Here's why:
* Gear Engagement: Gears 1, 2, 3, and 5 all utilize different sections of the input shaft within the transmission. 4th gear often uses a different gear set or a different path through the transmission, hence the absence of noise in that gear.
* Bearing Noise: A roaring sound is often indicative of a bearing problem. When the input shaft is spinning (which it does in those gears), faulty bearings will produce a noise that increases with speed. The fact it's absent in 4th gear points towards a specific area of the transmission using that shaft, rather than a general transmission fluid or differential problem.
It's crucial to take your Jeep to a mechanic immediately. Driving with bad transmission bearings can lead to complete transmission failure, leaving you stranded and incurring significant repair costs. Ignoring the problem could also cause further damage to other transmission components. The mechanic can diagnose the exact cause of the noise and recommend the appropriate repair.
