Post lift vibration

[Ryanoceros]

I know, I know. The 400th vibration post of the month, but I promise I've done my due diligence haha.

Now that I've gotten my PCM issue figured out, and can drive, I'm getting miles on my gears and sorting out vibes.

I've got:
4 inch springs, front and rear upper and lower adj control arms, sye and dc rear shaft, oem DC front shaft (adams front on the way), the stock front shaft has been rebuilt a year or two ago and balanced a few weeks ago.

If I remove my front shaft the LJ drives great, so I've gotten that far. I rechecked my angles and it had changed a little after everything settling. I was at 9° pinion, 8° shaft. I readjusted to 7° pinion, which also lands me at ~5° caster. That puts me in a great spot for both angles with no compromise. Toe was set by a shop. The vibes got about 50 or 75% better but it's still sinusoidal at 50+ mph. Too fast to be tire vibe. I doubt the new front shaft will change anything but I wanted/needed to get one anyways. My figuring is that it MIGHT be the centering ball on the shaft or tcase front output bearing. The bearing spins good, sounds kind of loud, which idk if that's normal or not, and has probably 1/16th inch up and down play in it. Not enough to really see but I can feel and hear it. It looked good when I did the SYE.

What do you fellers reckon? I'll update after I change the front shaft out but I wanted to get opinions on that bearing.

I appreciate you dudes.

 

[speeding_infraction]

I'm no expert, but I would think bearing play should be in thousandths of an inch not fractions. Add in that the bearing would expand with heat and that might be your problem. Maybe there's a website somewhere or the FSM that goes into detail on assembly tolerance?

 

[Ryanoceros]

I'm no expert, but I would think bearing play should be in thousandths of an inch not fractions. Add in that the bearing would expand with heat and that might be your problem. Maybe there's a website somewhere or the FSM that goes into detail on assembly tolerance?

I can probably put a dial indicator on it and measure it at the end of the yoke to tell you exactly. I had a driveline shop balance the shaft with the yoke and they made no mention of it either, just something I noticed when I was fiddling around.

 

[macleanflood]

Try moving the front tires to the rear or get them balanced.

I'd dial the caster down a turn at a time on the front control arms and see what you see.

-Mac

 

[rasband]

It sounds like shaft itself or pinion angle, but @macleanflood 's approach helps dial in while you wait.