Hey guys, I need some help with this trans. FIrst off its a 99 4t40e. Probably for the past 6 months I guess its been, I believe this trans has been slipping. When it first started it was from 2nd to 3rd. Now its from 1st to 2nd and 2nd to 3rd is fine. The best way I can describe it is a hesitation from 1st to second. It just feels like a slip into 2nd instead of just being a regular firm shift. Manual shifting works fine. It seems to do it more after its warmed up in my opinion. But I believe it still does it even when its cold. We had the fluid and filter changed but did not have it flushed. My thoughts are among 3 things.
First that maybe because we didnt get it flushed that some of the old fluid still being in it means it doesnt grab the clutches like it should since that old fluid is shot. Also might explain why it doesnt do it all the time or as bad as other times. Second that maybe theres something wrong with the cooling system, perhaps the lines are clogged since it gets its coolant apparently from the antifreeze in the radiator and if the lines are clogged then of course the tranny would get hot and obviously make it start slipping. Third. I wonder if its the line pressure. Its only from 1st to 2nd. Oddly enough it shifts a lil better at WOT maybe because its forcing the shift alot harder. Anyway im just wondering whats goin on with it so any help would be appreciated.
Thanks

i have the exact same problem, if you find a solution let me know. Im leaning towards a cooling issue. Just because when mine is cold or its cold outside the transmission will shift fine, but the hotter the trans gets or the hotter it is outside, the more it slips and the sooner it starts slipping. Im gonna try an aftermarket transmission cooler.


2006 Black Cobalt SS Supercharged G85
13.91@102.77

Well at least im not the only one with the problem now we just need a solution. Ive also thought about gettin a cooler but id rather find out whats actually wrong with it and fix that instead of throwing stuff at it and hopin it will work. It probably wouldnt hurt to have a cooler anyway though. As far as I know the tranny has never been rebuilt or anything which means its got 105+ thousand miles on it so it may be time for a rebuild anyway but thats gonna be 1300 or so and I think thats for them to take it out of the car rebuild it and put it back and test it. Anyway thanks for the reply JaysonZ24, maybe we will get some answers soon.

yeah i also have the same problem i took mine to a well know tranny shop where i live and they told me its just becuase its getting old and that it should hurt anything just drive it nice which isnt going to happen and he hooked it up to the computer and it would read anything wrong while he test drove it. pretty much he is saying its just going to do that and its not worth the money to rebuild unless it goes out i just have a feeling somewhere out there someone knows the real anwswer and can help us all out and that was about 40k miles ago and my tranny is still the same hasnt gottn any worse so i have no clue but i hope someone does to help us all!!!!!

Yeah mine was taken to a trusted shop also and had the computer hooked to it and everything and he drove it and the comp didnt show anything and on top of that apparently it didnt slip when he drove it so he couldnt see anything wrong with it. I was told he even abused it a lil to see if it would slip and I guess it didnt and that really makes me mad because I can just take off normal and it takes 5 seconds or so before it slips into 2nd sometimes. But I agree though that I dont believe its actually gotten much worse even though it gets raced every now and then and I keep throwing parts at it to make it faster which should hurt a slipping tranny but it doesnt seem to that bad. I have no idea what to think of it. But I do know that its hesitation into 2nd hurt the times when it gets raced. I guess no one else knows that to make of it either. Thanks again for the replies guys.