[mnymaker]

Hey folks do any of you think that manually shifting your Seville Northstars from a stand still makes any difference in the acceleration or is it pretty much the same as standing on it while leaving it in drive and letting the computer do it?

Just wonder if letting it wind out more in 2nd gear and 3rd gear can help my SLS beat down other vehicles from a light or not.

Also is it bad for the transmission (manually shifting) I have a 1999 Seville SLS...

 

[jadcock]

If you put it in 2, you will increase the line pressure and will get a harder shift into 2nd gear. This does not hurt the transmission at all. Apparently, you can get the tires to chirp on the 1-2 shift by doing this, but I've never had that happen. The SLSes have a 3.11 final drive, and I think that soaks up some of the torque. The STSes are probably more apt to chirp the shift, with the 3.71 final drives.

I think the most agreed-upon method of drag racing is to put it in 2 at the light. Take off and after the 1-2 shift, slip it back up into D for the rest of the race. Any race on the street shouldn't need any more gear than 2nd though, or you're way out of legal speeds and endangering the rest of the motoring public. With an SLS, you can get close to 100 mph in 2nd gear -- that's way too fast for a city street.

 

[AKPsiMC03]

Manual shifting was mostly used on older autos which were controlled by either vacuum or a TV cable. THis was to extend the RPM range before the shift to maximize the powerband. In an electronicly controled tranny (like the northstar's tranny) it is not really needed because the computer sees that the pedal is at the floor and knows the driver wants to go allt he way to the redline.

I know in my old thunderbird if i floored it with it in D then it would go to about 500 RPM below the redline and then shift. When i would race i would manually shift it to bring it right to the redline or a few hunder RPM into the redline to the top of the power band.

In my ETC though, if i have the pedal to the floor, the computer brings it just to where it touches the redline then shifts. And at WOT, the shift is pretty damn firm. I like it.

 

[mnymaker]

Yeah I agree. I dont so much if any racing but just thought it would be good info to know anyway. Sometimes late at night when Im in the only thing on the street I like to see how fast I can get it to accelerate is all.

 

[jadcock]

Jay, try putting it in 2 for the 1-2 shift. You'll notice a difference. Even when I'm driving around town, I leave it in 2. The shift is really firm, even at 10% throttle. It feels like a very positive shift, at little throttle or at WOT. The line pressure IS increased with the selector in 2, so there is a mechanical difference in the tranny, even if it's electronically-controlled like our 4T80-Es are.

 

[Katshot]

It depends on the shift tables in the PCM flash program. On my car, the tables are identical in manual or auto. I've never seen a Northstar flash to know for sure but it is possible that the manual table is different from the auto.
If Jason has done it and says there is a difference, the table may have a different profile.

 

[jadcock]

I didn't know it'd be different in the PCM tables. If you put it in 3, the shifting is normal, I think (I'll have to verify that on the car after work). If you put it in 2, there's a definite change in shifting "force". The shift points don't appear to have changed...just the "positiveness" of the shift. It's much crisper.

 

[Katshot]

The shift tables on MY CAR anyway, has three basic modes:
1. Full Auto
2. Manual
3. Performance
The performance mode is not used on the B&D body cars as it is on the F&W bodies. So I only have auto and manual to play with. I can change shift points and firmness through the flash. I've had great success at the track with my "custom" tuning of the trans shift tables, and I'm only a novice at best. Experts like Ed Wright could work magic with them. Lord knows, I wish I could re-work the flash on my wife's Denali, I HATE the calibration they gave it.

 

[mnymaker]

Jadcock you are definately right about the firmer shift points in 2nd. I can tell a dramatic difference in shift firmness and torque when driving in 2 versus 3 or D. At least this is the case in my 99 Seville. Not sure what that body style is called, B, F, K??? Sorry not that knowledgable yet.

The car has great power when its running cool and driven in 2, and it can run a pretty high speed comfortably as it gets up the powerband before going to 3rd.

 

[jadcock]

The 92-97 Seville/Eldorado is built on the E/K platform. In 1998, the Seville moved to the G platform that the Aurora and previous Riviera are built on, which is very tight. The Eldorados continued on the E/K platform until their demise in 2002. My '97 Seville is an E/K car, and your '99 Seville is a G car.

 

[mnymaker]

Thanks for the info. I will try to burn that to memory