Ecotec Sunfire transmission

LIL_VINN

MEMBER
2005 PONTIAC SUNFIRE
4 CYL
FWD
AUTOMATIC

I have a 2005 Pontiac Sunfire with a 4 speed automatic transmission and a 2.2l ecotec. The car is used for 1/3 mile dirt track racing. I'm having a very big problem I burnt up a tranny at the beginning of the season and changed it. Now the car runs fine during the heat races and shifts fine (i put the tranny in second gear while racing not in drive) however when I race the feature after about 10 laps the car stops shifting it feels as though the car is slipping. But if you let the car cool off and start it later it will shift just fine. One other thing is that the speedometer goes off when this happens. I've tried a new computer and also unplugging the gauge cluster I don't know what to do anymore.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Replace the vehicle speed sensor. That is most likely what is causing the speedo problem and the shifting problem.

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Monday, September 5th, 2011 AT 3:07 AM

LIL_VINN

MEMBER
3 POSTS

The speed sensor that's located on the backside of the tranny? That has the 2 wire plug in? Or are you talking about the throttle positioning sensor, I replaced the whole throttle body so it has a new throttle positioning sensor. I really can't figure it out honestly last night I was racing 15 laps I had the lead there was a caution I so we slow down I get back on the gas and it feels like its slipping then I bump it up into 3rd and it goes a little but just hits the rev limiter and I ended up not finishing lost 650 bucks because of it.