Transbrake issue

Bob Don · 07-31-2023, 09:05 AM

I have a 92 Mustang, 302 FI C4 (reverse valve body w/air shifter) in SS. Had trans rebuilt over the winter. Ever since, transbrake isn't working correctly. Voltage was checked, solenoid works, transfluid pressure was checked. First run of the day everything works fine but on subsequent runs, transbrake doesn't hold and I go through the lights. Happened yesterday again at LVD. Anyone ever have this happen? Valve body issue? Thanks for replies.

Keith 944 · 07-31-2023, 04:00 PM

I had a hipster solenoid roll pin, started backing out, and sometimes it would catch not engage, engage or get stuck. Not sure if your trans brake even has a roll pin in the solenoid but definitely something to check.

GTX JOHN · 07-31-2023, 10:43 PM

In my SS car I had a similia issue.
Turned out that I had a leg strength issue.
I am 75.
I had to lower the pressure switch a lot to
compensate.

Tom Goldman · 07-31-2023, 10:52 PM

Quote:

Originally Posted by Bob Don

I have a 92 Mustang, 302 FI C4 (reverse valve body w/air shifter) in SS. Had trans rebuilt over the winter. Ever since, transbrake isn't working correctly. Voltage was checked, solenoid works, transfluid pressure was checked. Firs run of the day everything works fine but on subsequent runs, transbrake doesn't hold and I go through the lights. Happened yesterday again at LVD. Anyone ever have this happen? Valve body issue? Thanks for replies.

Bob it sounds like you have a rear band servo seal that is leaking .It probably works on the first hit because the fluid viscosity has not thinned out yet. how does reverse feel once the fluid is warmed up after the first run?

Bobby Fazio · 08-01-2023, 04:06 PM

Whose valve body, internal or external trans brake selenoid and does the trans work fine when not using the trans brake? Can you hold it with the foot brake?

tstickff · 08-01-2023, 10:00 PM

Also make sure your air bottle has enough C02, might have enough pressure in the bottle first time out but loses air pressure? Maybe an air leak? Consider switching to an electric shift instead of air shift, I did and much happier.

Tim Stickles

nickh · 08-01-2023, 10:02 PM

Quote:

Originally Posted by GTX JOHN

In my SS car I had a similia issue.
Turned out that I had a leg strength issue.
I am 75.
I had to lower the pressure switch a lot to
compensate.

John we ain't old we are just "seasoned"!

Eman · 08-02-2023, 11:44 AM

Go through the lights, I'm guessing you go forward when on the TB. Does it hold at all or does it roll forward as soon as you take your foot off of the brake? I'd check the wiring first to make sure the hot solenoid isn't showing a fault in the wiring. 2 wire solenoid? Where is it grounded?

07-31-2023, 09:05 AM	#1
Bob Don VIP Member Join Date: Oct 2002 Location: Greater Boston Posts: 1,491 Likes: 1,081 Liked 882 Times in 188 Posts	Transbrake issue I have a 92 Mustang, 302 FI C4 (reverse valve body w/air shifter) in SS. Had trans rebuilt over the winter. Ever since, transbrake isn't working correctly. Voltage was checked, solenoid works, transfluid pressure was checked. First run of the day everything works fine but on subsequent runs, transbrake doesn't hold and I go through the lights. Happened yesterday again at LVD. Anyone ever have this happen? Valve body issue? Thanks for replies. __________________ Bob Don 128 SS Last edited by Bob Don; 08-01-2023 at 08:16 AM.

07-31-2023, 04:00 PM	#2
Keith 944 VIP Member Join Date: Feb 2006 Location: Dela-where? Posts: 2,184 Likes: 1,143 Liked 1,854 Times in 573 Posts	Re: Transbrake issue I had a hipster solenoid roll pin, started backing out, and sometimes it would catch not engage, engage or get stuck. Not sure if your trans brake even has a roll pin in the solenoid but definitely something to check. __________________ KEITH MAYERS 2-1/2 X somebody Still many X nobody

07-31-2023, 10:43 PM	#3
GTX JOHN VIP Member Join Date: Jun 2009 Location: Boulder City, Nevada 89005 Posts: 2,709 Likes: 2,737 Liked 2,400 Times in 680 Posts	Re: Transbrake issue In my SS car I had a similia issue. Turned out that I had a leg strength issue. I am 75. I had to lower the pressure switch a lot to compensate. __________________ John Irving 741 Stock 741 Super Stock Last edited by GTX JOHN; 08-01-2023 at 09:31 PM.

08-01-2023, 04:06 PM	#5
Bobby Fazio VIP Member Join Date: Nov 2009 Location: Egg Harbor Township, NJ Posts: 1,464 Likes: 1,417 Liked 4,355 Times in 498 Posts	Re: Transbrake issue Whose valve body, internal or external trans brake selenoid and does the trans work fine when not using the trans brake? Can you hold it with the foot brake? __________________ '65 Mustang SS/L & L/SA DriverInterviews.com \| App.DragInsights.com

08-01-2023, 10:00 PM	#6
tstickff Member Join Date: Mar 2009 Posts: 463 Likes: 308 Liked 542 Times in 135 Posts	Re: Transbrake issue Also make sure your air bottle has enough C02, might have enough pressure in the bottle first time out but loses air pressure? Maybe an air leak? Consider switching to an electric shift instead of air shift, I did and much happier. Tim Stickles __________________ Tim Stickles

08-02-2023, 11:44 AM	#8
Eman Member Join Date: May 2014 Location: E TN Posts: 463 Likes: 16 Liked 125 Times in 71 Posts	Re: Transbrake issue Go through the lights, I'm guessing you go forward when on the TB. Does it hold at all or does it roll forward as soon as you take your foot off of the brake? I'd check the wiring first to make sure the hot solenoid isn't showing a fault in the wiring. 2 wire solenoid? Where is it grounded?