Tires made noise appear from Transfer Case?

[SwampSurvivor]

First, I have a completely different Jeep than I did 2 months ago! Well, same one as before, but all of the major problems have been fixed! It has a working radio, safe steering and suspension (new ball joints), working 4 wheel drive (new front axle / diff) and no more driveline vibrations (dropped the axle yesterday and got the correct pinion angle) ... on top of that, it rides very nice with new springs!

What was weird is when I was at highway speed, there was a bit of a grinding / scraping noise coming from the transfer case lever. Obviously, it connects to the transfer case. It got worse as speed increased.

Sounded to me like the transfer case chain was stretched and hitting the case. Pretty common problem for NP231.

I have an appointment to get it inspected Thursday, so I was going to have the mechanic look at the noise, a bit of knock from the engine ... or listen ... along with the inspection.

I put on some quiet all terrains as the mud tires are just too loud to effectively hear it.

To my surprise ... the noise went away? I'm surprised but not complaining.

The chain only drives the front driveshaft, and the entire time I was in 2WD. So it's not from power being applied as none was going to the front axle.

The only thing I can think of is there was some sort of reverberation coming through the body and rattling the lever from the mud tires?

 

[jeepman3071]

I've heard a loose chain inside an NP231, and its definitely not a grinding noise. It sounds like a really bad clunking.

If the noise changed with the tires, then I bet your problem was the M/Ts. M/Ts are very loud and vibrate quite a bit. Since the Jeep is a unibody vehicle with little sound deadening, any tire vibrations can be easily transmitted into the cab.

I've had the same experience with worn out A/Ts vs. new and balanced A/Ts.

 

[SwampSurvivor]

We did an experiment with my Jeep and a Wrangler - the mud tires are quieter inside the cab of the wrangler. The body mounts on the Wrangler take up the majority of the humming apparently.

 

[jeepman3071]

Originally Posted By: Miller88
We did an experiment with my Jeep and a Wrangler - the mud tires are quieter inside the cab of the wrangler. The body mounts on the Wrangler take up the majority of the humming apparently.


Yup. My friend doesn't have carpeting in his 2000 Cherokee. It had a water leak from a bad rear hatch seal and the carpet smelled terrible. We removed the carpet and bed lined the inside. His jeep is exponentially louder inside now. His A/Ts sound like Mud Terrain tires on the inside.

 

[Kuato]

New tires = same size, mud tires slightly different sizes causing some rotation of the front driveshaft?

 

[SwampSurvivor]

I don't have lockout hubs so the front driveshaft is always spinning. Front mud tires were the same age, though.

 

[Kuato]

Originally Posted By: Miller88
I don't have lockout hubs so the front driveshaft is always spinning. Front mud tires were the same age, though.


How about the rears? Since the front shaft is always turning, there is something also turning inside the TC; if the speeds were different enough it could make noise.

Case in point: I rented a Dodge Durango with AWD. New tires on one axle, original on the other (25k on the vehicle). Above about 40, there would be a low rumble coming from the drivetrain, which became rhythmic at higher speeds. Same size tires, but different makes and different amounts of wear.