Transmission Issue (Weird)

Ok I have a 98 Pontiac Grand Am GT 3.1 and automatic transmission.

It just started this weird problem and its not an everday problem. I'll put the car in drive and go on my merry way and as soon as i get on the highway and give it some gass, i guess the transmission acts like it cant shift up each gear and it keeps reving up studdering as it goes up each gear and it eventually gets up to the propery gear but its the weirdest thing. and then other times i get in and go and theres no problems...only now and then. anyone have any ideas what this could be...the transmission doesnt sound like its making any weird noises...seems to me like an electrical/vaccum problem on the tranny.. any thoughts of this would be great...im gonna bring it to my dads friend and put it on the scanner and see if any codes come up and then i'll repost.. thanks for any help.

Well your on the right track by having it checked for codes. When's the last time you had a trans fluid changed? There may be some dirt build up causing some problems. It also could very well be one of the vacuum lines or connection that's causing this and there is always a possibility that's it's not even tranny related, such as a bad computer, clogged catalytic converter, and so on... let us know if there any other symptoms that could help diagnos this better.

Hows the fluid level?

Had the fluid and filter serviced ever ?

Those would be a couple things to try, but I'm not a tranny guy :(
HEY TROY !

It chugs as it goes up each gear and the rpm is werid as it does it, its like its choking and sputters up each gear and it seems like it only does it when its cold. Because once its warm its fine or at least once the tranny fluid or whatever the case, once the car is warm. i can step on it and it shifts fine. The only thing is there are no service engine lights on at all. Everything on the car works in fine order. except this weird problem. Umm the fluid level is full and the tranny fluid is clean as a whistle. I was told it was done sometime in june. I bought the car on July 22nd. the car only has 82,000 miles. my grand prix's tranny finally took a shit after 170,000 miles :) that was a good car. I lvoe this car though and i hope it doesnt cost a fortune to fix.

I believe it may be whats called "morning sickness" .

Heres two threads where its discussed with possuble fix/cure :thumbsup:


http://www.automotiveforums.com/vbulletin/search.php?searchid=1686303
hope that helps !

Ok,

So today I took it out for a drive, had to go drop some mail off at the post office. It didnt do any hard studder shifting at all until 15 mins after I had the car started. So I'm assuming it must be electrically if it doesnt do it all the time. I went to Advance Auto and bought a nice little pocket scanner and nothing came up. Code Free. Maybe the scanner I got doesnt scan for trans codes..hmm but its a nice little 80 dollar scanner. I was reading previous post about it possibliy being the IAT sensor or a valve vaccum modulator? could these be any possiblity. If so where can I find these on the 3.1 engine? and what should I look for. Could it be a faulty fuse? Thank you all for the help i really appreciate it.

Most of the parts stores scanners dont read transmision DTC's.

The IAT is in the air intake tube, middle area on the back side facing the firewall.
Best bet is to take it to a trans shop that can scan/read the trans DTC's, some charge an arm and a leg, but some might do it for free.

I'll keep posting with the progress of what things pan out to be. Thanks for all the help xeroinfinity, its much appreciated. :)