Rumbling/grinding noise

[steph74]

When I let go off the gas, in 4th or 5th gear mainly, I can hear this kind of rumbling / grinding noise coming from the back.

I don;t know if it is there all the time ... it maybe covered by the noise of the engine....
Seem to occur more when I go downhill and that the jeep is just "free" wheeling (I have a manual).

This is my plan of action so far
1/making sure the rear breaks are adjusted properly or that at least they are not dragging
2/checking the wheel bearings
3/it almost sound like a pump that is missing or something.... could it be the fuel pump ?

I know it is difficult /impossible to diagnose a noise in a forum, but what do you guys think it could be ? Or at least what are typically making noises in the rear that I should check ?

[Weldmen]

U-joint or carrier or pinon bearing?

[4.3LXJ]

Steph, does it do it going down hill in neutral?

[steph74]

Good question, I will check that.
Eventhough I guess that would pin point a drivetrain or tranny problem.

[alwaysxj]

get under the jeep and push up on the drive shaft if it has a lot of move ment it might be the u joint. my 88 made this noise from the t- case when i would let off the gas and it turned out to be the u-joint was moving around to much.

[uberxj92]

mine makes a noise like a machine gun...it has little pits in the ring & pinion gears from a catastrophic failure in the past.

[saar]

Do you have a LSD diff?
(Dana 35C w/lsd)
If you do, you may want to verify that the lsd discs are not broken.
Saar

[ohuwill]

Sounds exactly like the noise my 96 is making. i too have a 5 speed and had a brand new clutch put in. 6 months later I have this grumbling grinding noise comming from the rear i thought. well when the new clutch was put in, it was put in with the old slave cylinder. several mechanics have checked this out and all say its the slave cylinder. at least on mine it is. hope this helps.

[steph74]

wow it sounds to me I have open a can of worms ;) lol
I am not experienced enough to check all these things, so I will do it slowly, proceeding by elimination.

Fluid level checks;) everything is good so far
Drive shaft play... check... it is moving a little bit but once again my lack of experience doesn't allow me to say it is bad or acceptable or normal...

I have tried it going down in neutral and I kid of ear the noise but it is faint.
I have tried the foam cup on the shifter that matt recommended.... brings all kind of noises but once again I do not know if they are normal lol

One thing is sure, is that it still drive and not really a DD an there is still snow up in the mountains so I do have at least a couple of monh more to figure out something

[steph74]

Do you have a LSD diff?
(Dana 35C w/lsd)
If you do, you may want to verify that the lsd discs are not broken.
Saar

I am pretty sure I don;t have that ....
But just in case, how can I figure it out ?

[4.3LXJ]

Steph

I wouldn't worry too much about the LSD. Very few XJs have them and if the discs were bad you probably wouldn't notice it unless you go around a corner. The reason I wanted you to do the neutral test is to narrow down the possibilities. If the noise stayed the same, then I would say wheel bearing. But if it mostly dies down but is still there, I will say ujoints. Since you have a little play, tell me more about it. Also, when ujoints get dry, they can get some orange dust around the seals.

[steph74]

Thanks Steve

So I have been a little farther ;)
It seem that the rumbling sound disappear when I press the clutch down and comes back when I release it ...

Now describing noises is difficult but it almost sounds like a faint muffler noise actually.... anyway I keep on tack

I will try to inspect the U-joint more closely that the little snow we got yesterday is gone ;)
Stay tuned;)

[4.3LXJ]

Thanks Steve

So I have been a little farther ;)
It seem that the rumbling sound disappear when I press the clutch down and comes back when I release it ...

Now describing noises is difficult but it almost sounds like a faint muffler noise actually.... anyway I keep on tack

I will try to inspect the U-joint more closely that the little snow we got yesterday is gone ;)
Stay tuned;)

The clutch associated noises. Are you moving or coasting in neutral when this happens, or are you in the driveway?

[steph74]

moving ....
so if I cruise and stay in gear and let the jeep free wheel by pressing the cluthc then the noise disappear....
the noise is also there when I have my foot just a little on the gas acually but is gone when I press the gas pedal (maybe I con;t hear it)

Anyway still exploring.... the U-joints are greased OK and they really seem tight.

Now if I grab the shaft I can rotate it while car is in park, engine off and in neutral ...
If weather allow I will try to take a small video or pics tomorrow maybe it is all normal and I am just worrying too much ;)

[4.3LXJ]

moving ....
so if I cruise and stay in gear and let the jeep free wheel by pressing the cluthc then the noise disappear....
the noise is also there when I have my foot just a little on the gas acually but is gone when I press the gas pedal (maybe I con;t hear it)

Anyway still exploring.... the U-joints are greased OK and they really seem tight.

Now if I grab the shaft I can rotate it while car is in park, engine off and in neutral ...
If weather allow I will try to take a small video or pics tomorrow maybe it is all normal and I am just worrying too much ;)

Does it happen in any gear?

[prcjeep]

Hey Steph... My 96 5 speed did exactly what your description sounds like... under power you cant hear it so much do to the u joint having pressure on it and it not"wobbling" around in its mount but when coasting you can hear it due to lower engine noise and it also does not have constant contact on one side of the ujoint from being under power and it will wobble due to whatever play it has from being worn down. The picture below shows what mine looked like when i took it out to replace it. After replacing it, the noise was completely gone. Hope this info helps... Change your ujoint or both on the rear shaft to be safe, mine was the rear one on the rear DS... they are about 10 dollars and they are not too difficult to change.

http://i936.photobucket.com/albums/ad210/prcrawfo/ujoint.jpg

I also wanted to add that I put a new clutch in mine when i did my motor swap about 15000 miles ago. I didnt change out my slave cyclinder and havent had any problems from not changin it with the new clutch installed

[ralphy]

Steph, I'd have to agree with the others and say the u joints, or maybe the pinion bearing on the rear diff. good luck with it.:thumbsup:

[steph74]

thanks guys or helping me pointing in this direction.... I will get too it ASAP and let everybody know if that helped (right now there is other issues due to my little hill climbing attempt this week end ;))