Dex VI in a 4L60E?

The newer ones will effectively replace the older ones but in this case compatibility is poor so you really do need to flush out all the old fluid and replace it all, you can't just mix the two.

I am not a fan of doing a full flush unless it's being done on a regular basis, because the flush can dislodge junk and suddenly you start having problems that you weren't having before. If it's an older transmission that hasn't been getting fluid changes or flushes on a regular schedule in the past, I would much rather do a change than a flush.

So... if you do a change, you will need to use Dexron III. If you do a flush, the Dexron VI will be a more stable product.

Your call. It's your transmission and you know the history and we don't.

--scott

The VI is a thinner fluid even though it is the current recommended. That may affect shift timing. If the trans has high mileage already, and it shifts ok, it might be best to keep it on III. See the other reply, valid points made.

____ Xeno