Drivetrain Noise During Acceleration

This noise is noticeable in third, fourth, and fifth gears under moderate to heavy acceleration (such as merging with traffic or driving up a fairly steep hill). It sounds somewhat like a rattle or vibration but is not a clunk, shudder, grind, or whine. The noise occurs at rpms below 2000 and is pretty much gone by 2500. The lighter the acceleration, the less the noise and the lower the rpm at which the noise disappears. The noise is not present in neutral or on deceleration. However, under heavy acceleration, when the clutch is depressed, the rattle continues very briefly until the driveline load changes over to coasting. The noise / vibration can be felt through the transmission gearshift lever.

Noise/vibration is occuring while transfer case is in two wheel drive with front hubs unlocked.

Any ideas as to cause and seriousness? Does this sound like transmission countershaft bearings?

This is a 98 XJ with 4.0L, AX15, and 231J.
Dana 30 front differential with Warn front lock out hubs and Eaton ELocker.
Dana 44 rear differential with Eaton ELocker.
4.56 gears and 35x12.50/15 tires.

The search links I looked at didn't seem specific to this problem. Thanks for your help.

Could be driveshaft rumble--when you goose it the pinion will jerk around and can cause some binding. Do you have an SYE?

Good thought. Have an SYE but haven't installed it yet; going to put it in when I install my doubler. This would also explain the slowly increasing volume of the noise and how often it occurs. Thanks

Anyone else?

Check your engine mounts and transmission mount.

Worse when under load those are two things I look at early on.