Topic: Drivetrain Whine

[JC93YJ]

My 93 YJ just started making a whining noise out of the blue, kind of like gear whine but not all that loud. I crawled under it and checked all the fluids and the tcase was a little low, it leaks, so I filled it back up with at most a quarter of a quart. While I had it on jackstands I ran through the gears and it was silent. Drove it around and it was still there. It starts whining at 20ish mph and makes a deeper whine between 35-40mph. But it’s a quite whine, almost like aggressive mud terrains. For ha-ha’s I put it in 4HI and drove down the street and it made a little noise under 5mph and was then silent up to 30mph (that’s as fast as I went), and when I let off to slow down it whined like before, but only slowing down. All the u joints are okay and the rear pinion is tight. I noticed the passenger side wheel doesn’t spin as free as the drivers side, but I figured it was just the pds dragging on the rotor, or the wheel bearing might be on the way out, but I wouldn’t think it would make this much noise. Anyone have any ideas?

Joe

[Jeffy]

When you had it on jackstands did you try 4wd?

[JC93YJ]

No I didn’t, I didn’t think of it at the time. As soon as I put it in 4HI it was silent, and then when I let off to decelerate it whined. I’ll have to put it back up on stands and try 4HI again and see what happens. I spun the front driveshaft by hand today and it turned smooth, minus what I would assume was some mode ring play. The u joints and pinion on the front end are tight. 

[Jeffy]

Have you localized the sound any?  Front vs back left vs right?

If I had to take a while guess, I'd say it's a bearing.  Could be a pinion bearing.  Leverage and angle changes from forward to reverse.  The front driveshaft shouldn't turn when in 2wd unless you have a LSD or locker in the front axle.

[JC93YJ]

It sounds like it’s coming from the passenger side. I noticed a slow rythmic noise as well, like when a tire makes noise, so I’m thinking maybe it’s towards the outside of the axle. I’m hoping it’s not the pinion, but I was told even if it was to keep oil in it and limp it along, not sure how much I believe that. It’s just stange because all the fluids are good and everything is tight and I don’t beat on it and it’s never been off road since I got it.

[Jeffy]

I don't think it's the front pinion if you're hearing it in 2wd.  The driveshaft doesn't turn on a stock YJ in 2wd.

[JC93YJ]

I spun the front driveshaft by hand and it turned nice and smooth with no immediate weird noises, not that I would hear anything turning it that slow. I’ll try and get it back up on jack stands today.

[JC93YJ]

https://youtu.be/wg0SB-f7Ads
Here’s a video of what it’s doing. I ran through 1st to 4th, right at about 50-55mph it started making a slow rythmic noise, you can just barely hear it on video. At the end I let off and was decelerating and then I put it in neutral and let it coast.

[Jeffy]

Are you sure it's not your tires?  It's definitely speed related and not RPM related.  Around 25 mph is when air resistance starts to come into play and that's when tires start to make noise.  I can hear a whine around 20 then it goes all the way to 50 where it seems to flutter at 55 as your trying to hold it there.

You'll want to try to localize the sound front or rear and left or right.  This is kinda tough to do alone though.  Taking the top off might hellp.

Also the shift up light is throwing be off.  On my '92 it's in the left square not the center.   

[JC93YJ]

I wish it was the tires, but I think it’s load based. If I give it gas before it gains any speed I can hear the whine change. I think I might have heard a light pop or two going around a corner amiss all the other normal squeaks and rattles, could the apider gears have maybe taken a dump?

Perks of a 93: everything changed 

[JC93YJ]

Ignore the popping comment, that was the exhaust bouncing off the skid pan. I just spent ten minutes driving around in a parking lot trying to make it pop again and I couldn’t do it for the life of me. When my friend blew the spider gears out of his Grand Cherokee, it sounded like someone was breaking a 2x4 under the Jeep everytime he tried to take a corner. Or go straight.

[Jeffy]

If you rev'd it and it changed then I might guess something like the idler pulley.

[JC93YJ]

...if I’ve been driving around with a blown up idler pulley or something I’m going to feel like an idiot. 

[JC93YJ]

I listened to all the pulleys this morning and they all sound good. That pop came back, I was making a left turn over a small speed bump slowly and I heard it come from the passenger side, sounded like the front wheel. I’m wondering if the wheel bearing I think took a dump on me is causing the noises I’m hearing.

The other day when I had it on jack stands I spun the rear tires by hand and they both turned quiet and smooth with no clicking, popping, or skipping like blown spider gears would. I could only make the noise going over a speed bump and turning left, it won’t do it going right.

[Jeffy]

Usually you'll feel a gritty bearing when you try to spin it by hand.  Jack it up and see if there's play and if it feels gritty.