Transfer case noise

[5speedcobra]

Hey,

Just got my 98 XJ. It make a nice noise while driving from the transfer case. It get worse when accelerating, and gets way better when decelerating.  I thought the  noise is directly related to the speed of the jeep, but when I switch the transfer case into N, as the cars rolling at about 20, and I put the jeep in gear and keep the revs up a little, the noise is directly tied into the speed of the transmission output shaft.

I don't know very much at all about transfer cases, especially in regards to what /where it actually disconnects I put t-case in N. All I know so far is that with it in Neutral, the noise follows the transmission speed, with it engaged in either 2 or 4by , it follows the vehicle's actual speed.


Any ideas what it could be? My simple brain is thinking transfer case input shaft bearing, or may be chain ( if that even spins with it in N? 

[binare]

You didn't mention fluid... Checked it?

[morerpmfred]

If it sounds like angry squirrels, then could be cv joint in front driveshaft.

[JENSSEN]

I had a similar issue swapped tcases only to find it was the front gear set, put it on stands run it in gear and make sure you indentify the location. Diagnose the $#it out of it before tossing parts at it.

[5speedcobra]

Just replaced all the fluids. I just did more driving and here are more accurate details:
-sounds grows with vehicle speed increasing
-Worse under acceleration when cold.
-worse under deceleration after warms up.
-sound stops  when jeep is stopped or when T-CASE in N and foot on clutch
-sounds comes back if put it in a gear and release the cluth while T-CASE  is in neutral, no matter if car is stopped or moving, and the sound's directly related to speed of transmission output shaft speed.

Front u joints are good, I just changed one. The sounds kinda like grinding, and it's coming right by the gear stick.

[vantagetes]

So it's a problem with your clutch or transmission, or tcase input shaft then. If you can make it do it while the jeep is stopped and the transfer case is in neutral it's not an output shaft.

[JENSSEN]

May I guess throw out bearing?

[vantagetes]

May I guess throw out bearing?

That's what I thought but wouldn't that make noise when the clutch pedal was in not out?

[5speedcobra]

I did a bit more driving and thinking last night and I don't think it's possible for it to be clutch related. The noise doesn't change with rpm, but rather with the speed of the transmission output shaft. And whether or not I press the clutch there is no change in the sound. Except for when the transfer case is in Neutral, at which point  the transmission's input and output shaft along with the Tcase input shaft will slow to a complete stop. BUT,  the pressure plate bearing would still be spinning.

My thoughts now are, is it the Transfer Case input shaft, or the transmission output shaft? Are one or the other more prone to going?

[vantagetes]

At this point I think splitting your transfer case from the transmission would yield the clues you need. There's either going to be play in the output shaft or the input. With the tranmission in neutral there's absolutely no noise clutch in or out?

[5speedcobra]

 with the transmission in neutral, as long as the cars moving and the transfer case is not in N it's makes noise no matter what.
I got underneath it today, and had it going in 4X4...the noise is deff coming from the transfer case! It almost sounds like the chain! Is that possible?

[vantagetes]

Very possible they stretch and wear out after time but if it makes noise when the jeep is not moving and the tcase is in neutral that's not your suspect.

[5speedcobra]

when the transfer case is in Neutral, it only makes noise  if I have the transmission in gear with the foot off of the cutch. Whatever that noise is tho, it's deff coming from the transfer case area.
When I remove it, do I need to also remove the cross member? Also, do I need to drain the oil from both the transfer case and transmission, or just the transfer case?

[vantagetes]

You'll need to put a jack under the transmission as the cross member actually holds up the transfer case, transmission AND engine. There is a VSS sensor to unplug on the back by the rear drive shaft, and the 4wd switch just foward of that. I think the wire for the rear O2 sensor is also pop clipped on  a bracket. From there disconnect the breather hose on top and just to the left of where the tcase connects to the tranny.

Now you are ready to start disconnecting components. Both drive shafts need to come off and the shifter linkage. To do this you can either take off the two bolts or use a prybar to pop the linkage out of one of the plastic clips. Now double check to make sure the weight of the transmission is supported and drop your cross member. Now all you have left is 4 bolts holding the tcase to the transmission, you can lower the jack a bit to give you access to the top bolts if needed. The tcase is pretty light so you can bench press it down onto your chest and slide out from under the jeep with it on a crawler. The tranny output and the tcase input both have their own seal so if you have oil in there one of the two is leaking suggesting a worn bearing.

[5speedcobra]

That' s very very good to know! Now that I think about it, there's actually oil splashed onto the under-body right where the transmission hooks up to the Tcase. Thank you for the info, I'm going to swap it this weekend. Does it go back in relatively simply ( like putting a transmission on an engine) or are there any special tips or tricks?

And when I put it back, do I need to apply any sealant between the Tcase and transmission?

Cheers,