Why is your car moving backward when applying the transbrake in your powerglide?

Why is your car moving backward when applying the transbrake in your powerglide?

As a follow up to our previous blog posting, the other common problem with transbrake operation in powerglide transmissions is the transmission moving in reverse when the transbrake is activated.  Again, this can cause the car to roll out of the staging lights causing an instant loss.



Once again, we will review the normal transbrake operation:


  1. You activate the transbrake solenoid in low gear when staging.  The

    solenoid pushes the brake valve to a position in the valve body that

    redirects fluid.

  2. Fluid rushes within the transmission to apply the reverse clutch piston and reverse clutches.  This locks the transmission in a 1:1 fight between low gear and reverse.
  3. You increase engine RPM to prepare the car for launch.  The transbrake remains locked and keeps the car in place.
  4. You release the transbrake solenoid switch which removes fluid

    pressure from the reverse piston and clutches.  The car now has forward

    movement in low gear and accelerates down the track.


If the car is moving backward any during the transbrake setting and

staging process, it is likely due to one of the following problems:

 


  • Staging at an RPM that does not supply sufficient fluid volume

    OEM or weak pumps need additional RPMs to move fluid quickly and

    adequately to apply the reverse clutches.  Increasing your RPM before

    setting the transbrake is the first solution to try.

  • Low gear band not holding. 
    • The low gear band can be completely worn down which would prevent it from holding low gear
    • The band needs to be re-adjusted
    • The servo piston has failed, is leaking, or has broken a sealing ring
    • The band adjustment screw has broken or is bent

Check these areas if you are having transbrake trouble in your powerglide transmission.  These are simple fixes!  If you have any questions, contact our technical department @ 1-662-851-3213.

Posted by Brandon Barrentine at 4:11 PM