Vibes after 1" lift, what to do??

[srimes]

I wanted to see how the pinion angle changed under load so I made this video:

http://video.google.com/videoplay?docid=-3910593104158447779&hl=en

It's hard to tell at low quality but it looks like it changed 2 to 3 degrees before the brakes wouldn't hold. This was in low range. Looks like the standard guidline of setting the pinion angle 2* down applies here.

 

[razor2006]

My Pro-Comp aluminum 2.5* shims should be here Thursday or Friday. I plan to install it before taking my road trip. Which way should I install it? Based on what I had posted my angles as earlier, should I put the shim in with the fat end toward the front or the rear of the vehicle? If I don't get the shims until Friday I'm going to be putting them in, in a bit of a hurry, so I don't really know if I'll have time to put them one way, then have to reverse them if it's not right. If they come Thursday, its no big deal. Just wondering if you guys have any idea. Thanks!

 

[Ramsey]

If they just slip on, make sure you still have enough of the head left to go in the center hole on the perch, and be sure to torque the bolts to spec and recheck after a couple hundred miles.

 

[razor2006]

Definitely will. Any idea on which way to actually put the shim in? Fat end toward engine, or fat end toward rear?

 

[slipslap]

So you have no lift in the rear and your thinking you need a SYE or transfer case drop or shims in the leaf springs? I'm missing something hear I think. I am running 2" lift with stock controls arms, stock track bar and stock sway bar up front, no sway bar in rear. And mine rolls great down the road with 31s.

I don't think these solutions presented will fix what your feeling. Have you had the tires properly load force balanced? Thats good place to start and if it doesn't correct it, get it on lift put it in gear and see if you can see or hear something.

 

[Blaine B.]

How are you checking the rear ujoints? If you leave it in park and such it'll appear tight. I knew I had a rear ujoint going out. However when I checked it with the Jeep in park, everything was tight.

You have to set the parking brake and leave the trans in neutral. Then I found out which joint had play!! It was giving me vibrations as well.

So that is why my transfer case is apart right now. Why replace the ujoint when I have an SYE to install and a new driveshaft? Heh. Better do that now!

 

[slipslap]

Definitely will. Any idea on which way to actually put the shim in? Fat end toward engine, or fat end toward rear?

If you want to raise the pinion, put the shims in from the backside with the fat end towards the rear. that will ush the rear of the spring perch down which will rotate the front side with the pinion up.

 

[razor2006]

If you want to raise the pinion, put the shims in from the backside with the fat end towards the rear. that will ush the rear of the spring perch down which will rotate the front side with the pinion up.

Is that what I need to do based upon my angle measuring earlier?

Okay, here's what the magnet base angle finder I have here at work tells me. With the magnet stuck on the flat spot with the hole on the side of the diff cover (I checked both sides they read the same), starting point would be 90* from this direction, I get 81*. With the magnet stuck on the top of the valve cover, starting point from this direction would be 0*, it reads 6*.

So in association if the needle were to start at 90* on both points I would get 81* beside the diff, and 94* on the valve cover, or if it were to start at 0* on both I would get 6* on the valve cover, and 11* beside the diff.

That would make me at a 5* difference. How do I figure this out from here? Does this mean I would need a 5* shim?

no,you cut it in 1/2 which gives you the 2,5 degrees you need. neat trick with the angle finder on the valve cover. If I ever new it I'd long since forgotten it.I'm an old fart but your'e never too old to learn. And shame on me for not mentioning retorquing the u bolts

So do I need to raise the pinion up or move it down? I really have no idea on this so can you tell me which way I need to go based upon my measurements?

 

[Ramsey]

Take a pic of the pinion angle, you give us a degree measurement, but not whether it is - or +.

 

[slipslap]

Typically if you lift a vehicle you would raise the pinion up some towards the transfercase out. But I am running about 4"-5" ( hard to tell when ya make your own spring packs ) in my CJ7 and don't use any shims and she rides fine. Well as fine as can be expected on a 26yr old rig.

 

[razor2006]

As far as the angle goes, the best I can give you right now is what the angle finder told me when I placed it on the flat spot by the diff cover. Starting point being 90* it read 81*, if the starting point were 0* it would translate to read 11*. I'm not really sure how else to measure this angle. I really don't know much about measuring angles and such.

 

[RCP Phx]

Dude,best evidence yet!Your way high in front for "a non-sye"(stock) set-up.Yes the fat end of the shim will face the front of the jeep.

 

[Ramsey]

It looks fine actually, yeah technically you are suppose to have them both at the same angle without an sye. I'd jack it up and check for play in the joints, or just replace them, only 15$ and some time.

 

[Ray H]

Those angles look nearly the same as mine, but Im sitting at 3" and I have a SYE. Looks to me like that pinion should come down a couple degrees.

 

[razor2006]

It looks fine actually, yeah technically you are suppose to have them both at the same angle without an sye. I'd jack it up and check for play in the joints, or just replace them, only 15$ and some time.

It's definitely not the u-joints. I just had them replaced with $25 a piece greasable u-joints last week.

Those angles look nearly the same as mine, but Im sitting at 3" and I have a SYE. Looks to me like that pinion should come down a couple degrees.

I'll stick the fat end of the shim toward the front of the vehicle then.

EDIT:
I just checked the UPS tracking on my shims, and it's showing they're out for delivery, so I should have them today. I'll try them fat end toward the front and see how she does. If that doesn't fix it I'll try reversing them. I have a few days to play with the shims before i go on my trip if they do indeed come today, so that makes me breathe a bit easier

 

[srimes]

If they just slip on, make sure you still have enough of the head left to go in the center hole on the perch, and be sure to torque the bolts to spec and recheck after a couple hundred miles.

What is spec? I just snugged them down with the air rachet...

 

[razor2006]

Not sure. Maybe check in a Haynes Repair Manual? I don't even have a torque wrench so I just crank them down as hard as I can with a 17" long 1/2" drive ratchet.

 

[Ramsey]

Around 80-100#, dont know offhand, at least try to torque them evenly.

 

[RCP Phx]

First,back to basics:http://www.4xshaft.com/driveline101.html
Second,Razor I just realized you have a 97+.You may never get rid of the vibes unless you do a SYE kit.I had minor vibes with my stock 2000 when I bought brand new.When I first lifted it I tried a Hack/n/tap kit,while it was better it still had some vibes.It wasnt untill I bought a HD SYE kit that it had no vibes,still good 8yrs later at 6" of lift!

 

[razor2006]

Okay, well I installed my 2.5* shims with the fat end toward the front of the vehicle, and it seemed to have helped with the vibes a little bit, but they're still there. I'll use the angle finder tomorrow at work and see what angle my pinion is at now. Any suggestions?

This next statement is blasphemy I know, but rather than messing with a TC Drop or SYE, I'm getting highly tempted to trade in my XJ on a Silverado. My uncle works at a Chevy dealership, and I'm getting tempted to try to see what kind of deal he can get me, and let the next owner of my XJ deal with the driveshaft issues down the road.