99 STS won't shift at redline at WOT - Page 2

Jad2 · #16 (**permalink**) 05-21-08, 05:28 PM

Well, I think I've KINDA figured this out. I don't think there's anything wrong, anymore...but I still can't explain the change.

I was looking at the tach today and realised it used to shift at 6250, actually, not 6500. I thought about what BBob said and decided not to worry about the red area on the tach and to just let the computer worry about protecting the engine. So I did a WOT and sure enough, at 6700/6800 or so it shifted without any drama. Did it again and same thing. So, I think it's actually shifting at around 6500 now but I'm just seeing the needle swing past like BBoz described. With no codes and a proper shift (no fuel cut out, so it can't be hitting the rev limiter at 6800), I think it's fine. The only thing I can think of is that the ECM was reset when the engine/trans was out and is now shifting how it should...maybe before someone really babied it and it lowered the shift point for WOT? Who knows.

97EldoCoupe (member on this board) did all the work (and did an excellent job, along with helping me track down this issue) suggested that maybe the over-torqued main bearing bolts restricted the engine before and now that he has retorqued them to the FSM specs, the engine is turning more freely. Hard to say.

But I think it's case closed on this issue, I'm not going to worry about it. If anyone needs Caddy work done, even if you are located a ways from Ontario, I'd recommend you talk to 97EldoCoupe (Jake)...he's honest and very reasonable and knows these cars.

Thanks everyone for your input on this, especially sub (appreciated your RPM numbers, mine match yours FYI).

submariner409 · #17 (**permalink**) 05-21-08, 05:50 PM

Jad2......Thanks for the comeback. Drive it like you stole it !!!

Darien......Outer tire diameter will not materially affect shift rpm points (except when torque sensing comes into play): what the rolling distance difference does is to throw the speedo and mileage calculations off by some + or -percentage, depending on whether the installed tire rolls further or less in one revolution than the oem calibration.

Think of tire differences this way: A John Deere tractor rear tire rolls one heck of a lot further in one revolution than a lawn mower tire does in one revolution. A bit extreme, but the analogy holds until all 4 tires match the design outer diameter.