2001 5R55E transmission making intermittant horn-type sound - thoughts?

[neutronranger]

My 2001 4WD (4.0L 6-cylinder) automatic transmission (162,000 miles) has been making an subtle, intermittant, horn-type sound (French horn or trombone) during the last 6 months.
I believe it would be a 5R55E transmission.
I hear the sound most easily when parked (not in gear) and the engine is running.
I had the transmission flushed and fluids changed about 6 months ago (5000 miles ago).
I've not noticed any shifting problems.

I took the Ranger it to a trusted local shop and they said that sound is a pump inside the transmission.
My experience with this shop is they don't push repairs that aren't necessary and they are fair with pricing.
They said it is not in imminent danger of failing, but it will fail eventually.
They said this is a common failure of this particular Ford transmission.
Since the transmission has to be removed to replace it, the prescribed remedy is to replace the transmission with a remanufactured transmission.
Remanufactured transmission is $3000. Labor to remove old and install new is about $1300.
Total $4300.

Does this all sound familiar and in line with reality?

Thanks!

 

[neutronranger]

I made the decision to commit to the transmission replacement.
The remanufactured transmission arrived at the Aamoco shop today and I dropped off the truck.