My '88 SWB Montero is making a chirping sound that appears to be coming from the rear end or driveshaft. It starts when the vehicle warms up and increases in speed as I go faster. I jacked up the Rear and checked but no noise. After I put it back on the ground and drove it, it made the noise again. I'm concerned about driving very far until I figure it out. Thanks in advance for any help.

1988 montero
31X10.50X15 Pro Comp A/Ts on 15X8 Rock Crawler 97s
Weber conversion with carter fuel pump. Roof rack in progress.