain the caster being the same?? Basically recommended he install the 74 axle and go. They apparently had no info on variations of pinion angle between the intermediate and the late model (4 years apart).

This appears to be the best explanation. I picked up a Waggy D44 front for my project. It has a 10 degree pinion angle, because it used a CV type joint at the T-case.

Did ANY jeep vehicles come with a narrow width, D30 front axle that used a CV type (double Cardan, etc)?? I am not aware of any. The mystery continues, we'll see what happens when he installs the 74 axle.

BTW the rear pinion angle was different as well. He set the D44 from the 74 up just as the 78 was set up.

 

A double Cardan joint IS NOT A CV JOINT!
There is a velocity change with a double Cardan joint, it's just split between the two Cardan joints so the velocity change is halved. But there is still a velocity change with angularity. Steeper the angle the more the velocity change. A Constant Velocity (CV) joint does not have a velocity change as the operating angle changes.

 

Thanks Nick.. I'm well aware of the differences. I'll try to me more literal in the future.