second post tonight and i remembered another issue i'm having with my 2000 sunfire. at 70 mph, exactly 70 mph, there is a loud humming noise coming from the trans. not there at 69, not there at 71. it almost sounds as though it's trying to upshift, obviously it doesn't shift, it's in 4th lockup, to the best of my knowledge and there's no rpm change what-so-ever. i think it's coming from the planetary, what does everyone else think? thanks

No, think about it.

Planetlys, either hold, are held, or drive, and in third they do nothing, it is direct drive.

Lets say in 1st, they hold, in 2nd they are driven, and in 4th they drive. You wouldnt have a noise just in 4th and just at 70mph, if planetlys are bad they ALWAYS make noise in 1,2,4 and NOT in direct drive.

That is exactly how I diagnose tranmission issues, and it has never failed me yet.

The first thing I'do is whatever you RPM is at exactly 70, put the car in park and rev it to that and listen for the noise, I would first be 100% it is transmission and speed related, not engine RPM related.






- 2004 Cavalier - 124k, owned since new