Your Gen Slide should certainly not go so fast as to be alarming. Mine was agonizingly slow.
First off we need to know the year and model of your TS.
Without knowing that I'm gonna guess at a couple of things.
Your generator slide probably runs on pneumatics, so you don't need the engine running, just air in the tanks.
I think up on the firewall is an adjustment to meter the air to the slide cylinders and that should allow you to set the rate of in/out.
I am pretty sure someone else on this forum will chime in with more detailed and correct info.
Best place to put your year and model is in your signature.
In addition put aside about an hour a day and cruise through EVERY THREAD on this forum. Many you can skip from their title but doing this will;
1 tell you a lot about your TS and how to properly operate it.
2 answer many questions you already have
3 Hopefully keep you from calling and paying a repair guy to show you how to turn something on that you thought was broken.