Transbrake

[spitzerscott]

What are some common causes of a "part time" transbrake?  TCI shorty glide in RED. 

[opa1]

What are the symptoms? Too low of rpm @ apply and or low pump pressure can cause a bunch of problems. Sticking modulator valve, bad solenoid, electrical? Band adjustment?

[bikeguy307]

If you are talking complete loss of transbrake it almost has to be valve and or solenoid related. If you have a release spring that fit in a pocket in the valve check it deformation. I have them fold over instead of going in the pocket keeping the valve from moving all the way in.

[spitzerscott]

It is not a complete loss,  He can't get it to work on the starting line, but if he stops on return road and tries it works. If we press the button in the garage we hear the solenoid click and we release we can hear it click again when the timer runs out.  At what RPM should he be at when he engages it?  First car we ever had with a transbrake so don't assume I know anything about it.    Transbrake 101 for dummies.

[spitzerscott]

Any Suggestions?

[wideopen231]

Biring rpm up as high as fell comfortable without having car move and try brake. If it works them more than likley pump is weak, You could install a pressure gauge and see what pressure you have at what rpm. Pull trans brake,valve(pay attention to direction) look at spring and see if slides freely in valvebody.

Check band adjustment and see if correctly set.


Check cable  for shifter to transmission lever to make sure its fully in low gear.Have seen one or two where its clicks in but lever is about half in half out.

[bikeguy307]

Ok so I locks the break while tried on the return road? Are you just pushing the button and it holds at idle or are you putting it at launch rpms? If it releases, or creeps/drives throught the transbrake when going up towards launch rpm then there is some sort of leak in the reverse circuit from the transbrake valve to the piston. This could be a worn valve, a blown gasket, or a bad seal on the piston. As wideopen said make sure the shifter is adjusted correctly. If you have a reverse pressure port in your case check pressure there and compare it to the low pressure port. If it is a total release of the brake while going up to launch rpm (the brake releases before the solenoid is de-engerized) suspect a weak solenoid. Keep us up on your findings.

[spitzerscott]

Thanks guys now I know more than I did. I have a guy coming over later that has knowledge about transbrakes  to try to show me some things, at least now I can ask some good questions.   By the way I did leave one small item out, this tranny set for 10 years before I started running it.  Could it just be sticky?  It looks like the solenoid just unscrews out of the case, is that true?

[bikeguy307]

Yes the solenoid unscrews. Sticking is a possibility but Im thinking it would go away after it cycles a few times.

Keep us posted, knowledge is power.

[spitzerscott]

Have not tried it yet but...……when we were playing with it, it had a voltage draw when other systems were turned on.  So the delay box was not getting full 12V.  Rewired and am looking forward to try it this weekend.   Stay Tuned!

[spitzerscott]

Well, back at track finally.  Transbrake still not working but, at least it something different.   When Joshen hit the button on the line the car backed up about 6 inches.  What may that add to an already ugly situation?               Thanks

[opa1]

Sounds like low pump pressure.

[msundstrom]

Had the same issue once, had some clutch material come off and restricted the filter, same as opa1 said low pump pressure.
Mark S

[bikeguy307]

Could be low pressure for sure. Remember the transbrake apply is a timing thing. When the solenoid moves the valve it sends low gear fluid pressure to reverse, so for a moment low pressure drops till reverse is applied, the key is have reverse apply and low "reapply" at the same time. So along with low pressure, a bad ring on the low servo, a band out of adjustment, and not enough clearence in reverse can all cause this problem. Check your pressure at the low servo cover and see what you have at idle.

[spitzerscott]

How much pressure am I looking for?  What size gauge?      Thanks