So I have recently installed a TF 4" kit and new Adam's driveshafts. I was measuring the pinion angle and driveshaft angle and came up with 4.5 degrees pinion and 7.5 degrees driveshaft. I will note that with the naked eye you really can't immediately tell the difference.

My question is whether this is far enough different that it needs to be adjusted ASAP? Or if adjusting it really depends more on vibrations and if there's no vibration why mess with it?

 

That's not a bad driveshaft angle for 4" lift. If it runs smooth I wouldn't worry about it. Mine ds came out to around 10* & 5* pinion angle and it is smooth. I have the zeppa joint.

 

The rear should be -2 lower than the DS

 

That said it makes me think I'm within 1 degree. Does -2 mean snout down?

 

What should the front be? I know caster should be 4-5.5

 

Lower then what the driveshaft is.

Front is going to be a fine line between good drivability/caster and vibrations/pinion angle.

The higher the lift, the less caster you will have to deal with to have a decent pinion angle.

I was running 3 pinion but dropped it to 2 which should have my caster near stock 4,
U-joint/DS angle 4 degrees. No vibrations.

Every jeep responds differently.

 

I've only got a few days to work this out before traveling to EJS..... And I have a weird, rhythmic pulsating hum. At this point I'm assuming it has to be driveshaft but since I did the gears and driveshafts all at once I'm really not sure where the issue is. I'm almost ready to pull the front driveshaft just to eliminate it as one of the issues. The goal tomorrow is to reduce the rear to -2* on the pinion from -3* to see where that gets me.

 

Pulling the shaft (that sound wrong) would be a good place to start.

Sent from my Galaxy Note 2

 

For a double cardan shaft the shaft should be in line with the pinion and most of the angle is taken up by the double cardan joint.

 

Good luck with that in the front ^

Edit: "minimal"
You want -2 in the rear for pinion rise in the rear.

Front, just enough caster so you don't have vibes.
Depending on lift hight pinion angle is going to be around +2 or +3 with 3* or 4* separation (pinion/DS)
The greater the angle less u-joint life and chance for vibrations. Especially running deeper gears/higher RPMS.

The front can get away with a little more angle because its not under load.
A good amount of JK's are unable to run deeper gearing--enough caster for drivability--and not have vibes.
Only options are.
- cut rotate C's
- aftermarket axle like PR with 10* separation caster/pinion.
- lockout hubs. Driveshaft doesn't spin in 2wd.