Name that noise!

[Mitch502]

So, I just noticed a sound that has gotten worse (I think). It is a grinding noise. It only happens around 45mph and above, and only sporadically when not on the gas. I noticed it more after I fixed a broken trans mount. My set up is as follows:

2001 TJ
242j transfer case with no linkage hooked up
AX-15 mounted with Novak mount
8.8
All fluids are full
Rear driveshaft was made by me, but never had an issue with it, new u joint, no play
Front driveshaft is not currently in


My first thought was that I knocked the transfer case lever on the case itself. I have it shifted in what would be the 2wd position for a 231, I assume it's the same for the 242. Please correct me if I am wrong... This is the diagram I used.

https://flic.kr/p/YzZKfu

My next thought was that the transfer case chain is stretched. Is there a test for this?

Thanks
Mitch

 

[Mitch502]

Also, when the noise is present, the shifter does not seem to be a stethoscope for it...so I do not think it is the transmission itself.

 

[JeepN95YJ]

A grinding or growling noise coming from the rear axle upon deceleration is often a rear ujoint or a pinion bearing.

Have you had the rear axle apart? Did you have the yoke off? The 8.8 has a crush sleeve for pinion bearing preload. It is possible that the bearing is loose or worn.

That is the first place I'd check.

 

[Mitch502]

I have not taken the rear 8.8 apart. I checked it and it all seemed fine prior to install. U joint is new, so I'll check the pinon bearing for play/noise next chance it's not raining.

 

[BigDaveZJ]

Sounds pinion related to me as well.

 

[BCobe]

Post up a video! That might help determine the sound.

 

[Mitch502]

I pryed on the pinon last night, and it had to play...didn't get to jacking it up yet. I'm starting to hear it when I'm rolling to a stop in neutral...I'm REALLY learning towards something with the transfer case based on the sound. I checked the case and it was full of fluid...but it sounds very close to a time when all the fluid leaked out of a transfer case on my ZJ...I will post up a video if I can get one that actually sounds right...

 

[BCobe]

The sound from the pinion bearing could reverberate and sound like its coming from the transfer case.

 

[Mitch502]

The sound from the pinion bearing could reverberate and sound like its coming from the transfer case.

I've always considered bearings would make noise all the time...unless specific pressure/torque was applied (like turning back and forth to have wheel bearing noise go away)...with that logic, I would think that the noise would always be there when off the gas? not intermittent?

 

[BCobe]

I've always considered bearings would make noise all the time...unless specific pressure/torque was applied (like turning back and forth to have wheel bearing noise go away)...with that logic, I would think that the noise would always be there when off the gas? not intermittent?

Only reason that I am stating pinion is because you had play, which could mean the pinion preload is off or you have a bad bearing. Also, if your pinion preload is too loose it would make a sound when you accelerate due to the pinion kind of rocking back and forth in the race offsetting your clearance to your ring gear.

The sound might also not be audible due to engine noise or other road noise.

A lot of variables honestly. I know I have a bad pinion race but it sounds like its coming from the front.

 

[JeepN95YJ]

The reason the pinion makes noise on deceleration is because the loose bearing allows the pinion to move back toward the ring gear when you let off the gas. When you are accelerating or driving the load on the pinion forces the pinion away from the ring gear.

If the bearing is loose enough you will likely find the pinion actually grinds a mark onto the carrier. it isn't the bearing you are hearing, it is the pinion and ring gears grinding on each other..

 

[Mitch502]

Thanks for the info guys. I'm looking at getting a different 242 because I want to put a SYE and only have the tail cone'd 242 right now...as part of the plan anyways (not related to this noise, or trying to fix it)

Can anyone confirm what position is 2wd for the 242? Should the lever be "up" as far as possible, or "down" as far as possible?

I'm going to HOPEFULLY get a video of it today and see if I can figure anything out.

 

[JeepN95YJ]

I just took this pic of my 242 shifter. This is 2wd. Looks like all the way up is correct.

 

[Mitch502]

I just took this pic of my 242 shifter. This is 2wd. Looks like all the way up is correct. View attachment 418534

Thanks so much for the confirmation... Front driveshaft should be installed tomorrow if it's not raining, and that should help me with the noise

 

[BCobe]

Any updates on the noise?