04 LJK Repair, Redo, Recycle - The 3 R's of a First Build

BuildBreakRepeat said:
I call BS on angle....how close does that new exhaust get.
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No where near.
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Cross-Threaded-06TJ said:
Throw your protractor on the tube real quick, what's the slope? That looks like its not even 15 degrees? Probably closer to 12. Which would put the CV Joints at 7-8 degree operating angle or less. No way its the shaft angle.

And your pinion angle looks perfect in that pic.
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Ya it's just slightly below on-line. Don't have a working angle finder right now.

The front driveshaft does need to come up some. I have a slight vib at 35mph.
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So interesting find the rattle goes away in 4wd and I get a "whine." Is this standard? Next step is disco front driveshaft and do same test. If the noise does away with front driveshaft I don't know if it is necessarily the DS or if it's the weight on the output shaft of the TC?

 
B00mb00m said:
So interesting find the rattle goes away in 4wd and I get a "whine." Is this standard? Next step is disco front driveshaft and do same test. If the noise does away with front driveshaft I don't know if it is necessarily the DS or if it's the weight on the output shaft of the TC?

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I'm curious if It goes away with it out. It may just be the harmonics.

It may mean nothing is "wrong" either. You could look into locking hubs?
 
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Not sure if it's good or bad news but the rattle does not go away with front shaft removed. In fact, with front shaft removed the rattle doesn't stop in 4high either.

This is pointing to a resonance / damping issue which is actually what it sounds like also (loose rattle).

So I'll reconnect the front driveshaft. Still kind of interested in why the guy from AA thinks my rear driveshaft is causing the rattle...

I'm going to see if I can make a bit more room around the case while I have skid and DS off also. I need a test to see if the noise is coming from inside the case or outside.
 
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Wildman said:
Since they think it's the rear then remove the rear shaft and drive it in FWD and see what happens.
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I haven't removed the rear shaft because I think I know the result. When the atlas is driving the fronts it doesn't rattle so I don't know what new data I would get from that test. I'm kind of done fucking with the rattle at this point I can not figure it out. I drove without the skid just to check and no change. Now I'm just going to dial in my driveshafts and run what I brung.

I went and picked up a magnet level with the gauge so I can see what's going on with angles on the driveshafts. I'm really terrible at eye-balling stuff. So the rear actually is a few degrees low. I'm going to adjust that up to 1 deg low.

On the front I have an axle with 11 degrees of pinion separation. With the pinion essentially aligned with the driveshaft I only have 3.4deg caster. To get back to my desired 6deg caster it puts me at about 3.5 deg below driveshaft center. Those are the two settings I'm going to drive next.
 
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Doesn't the JK axle have 10 D.O.S.? Not that 1 degree is a game changer. I always keep my pinion a degree or two below driveshaft angle for deflection under load.
 
sierradmax said:
Doesn't the JK axle have 10 D.O.S.? Not that 1 degree is a game changer. I always keep my pinion a degree or two below driveshaft angle for deflection under load.
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If you are setting for deflection under load, the front lowers under load so you would set it high, the rear rises under load, so you would set it low.
 
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sierradmax said:
High or low front pinion, does it matter?
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Another way to clear that one up is to consider whether or not the driveshaft changes the direction it turns to move the vehicle forward. Regardless of high or low pinion, the driveshaft direction did not change, it still turns the same direction for both high and low pinion.
 
mrblaine said:
Another way to clear that one up is to consider whether or not the driveshaft changes the direction it turns to move the vehicle forward. Regardless of high or low pinion, the driveshaft direction did not change, it still turns the same direction for both high and low pinion.
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Thanks for sharing. Makes sense
 
sierradmax said:
High or low front pinion, does it matter?
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Another thought- The pinion for the front is behind the axle, the rear axle would have the same reaction to rotation if the pinion was behind the axle. The driveshafts would also have to turn opposite directions which would make for a really interesting design for the transfer case.
 
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sierradmax said:
Doesn't the JK axle have 10 D.O.S.? Not that 1 degree is a game changer. I always keep my pinion a degree or two below driveshaft angle for deflection under load.
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This housing had clocked C's from ECGS. The stock jk has like 6dos which would be really bad for my application.
 
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