Strange goings-on with my transmission

[ZigZag03]

I just bought a very nice little 2008 explorer limited v8 with 89k. my issue is with (i think) the auto transmission, which works fine except when in overdrive between about 40 and 50 mph. you could almost call it an engine miss, except that otherwise the engine runs beautifully at all speeds and rpm ranges in all lower gears. but, when at that speed range, it surges, shudders, misses, i can't come up with the right word. to me it is like it can't decide which gear it wants to be in, although there is no reflection of this in the tach. maybe the converter locking and unlocking? i don't know exactly how to describe it. it doesn't seem to do it at highway speeds, say above 55. i don't have any service records, don't know when the tranny was last serviced, if ever. and clearly thats probably the place to start. anyway, anyone with thoughts on the matter i'd be grateful to hear from, and thanks.

 

[ZigZag03]

would like to update this to say that indeed i DO see some variation in the tach, a couple hundred rpm. get up past 50 or hang below 40 and it seems pretty happy. drove it cold this morning and had the issue (cold being high 40s, its florida, and that's cold!) then 40 mins later drove it again and it was fine at all speeds. hmmmmmm