Tranny seems to be slipping a bit

[kawboy8]

The other day I hooked my 6 x 9 enclosed trailer to haul a buddies Harley and everything seemed fine...except on some of the climbs I noticed the rpm's shooting up, but my speed didn't. I have an 07 F350 SD which normally doesnt even notice the trailer is back there...and it shouldnt. It doesnt do it all the time...but I am wondering why it did it at all. Could it be time for a fluid change? The truck has 89k on it. Any ideas? I am in Germany, so outside temp was cool, plus it was raining. The temp guages were all normal.

 

[95_stroker]

When you noticed the RPM's increasing was the tranny just downshifting or do you think it was slippage? I cant hardly imagine a 6x9 trailer that weighs what... less than 1000 lbs with a bike that weighs in under 700 lbs make your tranny slip.