Boy I messed up!

Robbym Hope your getting some answers that will help. Here we like to have a lot of fun and also try your best to help a fellow Slingshot owner.

Too many unknowns.

Yep, you missed a shift...

Yep, grinding/whistling noise on decel...

Now whistling on decel... but no mention of grind.

What year model? How many miles on unit?

From where is noise emanating? Front, mid, rear of unit?

I am leaning in Funinthesun direction that you blew the shift pattern and tapped reverse.

Best shot in the dark is a belt drive deflection problem...

Did you hard shock the belt when you did find a gear?

Just not enough info to receive any real help.

Also no mention of any noise when using reverse. Does it feel and sound normal when backing up? (Don't forget there is a rev limiter that makes the engine sputter when over-accelerated.)

If it now sounds like things are operating OK and you'd rather wait until the end of the season before having the dealer check it out, I'd wait as long as the warranty is still valid. The engine and trans must be pulled from the front, so it's not something you want to do over. If not under warranty, I'd probably just look for a used transmission from as low mileage a Saturn Sky or Pontiac Solstice as I could find as that would probably be cheaper than trying to fix the trans, depending on local junk yard prices and local mechanic labor costs. As far as not having to pull the motor & trans again, make sure the hydraulics for the clutch are in perfect condition before putting everything together and back in the Slingshot!