hypedonmonster

So I replaced both rear driveshaft u-joints and that stopped all of the crazy vibes when I was decelerating. But I took my jeep on I-25 on Friday to go to the airport and right at about 75 mph the jeep just kinda has a pulsing vibration and a droning sound. Like it will vibrate quietly, then loudly, then quietly, then loudly I'd say about once every second and it doesn't stop. I've tried to outrun it but it doesn't stop but it also doesn't get any louder. I have some bad camber issues due to some bad upper ball joints and its worn my tires bald on the outside and pretty much new on the inside. Do you think it might be my tires off balance or my upper ball joints going nuts or what. Not too big of an issue as I rarely drive on the freeway but I have 3 trips to the airport and a road trip to Oregon all in the next 2 months and kinda wanna figure this out. Thanks for the help guys!

Gee oh Dee

Front ujoints? Trans/motor mounts?

Could be plenty of things. Start fixing what you know is wrong...

DieselD

Kind of sounds like you alignment (toe) is off.

hypedonmonster

It could be my toe I bet my toe is a little out of wack from my ball joints. Ill take a look at that and it can't be my front drive shaft because I never have it in 4x4 unless I'm off roading and it doesn't spin in 2wd. It might be a trans mount but I would think a tranny mount would make more of a clunking when shifting from reverse to drive, etc, not a droning or constant vibe. But I could be wrong. Honestly I'm leaning more towards alignment or out of balance tires. Ill start by replacing my ball joint this weekend though once I'm back in Colorado. ( in North Dakota till tomorow)

DieselD

It could be sooo many things, lol. Toe and tire balance is a nice (cheaper) place to start. You can rotate tires and see if anything changes too.

The front drive shaft does indeed spin in 2wd. Just no power to it. You could remove it and see if there are any changes.

hypedonmonster

I have never once seen a front shaft spin in 2wd, there's no power going to it from the transfer case and the jeep's "hubs" if you want to call them that are not locked so the drive shaft stays still and the spider gears in the axle move all of the momentum from the driver side tire to the passenger side half shaft, the vacuum hub connects the half shaft to the rest of the passenger side shaft making both axles connect to the carrier assembly but that hub only actuated in 4x4.

Anyways lets agree to disagree. I have new u joint on my front shaft too my buddy andi replaced them 2 days after I got it...well I replaced them and he "stupervised" haha.
So it's not the driveshafts. It's not tie rod ends or track bar bushing ( all of those are brand new) so it's either tire balancing, alignment, ball joints, possible trans mount, or all of the above haha

RobG

It does spin. I just had to take my front ds out because the double cardan joint is bad and it was knocking around under there...in 2wd.

hypedonmonster

It does not spin man. The carrier doesn't move at all so the drive shaft doesn't spin.the spider gears are all that move. You may have it move a little bit from friction between the spider gears moving the carrier but in 2wd the transfer case nor the axles move the driveshaft. Here's a test. Have a buddy put it in 2wd and drive it very slowly with you holding the font drive shaft. Trust me it won't move, and if it does you either need to service your front dif very badly or you have full time 4wd or your t-case is stuck in 4wd or your vacuum hub is stuck in the locked position. I'm willing to bet your hub is locked. But in a properly functioning 4wd system your front drive shaft should not move or move VERY little but have no power behind it.

DieselD

I don't know about the vaccum disco d30, but on non-disco d30s the only place the drive shaft is disconnected from the rest of the drive train is at the tcase. So yea if you put it up on a lift in 2wd then the shaft won't spin. In 2wd driving on the ground the shaft will spin... from the tires turning on the ground.

RobG

The 231 does spin. How else would you be able to shift into part time while moving?

Gee oh Dee

Awesome thread.

hypedonmonster

As far as I knew all Cherokees had Dana 30's with a vacuum actuated half shaft collar system that locked the half shaft coming from the passenger side of the dif to the rest of the passenger side axle. Thus acting as a "locking hub" connecting both axles shafts to the carrier. Is the vacuum hub is disconnected (as it should be in 2wd) ( if in proper working order) the driver side axle is connected to the dif, if the driver side axle turns, it will cause the spider gears to move, causing the half shaft on the passenger side to turn the opposite way. Once that vacuum collar is actuated, both axles will move the same direction cause info the whole dif to move thus turning the drive shaft. If the color is not actuated then only the spider gears should move, not the whole dif and drive shaft. And no matter what in 2wd the front drive shaft should not be being moved by the power of the t-case unless you have a full time 4wd like a v8 zj

RobG

Are we talking about it on a lift or driving down the road? I believe the wheels moving down the road is what turns it and its separated at the tc.

hypedonmonster

On a lift or down it doesn't matter. On these D30s on the passenger side there is no solid one piece shaft connecting the wheel to the dif. It is 2 smaller shafts that are connected when the hub is locked via vacuum. When that hub is unlocked the driver side axle shaft turns the spider gears and that turns the half shaft connected to the dif on the passenger side the opposite way. On the road or on a lift the spider gears are the only part that should move not the whole dif and drive shaft.

Gee oh Dee

Only early XJs had vacuum disco. Everything after 91 was without disco.