2004 Deville seems like transmission gear is slipping

It probably is! GM transmissions are known for failing. Time to move on to something newer! In my opinion it's not worth fixing! Hope that helps! Jim

I bought my Deville new in 2004. For years at times I could feel the transmission slip. Not bad but just noticeable. I thought about trading it but decided to keep it as it was not a constant problem. About 5 to 7 years ago it needed a new motor mount. I had it replaced and guess what? No more slipping of the transmission. My guess is that the mount was bad when it was manufactured or it was not secured right. Anyway, I am still driving it daily. However, the pan gaskets now need replacing so I intend to have that done. The repair place put green dye in the oil and used an ultra violet light to find where the leak was. Thank goodness it was’t a head gasket. Repair for that I understand runs around 2 grand. I have 150,000 miles on it and love the car. Believe it or not I live here in Michigan and after 19 winters it doesn’t have any rusted out doors or fenders unlike my 2004 Silverado that is almost completely rusted out beneth the doors.