Hissing noise - Jeep Wrangler JK.

[JKBall]

Hi everyone,

In short, my Jeep Wrangler JK has been making, what I describe as a hissing noise, for the past 5/6 months. During that time I've had the issue/noise listened to, inspected by and engine parts removed and reinstalled by multiple mechanics and “experts” in the hope to specifically identify and fix the issue.

My Wrangler JK is a 2010, 3.8-litre petrol, 6-speed manual and has travelled 49,000kms.

As I said above, the noise sounds like a hiss and is most noticeable when driving in second gear but is also noticeable in all gears but most predominant in the lower gears. I'll say at this point, I'm confident it's mechanically related, it's not a hissing/leaking pipe or tube. However, within the past 2 weeks, the noise also appears while in neutral and stationary but goes away when the clutch is pressed but returns when the clutch is not pressed.

The major work I've had done to try to locate and fix the issue is as follows:

- Gearbox removed, taken apart and inspected by 360 Gearboxes and Diffs. Who informed me that there is nothing wrong with the gearbox. The gearbox was hot washed and the seals and bearings were replaced when reassembled.

- A new clutch installed, when the gearbox was reinstalled.

360 Gearboxes and Diffs also suggested to check;

- Check Tailshaft universal joints.

- Check your rear diff oil – if it has metal contamination or if the flange has play, you have found your problem.

I had the tailshaft universal joints and rear diff oil checked. Which were deemed fine.

The Jeep dealership mechanic who reinstalled the gearbox and new clutch originally advised a second hand or a brand new gearbox should be installed, he then claimed it was the bearings within the gearbox that were/are causing the noise/issue after the gearbox came back from 360 Gearboxes and Diffs, who disagreed that it was the bearings causing the noise/issue.

Then when I picked up the Wrangler on the 23rd of April, after the new clutch had been installed and the gearbox reinstalled he then claimed he had done some research online and spoke with a Jeep Australia technician who explained to him that the hissing noise was normal for a Jeep Wrangler, particularly in second gear. As the second gear has a concave design and the other gears, including reverse, don't. So that's why second gear hisses/makes the noise the most... I think this is absolutely rubbish.

So, in your experience with Jeep Wrangler JK's, have any of you come across a similar issue? Does the second gear have a concave design? Do you know what could be causing the issue? If so, is it normal and nothing to be concerned about or is it something to be concerned about and what do you recommend to fix the noise/issue?

I would appreciate constructive responses, not comments about ignoring the noise, turn up the radio or it's a Jeep, it's meant to make odd noises...

Thank you.

[Nanook]

Maybe you should mention what year your model is, what motor you have and the kms you on it.

That would hopefully make it easier for someone to identify.

[Banshee]

OK. He updated with 2010, 3.8 manual.

You say it goes away when the clutch is pressed. Moving or stationary? No noise when moving & clutch in?

[HamishW96]

Did they do a pilot/spigot bearing when they did the clutch....

[JKBall]

Originally Posted by Banshee

OK. He updated with 2010, 3.8 manual.

You say it goes away when the clutch is pressed. Moving or stationary? No noise when moving & clutch in?

Hi Banshee,

When moving/driving the hiss/noise goes away when out of gear but returns when in gear, particularly, being louder or more noticeable when in the lower gears, specifically second gear.

When stationary and in neutral, the hiss/noise goes away when the clutch is pressed in but the hiss/noise returns when the clutch is not pressed and the Jeep is in neutral.

I haven't tested if the hiss/noise is present when moving and clutch in. Do you mean moving, clutch in and in neutral?

[JKBall]

Originally Posted by HamishW96

Did they do a pilot/spigot bearing when they did the clutch....

Hi Hamish,

I'm not sure if the mechanics inspected the pilot/spigot bearing when they replaced the clutch. What do you suspect, it could be loose or damaged?

[Hayesio]

Hi mate.

Try this: with the car stationary, in neutral, engine running, leave you door open and press the clutch in and out, in and out. Listen for the noise. Or better yet, get the missus to do this while you get down to the clutch housing and listen.

If the noise goes away when pressed in but comes back wthen released - its almost certainly the release bearing. This is a relatively common problem for JK's petrol and diesel alike. Mine, diesel, does it, and yes it's annoying. But don't be too alarmed, its not imminent failure - mines done it for 3 years now.

What makes the sound is when there is almost no pressure on the release bearing from the clutch fork against the spring/pressure plate in combination with the bearing having a little bit of play in it. The balls are able to "rumble" around a little bit. This "rumble" causes vibration through rest of the bearing assembly and against the clutch spring - which makes it louder. As soon as you apply pressure, the inner and outer races are compressed together, balls are aligned into the races and walla, no noise.

I'm betting they didn't change the release bearing when they did the clutch - dealerships are know for tight-a*sing on this.