Ford Ranger 3.0 Litre Turbodiesel Manual Transmission, 4x4.
Ford Ranger made a single brief spontaneous grinding noise while already engaged in 3rd gear without any action applied to the clutch or gear lever. Vehicle was accelerating up a mild slope.
The same occurrence happened in 5th gear after completing an incline as the slope flattened and I eased off the throttle. Torque was still moderately applied as I heard the same grinding noise twice. No interaction was made with the gear lever and clutch during noise.
I very recently bought the vehicle second hand.
The transmission is patched up with gasket sealant.
Transmission and rear diff oil levels are full, but oil is old.
Vehicle is 4x4.
During idling, a squeaky rubbing noise originates from the bell housing. Noise disappears when slightly disengaging the clutch.
Also consider the grinding noise to come from sources beyond the gearbox.
What could be the cause of the above grinding noise observed during 3rd and 5th gear?