Howdy folks, I'm new and have a question I'm hoping you guys can help with. I have a 1999 TJ with a 4.0, AX15, NP231, and Ford 8.8 rear. 250k miles, but the transmission isn't original, unknown mileage (from a YJ). I've recently been having what sounds like a bearing noise from either the transmission or the transfer case. It sounds like something is full of rocks. It only happens above 50 mph. Happens whenever I push the clutch in or put the transmission in neutral; if I decelerate with the transmission in neutral, it makes the noise until I slow down to about 40 and then it goes away. It either does not make the noise going through the gears with the tcase in neutral, or I cannot hear it over the engine. It also does not seem to make the noise at all until everything is warmed up.
So about two months ago I noticed a very similar noise, but much worse, after a couple hours on the expressway. At that time, it would also make the noise when decelerating in gear. I limped home and believing it to be the tcase rear output bearing, rebuilt the transfer case. All the bearings and seals in the tcase aside from the planetary bearings are brand new, and so is the ATF. Both tcase output bearings were worn out when I pulled them.
I also previously had a bad driveline vibration which turned out to be the tcase mounting bolts loosened up severely. Like, "tcase about to fall off when I checked it." That is now resolved, but I didn't think to check that for a couple years, and drove with bad vibration for a long time, making me wonder if I damaged the transmission output bearing.
So now I have all new tcase bearings, and the noise is back, though not as bad as it was. I'm not sure now if this is a transmission noise, a tcase noise, or even a rear differential noise. Any advice is very welcome.
So about two months ago I noticed a very similar noise, but much worse, after a couple hours on the expressway. At that time, it would also make the noise when decelerating in gear. I limped home and believing it to be the tcase rear output bearing, rebuilt the transfer case. All the bearings and seals in the tcase aside from the planetary bearings are brand new, and so is the ATF. Both tcase output bearings were worn out when I pulled them.
I also previously had a bad driveline vibration which turned out to be the tcase mounting bolts loosened up severely. Like, "tcase about to fall off when I checked it." That is now resolved, but I didn't think to check that for a couple years, and drove with bad vibration for a long time, making me wonder if I damaged the transmission output bearing.
So now I have all new tcase bearings, and the noise is back, though not as bad as it was. I'm not sure now if this is a transmission noise, a tcase noise, or even a rear differential noise. Any advice is very welcome.
