BW Autobox Mod 35

[PGAHOWELLS@domain.elided]

Hi all
Can anyone tell me how their revs change if lifting the foot at 70 in top.
If I am cruising at 70 or 3500 rpm, and I lift my foot of the pedal, the revs
drop to 3400. I can feel the car suddenly slow down. After 2 secs the revs
drop to 3250. (halfway between 30 and 35) 
Is this right? 
I have a strange idea my autobox is giving me engine braking in third, but
would appreciate some input for comparative purposes.
If so this could be the cause of my transmission overheating.
Peter H