Question: I have a 2000 GMC Sierra that won't give me second gear. Sometimes it will shift, but regularly it stays in first. Any suggestions?

Answer: Without knowing whether your truck is a half-, 3/4-, or one-ton, or what engine and transmission it has, I can't accurately search for relevant technical service bulletins that may help. So, we'll just go over the basics. We do know that it's an electronically controlled transmission. And one of the most important phases of diagnosis is determining if the problem is electrical or mechanical. With that said, check the transmission fluid level and condition. A lack of fluid can lead to finding a significant leak, and burnt/black fluid may point to a transmission that's toast.

Did the malfunction indicator lamp come on? Even if it didn't, we have to scan the system for diagnostic trouble codes. It's ridiculous not to. There may be a transmission code pointing to a circuit or part failure of the 1-2 shift solenoid. This is the component that receives a command from the powertrain control module when it's time to shift from first gear to second. But again, it may be an internal mechanical failure such as a stuck hydraulic valve or perhaps a clutch drum -- which is needed to engage second gear -- not being fully applied. There are even trouble codes that tell if the problem is definitely mechanical and cannot be produced by an electrical failure.

This is not something to attempt yourself. Get it to a GMC service department or qualified transmission shop. They'll start with a road test, followed by checking the fluid and trouble codes, and then pressure-testing the unit, if need be.

This is not something to attempt yourself. Get it to a GMC service department or qualified transmission shop. They'll start with a road test, followed by checking the fluid and trouble codes, and then pressure-testing the unit, if need be.


How To Reach Alex
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.

Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage -- visit Alex Steele at www.RealWorldAutomotive.com.