Whining @ 1800 RPM

[oworm]

Had the new engine in about a week now. I got the clutch replaced also while it was pulled. Im noticing a whining (faint rumbling) noise at around 1800 RPMs in all gears. It goes away below and above that speed. The only other thing I got done was a change in transmission oil (4 speed T19) Ive heard this noise before on rear wheel drive vehicles. Back in the UK the old black hackney Taxi cabs would make this noise sometimes. Any ideas what it might be?

Its really prominent in 4th gear traveling at 45mph but if I drop below or go above that speed it disappears.

 

[Diesile]

U joints??

 

[OLDBULL8]

Does it have a center support bearing on the drive shaft?

 

[Goofyexponent]

Only at 1800 RPM? Vicki whines ALL the time when we gotta take the truck.

 

[oworm]

Does it have a center support bearing on the drive shaft?

Yes............The support itself is intact and the rubber bushing looks and feels good with no excessive free play. I actually asked the shop to check all the u points and supports when they swapped out the motor and he said it was fine