07 Silverado Classic Overdrive inconsistent?

07ClassicZ71 · February 11, 2016

New member here. I'm glad I stumbled upon this place.

I have a 2007 Silverado Classic 1500 Z71 5.3L with 109,000 miles in excellent condition. It's basically been under a carport it's entire life with regular maintenance and fluid checks. Transmission fluid is normal, smells fine but it hasn't been changed. Plugs and wires were replaced two months ago.

Recently it's been inconsistent in Overdrive as far as the RPMs are concerned. There's a slight bump shifting from 1 to 2 sometimes at take off.

On a GOOD day @ 60mph I'm between 1300-1400 RPM. I really don't even have to have my foot on the gas in my commute.

On a BAD day @ 60mph I'm at 1700-1800 RPM and in the gas a lot more. More difficulty on inclines and it will fall out if I don't keep my foot in check.

I drive about 65 Highway miles a day on a fluctuating road with flats, curves, and hills. It does not struggle if the OD is engaging properly. Lately though, I can take off and as I get up to speed I can tell Overdrive is not falling where it should be. I switch it into 3rd, then back into Drive so the Overdrive will engage again but it does not fall to the normal operating RPM range.

It was fine today, slightly warmer outside than other days.

It has had nothing replaced but an Alternator, Plugs/Wires, and a GM Valve Cover to fix the PCV orfice which was causing oil consumption.

Do you guys have any idea what is causing this?

07ClassicZ71 · February 24, 2016

Bump. Can this be transferred to the Drivetrain section? No help here.

txab · February 25, 2016

Have you had codes read? This is step #1

07ClassicZ71 · February 25, 2016

I'll get it hooked up as soon as I can and let you know if it shows anything.

07ClassicZ71 · February 26, 2016

Apparently the fuse was blown to the obd2 when I tried to get the codes. I didn't have a spare 15 so I'm picking that up at lunch today. It also appears my Oil Pressure Gauge sensor went out. It's stuck and registering at 80.