Slipping Allison

[Moonie 58m]

I have a wonderful 2005, 2500HD with Duramax. Since around 16000 miles I had a small leak at the bell housing vent?

After the dealer pulled the tranny, replaced the seal, pulled the tranny and did something else, pulled the tranny and changed the bell housing, and pulled the tranny and replaced the torque converter, it stopped leaking, ATF anyway. I then had blue greas looking stuff oozing out for a while, which they said was assembly lube.

After that it seemed that it took a long time to shift, and I lost about 3 MPG. The mileage is terrible at cold startup, dropping to 11 - 13 on the DIC, but if reset after warm and driving country highwaym about 55 - 60 MPH with some stop and go, climbs back up to 19 - 21 usually. Of course dealer said there is nothing wrong, I should be happy with my 15 - 16 average, even though I was getting mid to high eighteens before. I sense that the converter is slipping. Also seems that it just isn't hooking up right when I go to pass. Engine revs up into the orange zone real nice, just doesn't seem to take off like it used to. Any good ideas?

[RCH]

Have replaced your external spin-on transmission filter lately? Also check that level is correct as too high or too low can cause problems. You can get the filter at an Allison dealer instead of GM, it is the exact same filter without the Generals mark-up. If you are not sure where an Allison dealer is near you, they have a dealer locator on their website(upper right corner).Good luck.