How to Tell When the Sprag in a Torque Converter Is Going Bad
by Francis Walsh
Ask anyone who has had a broken-down car or truck due to “something inside the transmission,” and they might tell you that before a transmission technician told them what was wrong, they had no clue. You should know that saving money on an expensive transmission job could be as easy as knowing how to tell when the sprag in a torque converter is going bad. Learn what to expect and fix it fast if and when you have a problem with a bad sprag in the torque converter.
Step 1
Enter the vehicle and engage the ignition using the key. Roll down the window and use your ears to listen to the sounds that are coming up from the transmission. Upon an initial period of one to two minutes of warming up, you can begin to test-drive the vehicle to tell when the sprag in a torque converter is going bad.
Step 2
Shift the vehicle in drive to pull forward. Does it engage the gear and move forward when in drive? Normally, if the forward sprag in a torque converter is going bad or is broken, it will not allow the vehicle to move forward when in drive.
Step 3
Place the vehicle in park again and then move the shifter into the reverse position. Does the vehicle go in reverse? Even if a torque converter sprag is going bad, it will still allow the vehicle to be placed in reverse and have movement.
Step 4
Check the other remaining gears in the same manner. Place the shifter into each of the manual shifting points and attempt to move forward. All this can be done within a small area. From a standing position you can check to see if all the gears will engage properly.
Step 5
Operate the vehicle normally, driving within a one mile radius from your starting point in case a broken or bad sprag stops the transmission from working properly. During the drive, you can shift through the forward gears. Check again for the “missing gears” which will be the drive and first gears when the sprag in a torque converter is going bad.
Step 6
Complete the test drive by returning to the location of origin and analyze the results. Did the transmission shift easily through all the gears? Then it probably is not the front sprag in a torque converter. It’s when there are “missing gears” that you can consider having the torque converter removed and checked before having to pay for a new transmission rebuild.
References
Tips
- Check the transmission fluid level and be sure that isn’t your problem first. Try to shift in and out of the missing gear when taking the one mile test drive to see if the sprag will engage or not. A broken sprag will not let the gear engage at all. Always determine if the problem lies with the torque converter BEFORE any transmission rebuild.
Things You'll Need
- Car or truck (GM/GMC)
- Automatic transmission
- Roadway (one mile)
Warnings
- During the test drive, do not drive in excess of speed or maneuvers. A broken sprag can result in catastrophic damage that can create a “locked” transmission which is dangerous when driving at any speed. Always attempt to diagnose a problem “off the street” first.
Writer Bio
Francis Walsh has been working as a freelance writer since 2003. He has contributed to websites such as Shave, Autogeek and Torque & Chromeas, as well as provided content for private clients. Walsh has worked as a performance part-packer and classic car show promoter, now serving as crew chief for Nitrousfitz Racing.
