Just when I got all the ticky-tack **** all ironed-out and a valid inspection sticker earned after rebuilding the whole EVAC system front-to-back, ... my Monte is harsh-shifting, slipping and acting-up something fierce.

PO1811

What should an old-timer do when it's "Tranny Time?"

 

A short term fix would be Lucas Oil Trans fluid.
I know of people who have held off the replacement by using this stuff. Follow Directions on the bottle.

 

Can you rebuild one yourself?

Best of luck!

 

Check this out: p1811 or p01811 on 03 grand prix se 144,000mi 4t65e transmission

 

Have you looked into the solenoids, TCC and EPC in the side cover of the transmission like a previous person suggested. Its not the easiest thing but it really isnt bad.

The monte carlo 4t65e and 4t60e transmissions are notorious for these things going bad. especially if you are not changing the fluid as you should. They sell kits of the ac delco sensors on ebay for around 100 bucks.

I recently had this issue (hard shifting in each gear) and replacing these fixed the issue. The big things of this job is taking out the driver side steering knuckle, and dropping the subframe a foot, which really isnt all that bad. you may want to do your fluid filter if you end up doing this. also torque wrenches are a must