More boost equals higher shift point?

[Ed Valvo]

The more power I make via turning up the boost, the higher my shift points go. Is this normal? Or maybe the added power is making the motor rev so quickly that the tranny doesn't shift in time? It's not by much, just a few hundred RPM difference.

 

[Lee Thompson]

boost

IMO, Yes. My car also shifts at a higher rpm, 1-200.
This same ? was asked a few months back and one of the trans guys on here said NO, But I have found this to be the case on my car and others.

 

[chris718]

the driveshaft rpm dictates at what mph it will shift.with an increase in input torque the convertor coupling can change slightly and allow a higher engine rpm to be reached at the same mph that the transmission shifted before adding boost.your numbers sound correct.

 

[Ed Valvo]

Thanks guys. So I'm not the only one. So when adjusting shift points, I will leave it on the low side since it will rise when I bury the boost gauge.

 

[chris718]

REMEMBER THAT I SAID THE GEAR CHANGES WILL STILL HAPPEN AT THE SAME DRIVE SHAFT RPM/ MPHOUR.NOT ENGINE RPM.

 

[c&cgn]

Mine went up as well. On the street with pump gas etc, monitoring on Directscan the car will shift @ 5150 pretty much every time. The only time I have been to the track with the new motor and some good boost it was shifting around 54-5500. I have no problem with this since it makes better use of my cam but I'm not sure if it will always be that way or what? If I get the boost higher than the 23psi I was running will the shift point continue to rise?

 

[WE4]

And another consideration is heat.

The converter builds more heat with more torque created from more boost so fluid thins a tad changing viscosity a touch making the shift valves and PR valves a little later isn moving as govenor will blow off later also.
So yes, it can in effect have a slight one. Now if it were thousands of RPM, that might be something to look at...

Bruce
WE4
PTS XTREME

 

[chris718]

ACCORDING TO EVERY VEHICLE WE TEST WITH A 2004R THE OIL PRESSURE IS RIGHT AROUND 235 COLD AND 200 HOT IN PNODAND D AT FULL TV.THIS SHOWS THAT THINNING OUT OF THE OIL CAUSES AN INCREASE IN INHERENT CROSSLEAKS IN THE TRANSMISSION AND A RESULTANT PRESSURE DROP.I WOULD HAVE TO SAY THAT AN INCREASE IN TEMPERATURE COULD EITHER RAISE OR LOWER SHIFT RPM SLIGHTLY DEPENDING ON WHICH POINT IT IS BLED OFF AT AN INCREASED RATE.IN THE TV UPSHIFT CIRCUIT IT WOULD CAUSE EARLIER SHIFTS AND IN THE GOVERNOR UPSHIFT CIRCUIT IT WOULD CAUSE A DELAY OR SLIGHTLY LATER SHIFTS.

 

[ulose2av6]

REMEMBER TO USE RED CLUTCHES.NOT THOSE BLUES