at freeway speeds the tach is jumping 200 RPM's

2000 CHEVROLET BLAZER
160,000 MILES
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CALEBERICKSON
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I have a 2000 Chevy blazer and when I get to around 60-75 mph the rpms start to jump 200 rpm. Could this be a transmission problem? Happens at 60-75 mph
Dec 11, 2011 at 5:51 AM
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JACOBANDNICKOLAS
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Most likely not. If the check engine light has come on, have the computer scanned for trouble codes. A bad trans will slip at any speed. My guess is there may be a bad throttle position sensor or something like that.
Dec 11, 2011 at 5:55 AM
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CALEBERICKSON
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I have p1870 transmission component slipping code showing. Doesn't slip bad though. I was reading up and some were saying possibly torque converter acting up locking and unlocking. I was also thinking of a throttle position sensor going out
Dec 11, 2011 at 6:01 AM
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JACOBANDNICKOLAS
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200 RPM's would be hard to notice if it wasn't slipping. WHen the RPM's increase, do you feel the vehicle accellerate at all?
Dec 11, 2011 at 6:10 AM
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CALEBERICKSON
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Yes when it jumps up and down it will***** a bit. Gets very frustrating driving on highway
Dec 11, 2011 at 6:16 AM
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CALEBERICKSON
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Pull forward and back
Dec 11, 2011 at 6:25 AM
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JACOBANDNICKOLAS
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That leads me to believe the trans isn't the problem. Try having the computer scanned for trouble codes. Most parts stores will do it for free. I think it may be engine related. Also, check to make sure the trans fluid isn't burnt, low, or really dirty.
Dec 11, 2011 at 6:30 AM
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CALEBERICKSON
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Only codes present when scanned was the p1870. Transmission component slipping.
Dec 11, 2011 at 6:33 AM
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JACOBANDNICKOLAS
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IS the trans fluid clean and full?
Dec 11, 2011 at 6:45 AM
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CALEBERICKSON
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I need to check the fluid. Possibly low. I also have a bad thermostat that im going to fix would that have anything to do with the lurching? Being that the engine is not getting to normal operating temp?
Dec 11, 2011 at 6:53 AM
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JACOBANDNICKOLAS
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No to the temp, but yes to the low ATF.
Dec 11, 2011 at 7:03 AM
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CALEBERICKSON
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Ok thanks. So possibly could be due to low tranny fluid and slipping at higher speeds
Dec 11, 2011 at 7:09 AM
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JACOBANDNICKOLAS
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Yes, low fluid can lead to low fluid pressure allowing the clutch pack to not be locked.
Dec 11, 2011 at 7:30 AM