Rear ZJ vibes after lift

[Reznor]

98 5.9 was fine before the lift.

Lowdown: f>r swap lift.   Rough Country 3.5" with fixed lower control arms.

Lots of rear vibration on accell especially between 30k and 80k.  Smooths out at 100k.

Rear pinion angle and tc output roughly identical; no more than 2 degree difference.

Adjustable control arms wouldn't help with it being damn near dead on right?

Tried a 1" tc drop and it might actually have made it worse.

Ujoints appear to have little play - though I haven't taken the rear DS off so it's hard to tell.

Front driveshaft removed to replace cv with ujoint slip ds.  So far still removed to isolate rear issues first.

Any help would be appreciated.

[cjust]

Sorry to go off topic i got some rear lift coils if you want.... Cheap

[cjust]

My zj just had my 5.5" lift installed with fixed rears and it has  0 vibes. So your pinion angle must be off

[Reznor]

I know zj's are supposed to lift wonderfully without the sye and all that jazz.  But I swear, the pinion angles are 2 degrees off at most - and I thought that was an acceptable difference?  If I need adjustable uppers I'll buy them - but I don't want to burn cash.

cjust - I think I saw you selling coils.  Thought about it, then realize my fronts actually work just fine for me.  Thx.

[cjust]

Are your uppers fixed now?

[apeman]

Have you taken a look at your trans mount and engine mounts ?

[Reznor]

Uppers are currently stock.

No, have not looked at mounts - but why would they fail the very moment I put the lift in?  It was fine.

[apeman]

I had a wierd vibe after doing my lift. Turned out my trans mount was shot. Cleared itself up after changing it out

[Reznor]

ok thanks - I'll check it out.

[JackstandJohnny]

98 5.9 was fine before the lift.

Lowdown: f>r swap lift.   Rough Country 3.5" with fixed lower control arms.

thats your problem right there. rear arms are to long with this kit.  common problem with the RC F/R (according to the interwebs) adjustable uppers should fix it or swap the stock ones back on

[Reznor]

Yeah, that's what I'm thinking.  Even though the angles don't look too out of line, if it's primarily happening on acceleration then it's probably pushing the pinion down a couple of degrees more than it likes. 

Looks like it's new uppers. 

I have to install the front driveshaft to see if that requires new uppers as well.  However, if I'm right, acceleration (with front wheels engaged) would have the opposite effect and bring the pinion up - so I might be ok as long as the fixed control arms don't push the pinion too low under non-acceleration situations. 

I WAS getting horrible vibes from the front as well, but I know that very likely would have been caused by the axle-side CV that used to be there.  It was on quite an angle after the lift. 

Fingers crossed.

[cjust]

Listen to johnny. Hes a zj guru.

[morerpmfred]

Set of uppers for sale here. Not mine. http://forum.calgaryjeep.com/index.php?topic=28990.msg181355#msg181355

[apeman]

Seriously??? Johnny is a burger joint guru. He's never had a zj that didn't either get parted out or backyard butchered.

[cjust]

[hquote author=apeman link=topic=29033.msg181572#msg181572 date=1400890631]
Seriously??? Johnny is a burger joint guru. He's never had a zj that didn't either get parted out or backyard butchered.
[/quote]aw man thats just cruel