TH400 valve body for 1965-1990, OEM and ready to install. Ships fast from the USA.
Staging a TH400 against the converter - building RPM with the brake off and the car not moving - takes a transbrake, a circuit the stock valve body was never built with. This OEM 603206 kit adds that function to the TH400, 1965-1990, holding first and reverse together on command so you can load the engine and release into a clean launch, without changing the forward shift gate your current shifter already uses.
A stock TH400 valve body keeps first and reverse from ever applying at the same time, because there's no reason to in a street application - doing it on purpose is exactly what a transbrake circuit is for. This kit wires a dedicated solenoid into the valve body that holds both clutches together the instant you press a button on the shifter, locking the output shaft against the engine. Letting go of the button drops reverse and sends the car straight into first, which is how a transbrake delivers a cleaner, more repeatable launch than riding the brake pedal and foot-braking against the converter.
We also carry a reverse-pattern transbrake kit for the TH400 that changes the manual shift gate direction for a dedicated racing shifter. This 603206 kit adds the transbrake circuit on its own and keeps the standard forward shift pattern, which is the better fit if your shifter and linkage are already set up conventionally and all you want added is the staging function.
This kit covers the TH400 as used in 1965-1990 GM trucks, motorhomes, high-performance cars, and the Jaguar and Rolls-Royce applications that also ran this transmission, but a transbrake is a race-application part - match your case casting and confirm your shifter and wiring can support it before ordering, since this isn't a bolt-in behind a stock column shifter. The TH400 parts collection has the rest of what we carry, including the reverse-pattern transbrake kit if you need the shift gate changed too.
Wire the transbrake solenoid to its own dedicated button and keep it isolated from the reverse-light and neutral-safety circuits, then verify both the transbrake circuit pressure and normal drive pressure before making a pass. Our TH400 valve body testing guide covers how to read those pressures correctly. Refill with Dexron ATF, and pair this kit with a quick-spool valve system if you're also trying to bring the converter up to a higher stall speed on the brake, plus a floor shifter kit if your current shifter can't support a dedicated transbrake button.
| Transmission | TH400 |
| Year Range | 1965-1990 |
| Condition | Remanufactured / updated |
| Shipping | Ships from the USA |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It holds the TH400's output shaft by applying first and reverse together through a dedicated solenoid, so you can load the engine against the converter at the line without the car creeping, then release the button for an instant launch into first.
No. This kit keeps the standard forward shift pattern and only adds the transbrake circuit. We sell a separate reverse-pattern transbrake kit for racers who want the shift gate changed too.
No - a transbrake needs a dedicated button wired on its own circuit, separate from the reverse-light and neutral-safety wiring. A stock column or console shifter won't support it without modification.
Line pressure against the TH400's published range, since a weak pump or worn regulator gets worse under repeated staging, plus cooler capacity and the condition of the clutches behind the valve body.
Dexron ATF, and verify both transbrake circuit pressure and normal drive pressure before making a pass.
A shifter with a transbrake button if yours doesn't have one, a quick-spool valve system if you're also raising stall speed, and a dedicated cooler for the heat repeated staging builds.
