I boughht a 87 GN last Sep with a freshly rebuilt trans. My question is pretty simple, since they shift back and forth at 40-45mph I usually drive in 3 unless I am getting onto the highway. Does this harm the transmission? I remember doing the same thing with my 350 IROC, never had any trouble- but a friend who is a Cadillac service advisor says leave it in OD at all times. advice?
You should always drive around town with the shifter in the OD. That is the only forward position where the valve body allows the torque converter to "freewheel" when you let off the gas.
I drive on "3" or "D" a lot. It won't hurt a thing. Uses a little more gas but a lot more fun to drive. No chuggle and less turbo lag.
Phil
I like driving in 3 also, if you put it into OD on a 40mph road the car just idles- this is the same reason you go to a higher gear in the diff, to keep the rev's higher. Scott may have the right answer, I was parking the car kind of on a hill, and it will roll backwards in 3 with no gas. I just wanted to make sure I wont fry the torque converter or something driving around in D. I only upshift into OD, I never downshift while the car is rolling. -thanks (I just put an external trans cooler on, keep new trans happy)
I'm going to have to go with Mr. Simpson on this one. I have been told by EVERYONE that I have asked, to keep the car in OD when not "racing". Why, I am not completely sure, but these guys know what they are talking about and I am not going to argue with'em.
I would also venture to say thet when you are not working the TC, it is not being worked. Less heat and wear occurs? So much for my degree.
Just a thought Jon. Are you sure it's the trans shifting back and forth from 3-4? Or is it the converter locking and unlocking. Try disconnecting the 3rd gear pressure switch from the connector at the drivers side of the pan. By doing this, the converter should only lock-up in fourth. I may be wrong. Like I said, just a thought.