Interesting (suspected) T-Case Problem

[jmlee44]

I have a bit of an interesting noise coming from I believe the transfer case.

Here's the story:
Stared out that a strange metallic noise would emit from the transfer case / transmission area (right under the shifters). The closest thing I can relate the noise to is if someone put a small diesel engine right under the floorboards. It would get louder and softer with changes in speed. The thing is, it seemed intermittent. Once it started it would continue until the jeep was parked overnight - but it wouldn't do it every trip.

Now:
It has been about a week or two since first started hearing the noise. Now it is a daily companion. Here is what I have tried:

If you put the t-case in neutral and idle the jeep in a higher gear (makes the noise louder) you will hear a moan and an intermittent pinging sound (like the sound of two monkey wrenched being tapped together). It will make it in every gear, even reverse and lower gears if you get the revs up enough. I get the noise in 2 Hi at any speed over about 10mph.

Here's the interesting thing - I have a manual disconnect for the front axle - so if I leave the front disengaged and run the jeep in 4HI - sound goes away.

I hear alot of problems with t-cases and the chains and gears - but most of those parts aren't moving when it is in neutral - and if 4Hi makes it go away....

Could it be an adjustment or something fairly simple to fix if I pull it out of there and open it up.

Thanks and good luck

 

[jmlee44]

Sorry -

91 YJ, 2.5, ax5, np231, 120K +/-

 

[jfrabat]

have you opened the TC to take a look inside? You can just take the rear part out and do a quick visual inspection of the chain... You'll have to replace the fluid, but it may be worth checking it out.

 

[Bounty__Hunter]

My first thought was the throwout bearing going out, but the 4hi with the front axle disconnected kinda threw me.

What happens when in 4hi and the front axle disconnect is engaged?

Oh ya, welcome to the Z. Where are you located, in case somebody here with 231 experience is close to you. I rebuild them pretty often.

 

[jmlee44]

I haven't opened it yet.

Yea I pretty much ruled out the transmission (at least the front half of it).
I don't get a noise with the clutch depressed, or with the clutch released in neutral.

It has to be something that is turning only when the trans is in a gear and clutch is out. So maybe on the output side of the trans or in the T-case.

The 4hi trick made me think t-case - but if it likes to be in 4hi, then that would imply that the chain and drive gears inside are likely okay.

I haven't had it in 4wheel with the front axle locked at speed - actually only used low recently to get down an embankment and then was back on pavement. I didn't notice any noise, but I was also more concerned with the descent at the time.

One more detail - as I said the noise changes with the jeep's speed. Even if I press in the clutch, or put it in neutral entirely, it will still make the noise, matching the vehicle speed - not the engine speed..

I'm in San Antonio, TX

 

[mud4feet]

Pardon my stupidity, but have you checked all the u-joints?

 

[jmlee44]

U-Joints wouldn't cause a noise idling with the t-case in neutral.

 

[Bounty__Hunter]

Does it make the noise while revving the engine with the transmission in neutral?

If it doesn't, but does make the noise with transmission in gear and transfer case in neutral, it's time to rebuild the transfer case.

I would drain the transfer case and inspect the fluid closely, looking for bits of brass and/or plastic. It's very common for the plastic bads on the range and mode forks to wear out due to improper maintenance.

 

[currupt4130]

My first instinct was output bearing on the t-case.

 

[mud4feet]

U-Joints wouldn't cause a noise idling with the t-case in neutral.

Like I said, pardon my stupidity.........I need to read more carefully. Wish I could help.