95 Bonneville -
The transmission stalls to shift between 2 and 3. The engine will rev and after 5 to 10 seconds will 'slide' into the next gear.
We just purchased this car and will be changing the transmission fluid.
Could this be the vacuum mod? Or does anyone have a suggestion??

Is it supercharged, or not? L67 engine or L36?

I'm sorry to say a fluid change may only buy you a limited amount of time. That trans is on it'* last legs, and the second gear clutches are nearly done. Fluid may help for a short time, but it can't put clutch material back.

I'd be curious to see what your fluid on the dipstick looks and smells like after a short drive.

try some lucas trans fix, maybe that will help it last a lil bit longer.

That won't make up for lack of friction material on 2nd gear clutches. Save your money. You'll need it for the rebuild.

put some lucas in there but still didn't run right. just bought so we returned it. the car also had some electrical problems oh well. thanks anyway