Do you have a Cottman or Ammco trans shop by you.
They will do a free trans check up (at least that is what they havebeen saying)

 

$2500!? Whoa... I would have another opinion, Like mrrench said take it to aamco. Heck even a tuffys they do free checks.

 

I blew up a tranny in my '01. Reverse gear. Cost me $1,400. They are a real problem. I run into a cabby in Toronto with an Impala, on his SIXTH transmission, 250,000mi. I'm hoping my 4T65E-HD holds up better, but most of the parts are the same as a 4T65E. I just had the flexplate and torque converter replaced. Broke the flexplate. I'm not the only one, either, as there was a service bulletin on it.
Catalyc convertors are a real problem, also, as they won't give a check engine code, but they always have a loss of power with them. That's the sure sign of a bad cat', as loosing power going up-hill.

http://www.cardomain.com/ride/2319272

 

I'm the one who had the bad cat. I took it to AAMCO they looked at the tranny, Oh my, it needs a new one. Put a new one in, it still had the problem. Well we now think it's the fuel pump, we'll put a new one it at no labor charge. I pick it up after they say they're done with it, put 5 miles on it and drive it straight back. It's still not running right. They drive it accross the street to a Pontiac dealer and he drills two holes on either side of the cat to check the flow. It was the cat being clogged up not letting it shift correctly. To much back pressure. $200 more dollars over what I just spent, I'll keep that figure to myself, and the car drives fine.

Start with the smallest problem and work your way up.

Right now I've got a new Tranny, Plugs and Wires, Fuel pump and filter, and the only problem was the cat. converter. I dropped way to much money on a 7 year old car with 130K miles.

 

P1811=long shift time. That to me indicates that as long as your trans' fluid isn't all burnt up, you have a bad cat'. Secondly, a tranny rebuild shouldn't cost over $1,400 on the high side, $1,100 low side. US$. Any thing more is a rape job. So that's probably close.
MAKE SURE YOU HAVE ALL AFTERMARKET PARTS, INCLUDING A HARDENED HUB, NOT THE CAST PIECE FROM THE FACTORY!
I have had a bad solenoid once, tho. That doesn't require a complete rebuild. Sounds like they didn't replace the solenoids when they rebuilt it if that is the problem.
I run into a cabby in Toronto with an Impala on his SIXTH tranny!

http://www.cardomain.com/ride/2319272

 

First check the cat converter as it does a ton of weird backpressure issues.

I would alsosuggest to forget the rebuild and just get a race transmission and be done with it. It will have better parts and as long as you don't beat on it the tranny should be good for a long time due to hardend parts.

Another good idea would be to get a used 4T65E-HD from a 2000+ Grand Prix or 2004-2005 Monte (previous to 2004 the HD was only available in the GP's.) You should have to worry about these going out either as they are built pretty strong.