05 Grand Prix GT shift bang into gear

[fredfree]

My 05 grand prix with 130k will bang into gear after stopping at a stop sign/light. It wont do it at every stop but when it happens, it is bad. The car will start to take off and then just bang into gear, and then will shift fine through all gears. I have noticed it usually happens after the car has been driven for a long period(45min or so). I have dropped the pan and changed the fluid (Dexron VI) and filter, and also installed the transgo shift kit(the springs in the accumulator). None of that really helped. The engien runs great, the tranny feels strong pulls hard no slipping. Was just wondering if it could be the EPC or TCC solenoid?

[torq455]

Sounds like it's slipping during the 1-2 shift. Pretty much means it's time for a rebuild. Does it kinda feel like it's going into neutral during the shift too, at least a little?

[fredfree]

Doesnt really feel as if it slips at all. It takes off nice and strong but when it makes the shift into second it bangs hard, and happens really quick. Is there anything else i could try or should try before heading down the rebuild road? thanks

[BillBoost37]

Two things are the most common causes of this in our transmissions. First is a bad input piston seal/worn piston sealing area. The other is a leak in a channel plate gasket.

What happens is fluid bleeds off, the pcm see's that the engagement hasn't happened and maxes out pressure which overcomes the bleed off. Bang, into gear you go.

[torq455]

I was thinking a broken 1-2 accumulator spring.

[fredfree]

Thanks for the replys. just wondering now if there is anyway to check either of those problems? how far would you have to disassemble the tranny to check either of those parts? can a scan tool be used to look at any of the shift data for possible cause? i have access to the gm tech2.

[BillBoost37]

The accumulator spring is a pan drop and few screws, very easy. I've never come across that issue, therefore didn't mention it, but yeah..if that's a possibility, easy to check.

[fredfree]

thanks guys, ill do some checking and see if i find anything.

[fredfree]

Just a quick update on this issue. i relpaced the pressure control solenoid about a month ago, and the problem hasnt acted up since, i have my fingers crossed for now.

[Rico]

That's strange. If the EPC solenoid was bad then it should have been banging into all gears. It should have set a code, P1860 I think. HMMMMM.

You can tell I've had this problem before.