Truck feels like it is pulsating or shifting in and out of overdrive

MGANDY

MEMBER
CHEVROLET SUBURBAN

I have a 1999 Chevy Suburban 1500 5.7L 4WD, approximately 135,000 miles. Truck runs well and I keep up on routine maintenance issues. Did just have a new radiator installed because of a leak. My problem is when I'm driving the truck and it hits overdrive I can feel the truck pulsating or shifting in and out of overdrive. I can also watch the tachometer fluctuate just a little. All other gears shift fine and as I said everything else is running smoothly. Any recommendations? Thanks.

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good evening,

Shifting is controlled by the TPS or throttle position sensor. If it is out of adjustment this will happen.

Range (0-5 Volts):
The VCM uses the Throttle Position in order to determine the amount of throttle demanded by the operator of the vehicle. The TP sensor reads between 0.36-0.96 volts at idle to above 4.0 volts at Wide Open Throttle (WOT).

Another possibility is the torque converter itself. If the clutches are worn out in the converter it will also cause this.

https://www.2carpros.com/articles/automatic-transmission-problems

Lastly, it could be fluid. I would suggest changing the fluid and filter in the transmission.

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Roy

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