Transfer case noise after 30 minutes on road

[goldjeep99]

Hello Forum... my first post...
I have a JGCL 99 V8 4X4. 103,000 miles. Symtom: after driving on highway for 30-40 minutes (warm gears and trans oil) when coasting, not under load, there is a very loud clink-clink and grunting noise underneath (I can hear it against the highway divide). There is no noise when cold or driving short distances in city.
Took it in to dealer and technician diagnose is t-c chain noise, but no need to change now. Took it to Cottman transmission and diagnose is probably the viscous coupling inside the t-c.
Does anybody have experience knowledge of what it can be?
How bad can this noise be? Can it fail? Catasthrofic potential? Please help. Thanks.
Gold

[bgmoss28]

It may be obvious, but it sounds like there's something loose in the tc. When the oil is cool, it's too viscous to let whatever it is bang around. After it heats up, then your problem starts.

A couple of comments about the chain: In my mind, there are two possibilities if the problem is the chain. First, the chain may have broken but not all the way through. The section where it's broken is flopping around and hitting something. This could be major. Not only is the chain weaker now, if it's hitting something else, that's also damaged. The other possibility is that there's slack in the chain. Slack by itself shouldn't be a big deal, but what is concerning is where that slack came from. The only thing I can come up with is damage to something else. These chains aren't supposed to go slack, so if this is the problem, there's probably something else wrong in the tc.

It's intriguing that the noise is only there when coasting. I'm no expert, but it seems logical that the problem is slack. When it's not under load, things loosen up and provide your clank. When you hit the gas, the chain is under load and tightens on one side according to the rotation of the drive shaft. The other side is still loose, but that would mean that the point of contact is on the tight side.

Are you sure the problem is with the tc? I had a constant thud proportional to the speed of the wheel. It ended up being a problem with the brakes, the caliper, I think. Other possibilities are bad bearings, bad axle u joint, bad cv boot etc.

Hope this helps, and that everything's right.

[bgmoss28]

I meant to add the link to a great website I found. I'm sure many people here know about it, but I found it very informative.

www.wjjeeps.com (home page)
www.wjjeeps.com/tcases.htm (transfer cases)

[jeeperphil]

could be the chain is stretched. when it gets old or has seen alot of off road abuse it can stretch. when hot it expands more and slaps the inside of the case. I've seen evidence of this in several cases with marks inside the case where the chain runs. It's acually a common problem.

[goldjeep99]

It really does sound like the chain streches after it is warm. If I drain oil from the t-c I guess I would find metal cuttings in it???
How bad is this problem? Can I go on driving for a while?
Thanks,
Gold

[jeeperphil]

just take it easy so it doesnt jump the teeth and strip those. you won''t always see shavings in the oil becaause the chain dents the case, not cutting away at it. It can crack the case if it is really stretched. But it will jump and bind the case if its that bad. if you can't open and do it yourself it sounds like you need see a mechanic. one other possibility is the oil picup tube is loose and slapping around. no matter what it can lead to problems.

[goldjeep99]

My guess is that it is not the oil pump suction tube since the noise only occurs when decelerating. (I wish it was the tube, though). It does sound more and more like it is the chain... the slack when expanded because of the heat. Last night, after driving for a while and with the noise very loud y parked the JGC and tried moving the front drive shaft and was too hot to the touch... I thought it was strange!
Gold

[goldjeep99]

I found the problem... But not without a little fiasco!

I took the GC to Cottman Transmission. The guy there convinced me to spend $275 to open the T-C for diagnostics, eventhough I told him I thought the noise came from the front driveshaft.

Cottman opened the the T-C and called me to tell me that although nothing was visibly wrong, they recommended changing out the chain and the coupler... for the mere sum of $2100!

I told them no way and to put it back together. and asked again if they had inspected the bearings... we went outside to the car, which was raised. Looking closely at the the front driveshaft I noticed the rubber protection on the T-C side was gone and the beraings were wasted.

That is what caused the noise.

Cottman is still trying to convince me to spend the $2100!

Can you believe that!

I still need to put in the new shaft... which seems like a lot of money!

Thanks to all for your valuable insight.

Gold

[jeeperphil]

good job!! 2100 is a lot for any tc work. i can buy a new one here for around 2400 with factory warrenty.