Re: front end noise
Your jeep is most probably quadra drive or quadra trac II and uses the NV247 T-case. Using a thicker fluid in there then the one advertised by jeep sounds foolish. The fluid has a special jeep P/N, but is just Mobil 424 fluid.
A bend propeller shaft could cause a lot of vibration, but i would not expect it to appear during braking only. Check the propeller shaft joints ( CV or U joints) for play. Eventhough removing the propeller shaft solved the problem, it will not 100 % guarantee that the problem is the shaft itself. There could eventually be a problem inside the differential or the T-case. A too far stretched chain inside the T-case for example caused strange noises with other members jeeps before.