I recently changed my tranmission oil and filter. Beforehand the transmission seemed ok but after it seems like the brake is on. It runs fine but it did drop 2 mpg 18 vs 20. I am wondering if it is just the new fluid or perhaps there is a leak at the little seal where the tranmisioon filter goes. I did not replace the seal, just pulled the old filter old and popped a new on in. Should i go back in a replace it. Do i reall y have anything to worry about? Thanks for another view.

 

I always recommend replacing the seal when the filter is replaced but I doubt that's your fuel milage problem.
If you've dropped 2 mpg perhaps it's due to the weather, it's colder now and the engine will run rich longer til it has time to warm up.

 

I didn't replace the seal because actually i didn't realize that there was one in there. The drag effect seems more like the transmission is just tighter feeling, although there was a noise on accetaration that i thought was valve noise that has gone away with the fluid change. Perhaps the tranmission is sounding like it should be. I have about 222,000 miles on the truck now while i put on about 110,000 of those my self. This was the first ti,me it was changed since i got it.