Question: My 2007 Silverado Hybrid has been in the dealership numerous times due to serious jolts while driving (it feels like popping the clutch on a manual transmission). I thought it was a transmission problem, but my tech says it isn't, because when it happens, the computer says it's still in gear and not shifting. During all this, my torque converter went out and a prong on generator broke off. This time, it's been at the dealership for over a month. My tech is beside himself and GM is saying that this jerking is a normal function for the hybrid system. I personally think they're nuts! It's so bad that if anyone test drove it, I guarantee they wouldn't buy it! If this were a normal function of the hybrid system, there would be tons of complaints.
| 2007 Chevy Silverado front View
Answer: I haven't heard that type of complaint about a 2007 Silverado Hybrid. This isn't related to your problem, but some people have mentioned an electric motor whine while driving GM's new full-size hybrids. The revolutionary two-mode hybrid system utilizes two electric motors inside a rear-drive transmission. That means both motors are tucked in the chassis' center hump just a few feet from driver and passenger ear level. It's not excessively loud, but you do hear it. And if it's a $75,000 Escalade Hybrid, you really hear it. Alex Steele adds: In this case, I spoke directly with the owner of the Silverado Hybrid in question, which uses a somewhat primitive hybrid system compared with the two-mode system now offered by GM. This truck has a real problem, yet it's intermittent and hard to diagnose. The owner has been impressed with the dealership's courtesy and determination in getting it fixed, but there's been a lot of truck downtime involved already, and GM tech support suggesting it may be a normal condition hasn't helped. Damage to the drive motor/generator and torque converter, both located between the engine and transmission, has already been detected and repaired, but that hasn't fixed the problem. A stab in the dark is an alignment problem between the engine, bellhousing (which houses the hybrid drive motor/generator), and the transmission, possibly a broken or missing dowel pin, or even a crack in the bellhousing itself. Another suspect would be excessive crankshaft-end play causing the crankshaft, along with the drive motor/generator and torque converter, to walk back and forth. I'll stay in touch with the owner and update everybody on the outcome.
How To Reach AlexIf 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.
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