Vibrations (not good) klnd of long

Posted in modified as well but, you guys have always been helpful.

History of my situation:

I bought my '96 about 7 years ago...totally stock (4.0 HO, AW-4, Chrysler 8 1/4").....from day 1 I always had a slight driveline vibration.

Intalled a Pro Comp (I know) 3 1/2" lift, 31" BFG ATs, 1" wheel spacers and ran it that way for a year or so......no real change in vibrations.

Found and installed a D44 that I adapted Ford Explorer discs to....still had vibrations.

Put together a (around 4 1/2"-5") lift from various parts I had been stock piling over the years ie: custom made adjustable lower arms with flex joints, drop brackets, 4 1/2" RC leaves and shackles, yoke style hack and tap SYE and front CV shaft in back, 33x10.50 BFG ATs...still stock gears.....slight increase in vibes (not too bad though) because I needed to point the pinion up more.

Regeared to 4.88, No Slip in back, ARB in front (picked that up for $250 ), took me a couple of years to gather up all these parts.....vibes about the same but, shifted because of increased shaft speed.

Had my tires rebalanced, changed oil.....in preparation for a trip to Cedar City, UT (I'm moving there). Leave the house at around 11PM (I have an appointment with a title company at 9am). A couple of hours out, vibrations intensify to the point of getting violent (holy crap!) but, I'm forced to keep going because I have to keep my 9am appointment.
After I signed all the paperwork, I get under my Jeep and discover that the bolt holding the yoke on, is loose (as is the yoke!) tighten (and Loctite) the bolt but, I still have bad vibes but, not as severe as before.

Been trying for the last week to figure this out. Shimmed the pinion up to ideal angle and had it on my buddies lift, ran it up to speed....sounds like it's coming from the rear end but, could be telegraphing, opened up the rear end to reverify pattern and backlash and all seems fine (my buddy is a certified mechanic and very experienced in gear set ups). I also replaced all the u-joints and repacked the CV joint centering ball. I'm (we're) stumped.

I bought a Rugged Ridge shaft style SYE (smoking deal) and will install that tomorrow, thinking that maybe my trip to Utah with a floppy shaft might have damaged the t/c output shaft bearing so, might as well upgrade.

So, if this dosen't cure it, anybody have any ideas?.....could a bad wheel (axle) bearing act this way. I'm about to put a bullet in it (or me)!

Just to clearify, vibrations are speed/load sensitive....ease up on the gas and they lessen or go away.

HELP!

Hans

Here's a thought..... are your rear leafs so flexy that with change in torque they allow the axle twist the pinion up? I've seen that happen.... This will screw up your driveshaft angles as you drive.

Kejtar said:

Here's a thought..... are your rear leafs so flexy that with change in torque they allow the axle twist the pinion up? I've seen that happen.... This will screw up your driveshaft angles as you drive.

Click to expand...

Not hardly...they're Rough Countrys.

However, I just added shackle relocation brackets and shimmed the axle so the pinion sits at about 2* (ideal for a CV shaft).......it's driving me nuts!

Thanks,

Hans

Since the vibration has always been there have you ever taken the drive shaft off and had it balanced?

Renegade XJ said:

Since the vibration has always been there have you ever taken the drive shaft off and had it balanced?

Click to expand...

I was thinking the same thing.

Maybe someone could loan you a drive shaft with no vibes?

Renegade XJ said:

Since the vibration has always been there have you ever taken the drive shaft off and had it balanced?

Click to expand...

Vibrations have always been present (before and after SYE) and have since gotten really bad (I've had 2 different CV shafts on there) all of a sudden.
I'm really thinking I have a bad output shaft bearing.......having the yoke loose and spinning at 3,000 + rpm for over 400 miles probably wasn't good for it.

Think about how much mass is on the end of that puny output shaft (yoke, double cardan joint) and how far away it is from the bearing that supports it...I CAN feel a small amount of axial (up and down) play in the shaft.

I'll find out if my suspicions are correct when I install a "proper" SYE tomorrow.....wish me luck!

Hans

Hans, since you have a SYE. Remove front DS and drive.... then reinstall and remove rear DS and drive (in FWD)..... Should help identify source.

Id pull the drive shaft put the rear up on jack stands pull the wheels off and feel the pinion bearing... is there play in it? Does it spin freely? Is the pinon bearing bad? id go one step further and pull the diff cover to make sure your gears aren't chewed up. If this all checks out ok then id would pull each shaft individually as he suggests above to see if the vibes are in the front or rear.

I had the same set up except an 8.8. I had 2* as well on my rear pinion angle 4.5 lift after chasing it like you I found i still needed to drop my t-case cross member like most lifts do as I think the angle on the CV was to great. After dropping the case 1" I have 0* pinon angle up and down and no vibes. The only difference is the 8.8 pinion is offset from center giving me an angle at my pinion to the side. I don't know for sure if it was the compound angle at my pinion or to much angle on my CV....

Good luck

silverslk said:

Hans, since you have a SYE. Remove front DS and drive.... then reinstall and remove rear DS and drive (in FWD)..... Should help identify source.

Click to expand...

Hi Andy,
We had it up on a hoist and ran it so, the front shaft was never turning....definitely coming from the rear somewhere.

Rich69 said:

..........Is the pinon bearing bad? id go one step further and pull the diff cover to make sure your gears aren't chewed up. If this all checks out ok then id would pull each shaft individually as he suggests above to see if the vibes are in the front or rear.

I had the same set up except an 8.8. I had 2* as well on my rear pinion angle 4.5 lift after chasing it like you I found i still needed to drop my t-case cross member like most lifts do as I think the angle on the CV was to great. After dropping the case 1" I have 0* pinon angle up and down and no vibes. The only difference is the 8.8 pinion is offset from center giving me an angle at my pinion to the side. I don't know for sure if it was the compound angle at my pinion or to much angle on my CV....

Good luck

Click to expand...

If you read my (rather lengthy) post completely, you'll see that I did all that.....gears and bearings only a couple of months and a few thousand miles, old.
As far as there being too much working angle on the CV, I don't think so....my early Bronco has a lot more angle and dosen't suffer from vibrations besides, the vibrations went from barely noticable to "holy shit!" after the loose yoke, long trip incident.

I'd bet that if you raised your cross member back up, with 0* at your pinion, you'd no longer be dealing with a compound angle and your vibrations shouldn't return.

Hans

I'm thinking is has to be your tcase, because I think you've eliminated everything else. Swap in a different tcase?

Could it possibly be a shot tranny mount?

It could be your front driveshaft vibrating if you don't have locking hubs. Put the Jeep up on jack stands, put it in nuetral, then grab the drive shafts and check for any up and down play. Also take the front shaft off and drive around like that.

Oatmeal said:

besides, the vibrations went from barely noticable to "holy shit!" after the loose yoke, long trip incident.

Click to expand...

Not all jeeps were created equal in regards to vibes and to top it all off, you might be experiencing multiple issues on top of each other. Because you had the loose yoke and a long trip, try this: take off your rear driveshaft, make sure that your jeep is in 2wd, pop it in gear and give it a little gas (not much) and look underneath and see if the yoke is turning true or if it seems to be making some sort of a pattern with it's movement.....

my vote is going to be for one of the driveshafts.

start by pulling the fron shaft and driving around in RWD. if the vibe goes away, have the shaft balanced.
if it doesn't it

pull the rear shaft, put the front shaft on the front and drive in 4hi. if the vibration persists then your issue is in the T-case.

It's cured....the vibration demons have been exorcised!

Took the t/c apart to install the SYE and noticed a lot of very fine aluminum "dust" in the case and fluid....hmm.

Couldn't see any evidence of the chain or anything else making contact with the case but, the output shaft bearing was very loose in it's bore, allowing it to walk back and forth and rock up and down as well.

I believe the "dust" in the case and fluid was from the bearing wallowing out the bore in the rear casting.....in any event, it's dead smooth now and a lot stronger as well.

Thanks for letting me whine on here...heavy sigh of relief.

Hans

I'm glad to hear that you fixed your vibration problem!! I suffered from a very bad vibration problem myself and can understand the frustration. I was running a hack-n-tap flange sye on my np242 t-case. I had it on for years with no problems. I had two CV shafts go out on me, and at the time I was making a 45 mile one way trip to work 5 days a week which made the bearing on my main shaft go out and give the same vibration you were having. I was luck enough to come across a np231 that swapped right in. Although since I already have a flange style cv shaft i went with anoter flange stlye hack-n-tap. It served me well for years, and when this one goes out,I now will know what the problem is and how to fix/upgrade when needed.

Please keep tech threads in the Tech Forums

Please do not start duplicate threads.