87Heep4wdv

Have some questions for you guys that know more on jeeps than I do. I have an 87 jeep Cherokee, I barely got it and I have a noise but don't know where it is coming from. At take off its non existent, at speeds from takeoff - 35mph it's not there. At 40-45 the noise is present.

Now I took the rear drive line off with the jeep on stands while accelerating, hoping it would help pinpoint the noise and there is no noise whatsoever. I did notice rear u joint was trashed, so I replaced it and put a new one on, thinking I wouldn't hear the noise anymore.
Now reinstalled, but noise is back and same around 40 mph. I've been told its the transfer case but it happens in 2wd, and I'm thinking noise is just traveling up the driveline to where it makes it sound like its under the ebrake handle. Well Im hoping at least.. Anyone care to chime in? People keep telling me transfer case and transfer case this and that but I am hoping not.

Might sound dumb but I drove it through grass with rear drive line removed and no noise whatsoever. So is it possibly the ujoint connecting to the yoke? The noise is similar to when you have something stuck to your tire and its flapping. Non existent at take off up to 35-40, then I start hearing it. Its a thud, thud, thud, thud noise. And gets faster as I accelerate. Sort of like I know its a rotating sound, and its there and won't go away, as I drive it settles out but stays. Doesn't fade away, just keeps making the same noise.

My question is, why is the sound not present when the rear drive line is removed, but comes back as soon as drive line is present. Is it possibly the transfer case and the only reason it doesn't make the sound, is because there is no load on the tailshaft?

Sorry for the long winded post, just trying to figure out my problem and hoping it is not in fact the transfer case in any way. Also, the noise is ONLY present while I am driving in 2wd after 40 mph. Any help is greatly appreciated!!

wauto

Is the front joint on your rear drive shaft stiff or siezed up ? Hows the fluid level in the t-case?

87Heep4wdv

Its not stiff, I can move the yoke when the drive line is out. But its not seized up either. How can I check transfer case fluid level?

neverenuff

could be pinion angle (sye, yes or no? is your xj lifted?), could be loose pinion nut at the rear axle. Could be forward ujoint. If it were the transfercase it would be the output bearing to rear axle... everything is turning inside regardless of 2 or 4 wheel drive(except for front drive shaft out put shaft) low fluid level will not cause a dedicated vibration at a fixed speed. How is your transmission mount ?

87Heep4wdv

I'm assuming u mean slip yoke? And idk. I greased it up and still makes the noise. Its on blocks in the rear, and springs upfront. I think a 4" lift. But either way, barely started making the noise. I drove it home 45 mins. Never made a sound til I got into town. Mount seems fine. Its a rotating sound. Gets louder after 40 mph and stays there, as soon as I let off the gas and coast it goes away. Do you mean the u joint on the yoke when you say forward u joint.

87Heep4wdv

Didn't make the noise when I drive it in 4wd with front wheels only. Noise was gone, so would it be transfer case?

87Heep4wdv

And what do you mean by output bearing to rear axle?

87Heep4wdv

No vibration or shaking whatsoever by the way, just sound.

Silentj

Sub'd since I have the same damn noise and haven't found a fix. I put in a new transfer case and its still doing it. My noise is gone with the front drive shaft out. It's really getting frustrating.

87Heep4wdv

See last night I took out front drive shaft, and I still have the damn noise. So i was thinking transfer case now or trans. Nothing else connected and it makes the noise. My sound, sounds as if its under the rear of the ebrake handle. Have you replaced any of your u joints? I have one u joint left to replace on the rear driveline. The one that goes to the yoke and shaft. If that doesn't work I'm gonna give up trying lol.

wauto

How are your outer axle joints(on the front end, near the ball joints) ?

87Heep4wdv

They seem fine as well. Starting to think its transfer case. I'm going to replace the ujoint connecting to yoke tomorrow. And ills we what happens then. Other then that I have movement when braking so I'm going to check calipers and brackets.

neverenuff

your rear drive shaft has two ujoints one on the slipyoke side and one on the axle side.... you replaced the axle side joint , how is the joint on the slip yoke side? with a 4" lift you should have a slip yoke eliminator installed on your transfercase. How is your pinion angle? is the pinion pointed (within a few degrees) at the transfercase? do you have degree shims installed at the leaf spring perches? the noise could be related to worn out bearings in the tailshaft of your transfercase... is there much movement in the transfercase output shaft (rear axle side)? you stated the transmission mount is fine no cracks or tears in it ?

neverenuff

what I said about pinion angle was only correct with a double cardon style drive shaft. If you still have the orginial slip yoke style drive shaft the pinion angle and the output shaft angle on the transfercase must match or be the same within 1 or 2 degrees.Sorry about the mis-information

87Heep4wdv

I don't have a slipyoke style driveshaft on the rear. Only on the front. The front u joint seems fine no movement in it. The trans mount is perfect. Seems new. No tears and its not seperating or anything. I'll check if the output shaft has play tomorrow.