grinding on acceleration

[muddeprived]

got another issue that popped up. I had this grinding after installing my sye and other crap a while ago. I ignored it for a while until i had $$ to get some shims to fix the angle back there. I stuck 2.5 degree shims to get the pinion down 2 degrees. The grinding was gone after that. Now, four months later, the grinding is back. It grinds when accelerating, near the high rpms and the grinding stops as it shifts and then starts grinding again as the rpms rise. Going up hill and accelerating causes real loud grinding. There's no grinding when i'm coasting or slowing down. I can feel the grinding through the chair and right below me. People who sit in the back can feel it real well. Could the pinion angle be out of whack again? What you guys think? I don't see how the pinion angle can change after four months. The packs were already settled when i installed the shims.

2" Old Man emu full packs
Old man emu AAL (4.5" total)
2" RC adjustable shackles
2.5 degree shims with sye.

[Mudderoy]

Would a failing u-joint cause this grinding? Perhaps the shims changed the pressure points on the bearings but since the u-joint was damaged, or going bad anyway the grinding is back.

Nothing better than having vibrations "after" installing a SYE!!! :smiley-scared002:

[muddeprived]

Would a failing u-joint cause this grinding? Perhaps the shims changed the pressure points on the bearings but since the u-joint was damaged, or going bad anyway the grinding is back.

Nothing better than having vibrations "after" installing a SYE!!! :smiley-scared002:

Could be. I am using a factory front driveshaft. The u-joints were "ok" when i installed it. I actually cleaned em out and regreased all the needle bearings before installing it. I'll have to pop it off and install my front shaft back there and see if it still grinds.

[Mudderoy]

Could be. I am using a factory front driveshaft. The u-joints were "ok" when i installed it. I actually cleaned em out and regreased all the needle bearings before installing it. I'll have to pop it off and install my front shaft back there and see if it still grinds.

That's a perfect way to check. I sure do like that redundancy. I wish Tom Wood's SYE was like that.

[ol"blue]

Check the u-bolts. The axle's rotating slightly under load causing the yoke/u-joints to hit/bind but rocks back to normal under decel/cruise conditions.JMO

[Mudderoy]

Check the u-bolts. The axle's rotating slightly under load causing the yoke/u-joints to hit/bind but rocks back to normal under decel/cruise conditions.JMO

Yeah that's a good idea too. You might fix the situation when you swap drive shafts and not realize it.

[muddeprived]

Check the u-bolts. The axle's rotating slightly under load causing the yoke/u-joints to hit/bind but rocks back to normal under decel/cruise conditions.JMO

I was thinking about this. I am running old man emu springs and they are kinda soft. They are paired up with 2" shackles so i thought maybe this was softening them up even more causing some axle wrap.

[ol"blue]

You can't stop axle wrap without hurting flex though. Just thinking, but with the 2" shackles shouldn't you use a little bigger wedge to compensate for the shackles lowering of the rear of the spring, which tilts the axle pinion up slightly? Or am I over-thinking this? This is all new to me, as my Jeeps are both still stock. :confused:

[BlueXJ]

Were the shims and shackles installed at the same time? You may have to empty your wallet and get a SYE now that the grinding is back.

[muddeprived]

You can't stop axle wrap without hurting flex though. Just thinking, but with the 2" shackles shouldn't you use a little bigger wedge to compensate for the shackles lowering of the rear of the spring, which tilts the axle pinion up slightly? Or am I over-thinking this? This is all new to me, as my Jeeps are both still stock. :confused:

You are right but I did install shims after the full packs and shackles were already on so the angle should be correct.

[muddeprived]

Were the shims and shackles installed at the same time? You may have to empty your wallet and get a SYE now that the grinding is back.


Blue, I installed the full packs and AAL first followed by the sye and front driveshaft and four degree shims. Later I installed the shackles and it threw off my angles so i installed 2.5 degree shims. No vibrations since until this week when it came back, worse than it originally was.

[muddeprived]

Well I got down and dirty and checked into this problem. My rear pinion angle is 2 degrees down from the driveshaft. CHECK. All bearings associated with the driveshaft have zero play. CHECK. CV assembly is in good working order. CHECK. U-bolts nice and tight. CHECK. U-joint at the axle yoke has one dried up seized cap that will not turn. ISSUE FOUND. :cheerleader:


BUT....(theme to Jaws playing)...i ended up snapping a yoke bolt up on the dana 30. Son of a ..... I'm gonna have to drill and ez-out that darn little bolt. I already ordered a new strap and bolt kit from 4wd.

Jeeps....:boohoo: