2007 Chevrolet Avalanche 4WD 5.3L 4 speed (4L60E) ~140K miles. This is my son's truck. He bought it about two years ago from a certified Chevrolet used car dealership. It had a one year warranty. He lives in TN while I'm in VA. He called me tonight stating the transmission will barely shift into 2nd and he has to rev it high (3500 rpm) before it will shift into 3rd. It will not shift to 4th. No check engine light. Fluid level is correct. He also had a incident where half the gauges were not working. Shut off and restarted the truck and everything was fine. Don't know if that may be related or not? From my brief internet search, it appears the sprag gear (?) has failed. Does that sound right? Based on the symptoms he relayed to me it sounded more of an internal hardware failure and not electronic. I found a list of 30 common problems. 30 Common 4L60E Transmission Problems & Repair | Charlotte NC (at http://www.twincharlotte.com/transmission-repair-blog/bid/28391/30-Common-4L60E-Transmission-Problems-Repair-Charlotte-NC ) I'll point out the ones that may apply to his situation: 2. 1-2 shift does not happen at WOT (Wide Open Throttle) until you let off the gas: Best case: try replacing the TPS. Middle case: leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator). Double check by using the pressure gauge and watch for a big drop when the PCM commands 2nd gear. Worst case: poor line pressure rise (see below). 3. 1-2 Shift shudder at WOT (Wide Open Throttle); delayed or abnormal 1-2 shift; There's a problem ONLY on the 1-2 shift: 1-2 accumulator piston cracked or stuck cocked in the bore. Check the yellow spring inside the accum housing for breakage. Also, if the accumulator housing walls are scored, the housing must be replaced. 4. 1-2 shift is delayed and harsh, may not shift into OD: TPS needs to be checked for smooth and linear electrical response over the entire range of motion. If not, this must be replaced. 6. No 3rd or 4th gear: “3-4” clutches are worn out: Needs to be removed and rebuilt. The car is safe to drive (in 2) until you can get it fixed. 26. Shift suddenly become very hard. When going from park to either reverse or drive it slams into gear. 1-2 and 2-3 shifts are also harsh. All gears seems to work. Problem may be intermittent: Check TPS for smooth electrical response. If the response is jumpy or erratic at all, replace TPS (Throttle position sensor). Another link of 3 most common problems. The 3 Most Common Problems With The 4L60E Transmission (at http://etereman.com/blog/general-motors-transmission/the-top-3-most-common-problems-with-the-4l60e-transmission ) The first to second gear shift is late and harsh. This problem can be usually be traced back to the TPS (throttle position sensor) being defective. You will need a volt meter to test the TPS. With the ignition on, check the voltage on the TPS. It will vary as you move it. The voltage should increase or decrease in a smooth linear line. If it does not move smoothly you will need to replace the TPS. Refer to the shop manual for the correct voltage readings for your specific vehicle. Comments welcome.