c6 grinding going into Park

[redstone65]

This is the first real test of this transmission. We have zero knowledge of what shape it's in. The driveshaft is currently out of the truck.

When I start the engine and the selector is in Park, the output shaft spins. If I change the selector to Reverse, the output shaft stops and starts spinning the other way. In Neutral, and every other gear, the shaft spins. When I return the selector to Reverse, it starts spinning the other way. But, then when trying to get it to go back into Park, it grinds and won't go back.

My guesses are:

- Torque converter bad, or not seated correctly?
- Selector index position is wrong inside the trans?
- Reverse band too tight?

Any ideas?

I have another C6 here that is also of unknown quality so I don't want to do a swap until I have a little more to go on.

[cep62]

Put your driveshaft back in .
It'll keep it from spinning so you can put it in park.

[CH3NO2]

The rear yoke cannot be moving when you try to put it in park. That's where the parking pawl is.

[redstone65]

Ah. Thanks guys. Will do.

[redstone65]

Worked like a charm. Thanks guys.

I get why it was grinding going back into park, but I still don’t understand why it was spinning in Park initially. Wouldn’t the pawl lock the output shaft?

The only trans rebuild I’ve done is a 4r70w. I know nothing about the c6 internally.