Troubleshooting 4L60E transmissions
 Basic details on troubleshooting the 4L60E transmission
It takes some working knowledge of the electronically controlled transmission to determine if the problem is engine, transmission or chassis related. Some general questions to be answered are:
- Does the speedometer function correctly?
- Does the in dash shifter indicator function correctly?
- Is the check engine light on?
- Has the system been scanned for codes and code history?
 4L60 - TH700R4 - 4L60E drivability problems
Has the transmission lost reverse? Has it also lost 2nd gear and 4th gear (overdrive)?
If those are the problems, suspect that the drive shell has broken or has stripped out splines. When the drive shell fails, the results is no reverse, 2nd gear or 4th gear. Check for there being three complete shifts of the forward gears. Shift 1st to 2nd gear, then shift 2nd to 3rd gear, then shift 3rd to 4th gear (overdrive).
A good quality scanner that can read codes, clear codes, and can read a live data stream as the transmission is controlled by the PCM is needed, not just a code reader device.
Some scanners can take over control of the transmission for a better diagnostic test of the operation as the vehicle is driven.