I am at a lose on getting my car to shift right...????

Mr Jones 4.6 · Aug 16, 2008

I have a 1998 Mustang GT which has a built motor and a custom dyno tune. I also have 4.10 gears installed and I am experiencing some problems. I have been playing around with the software and was wondering if anyone could tell me what all settings need to be changed to correct the computer for the different gears?

Curently as the car drives it locks into overdrive at 35mph but I know it should lock up at 45mph. I do have a speedcal installed to correct the speedometer but it did not help the shift points or downshifts.

Right now the car at WOT shifts from 1st to 2nd at 5,000 rpms and then 2nd to 3rd at 6200 but the rev limiter kicks in for some reason. I have tried to manually shift the car but once it goes past the specific rpm it activates the rev limiter.

Now one thing I have not touched is the MPH shift points

All I'm looking for is for someone to tell me what exactly I need change in the tune to make the car shift where I want it to. I would appreciate it greatly.

Thanks

95-stang · Aug 16, 2008

"I do have a speedcal installed to correct the speedometer but it did not help the shift points or downshifts".

Nor mine, but unless i get one of those Baumann things to alter the shift points i'm stuck, btw i have 3:73 gears.
Do you find yours "chugs" a bit, or is it just mine. I have to drive without O\D until i'm past 40mph, whereas before i could leave it on permanently.

Mr Jones 4.6 · Aug 16, 2008

Ya my car locks into overdrive at what it thinks is 45mph but its actually 35mph. Theres got to be more in the tune though, or else other people would have this problem.

nyuk98gt · Aug 17, 2008

Mr. Jones 4.6:

What software are you using? If it is SCT's Advantage (Pro Racer Package stuff), I may be able to help. In fact, better help than me is available in the Pro Racer forum at sctflash.com. You need to contact SCT and tell them your Pro Racer number and they will grant access to the forum.

Here are some things to consider:

J-mod: This will make the shifts quicker. Quicker shifts are required because the rate of increase of RPM is much higher with 4.10's than with 3.08's. Jerry W. explained this issue very clearly in his "Transmissions 101" articles (available at TCCoA.com in the Tech Articles/Transmissions section). Basically, the time to go from, say, 3000 to 4000 RPM, is LESS with 4.10's so the RPM-based shift points have to be set LOWER with higher numerical gears. I recommend (very strongly) that the J-mod is done to any car that has higher numeric rear gears.

The transmission will shift on either MPH or RPM trigger points depending on how things are set up in the shift schedules. If you have PRP, you can change the MPH and the RPM points to what you want.

The N/V (RPM to vehicle speed) has changed and the PCM may not be able to accomodate a big change from 3.08 to 4.10. The MPH shift points should be "ratio-ed" for the new gears. You can also change the 'base N/V' in the tune to get things closer.

Is your SpeedCal set so that your speedo/odo are accurate? If not, get it dialed in so there is minimal error. If the signal is inaccurate, it affects transmission operation.

Chris