TH400 Valve Body 1972-1974, used and ready to install. Fits the TH400. Ships fast from the USA.
If your 1972-1974 GM truck, motorhome or full-size car with the TH400 is shifting harsh, running away in high gear, leaking at the modulator, or burning converters and clutches from pressure that will not settle down, the valve body is where that chases back to. This is a used, tested TH400 valve body built for the early-1970s casting, so you install a known-good hydraulic section instead of guessing at a worn pressure regulator bore.
The TH400 is a fully hydraulic 3-speed with no onboard computer, so the valve body alone is the hydraulic brain of the unit: a vacuum modulator and governor feed it signals for engine load and road speed, and the valve body's spool valves and bores turn those signals into line pressure, shift timing and clutch apply. There is no electronic override on this family - every shift quality problem is mechanical, which is why a worn bore in the valve body shows up immediately as a pressure or timing complaint rather than a stored code.
GM's own service literature for the THM 400 lists expected line pressure by range - roughly 55-70 psi in Neutral, 60-85 at idle in Drive, climbing to 135-160 psi in D2 and 95-150 psi in Reverse - so pulling a pressure gauge on the line tap before you order tells you whether you are dealing with a worn pressure regulator bore (pressure too high or erratic) or a weak spring and boost valve (pressure sagging below spec). Our TH400 valve body problems and testing guide covers that pressure-gauge procedure in order, and the TH400 fluid type and capacity guide confirms the correct Dexron spec and refill amount before you button it back up.
This listing is built for the TH400 valve body as used from 1972 through 1974, a span that covers GM half-ton and heavier trucks, motorhome chassis, and full-size performance and luxury cars - including the Jaguar and Rolls-Royce applications GM supplied the TH400 to during this era. The TH400 went through numerous valve body and governor revisions across its full 1964-1990 run, so confirm your casting and modulator thread against the listing photos before ordering, or send your application so we can match the right revision. The full TH400 parts collection covers the rest of what we stock for this transmission.
Replace the vacuum modulator and governor weights/springs at the same time you swap the valve body if either is original - a bad modulator will reintroduce the same high-pressure symptom through a brand-new valve body. Torque the valve body bolts in sequence to spec, not corner to corner, and refill with Dexron ATF to GM's published capacity for your case. Because this is a fully hydraulic transmission, there is no relearn procedure - road test immediately after the fill and recheck line pressure at the tap if the shift feel is still off. If testing shows the bore itself is beyond a straightforward swap, a TH400 overhaul kit or a TH400 solenoid kit for later electronic variants covers the rest of the hydraulic circuit.
| Fits | TH400 1972-1974 |
| Part type | Valve Body |
| Condition | Used |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No - the TH400 is fully hydraulic. A vacuum modulator and governor feed the valve body mechanical signals for engine load and road speed, and the valve body alone sets line pressure and shift timing.
A worn pressure regulator bore is the most common cause, and it shows up as burnt converters, crankshaft seal leaks, or friction material failure from pressure that never settles to spec.
GM's service literature lists roughly 55-70 psi in Neutral, 60-85 psi at idle in Drive, up to 135-160 psi in D2, and 95-150 psi in Reverse. Pull a gauge at the line tap and compare before assuming the valve body is bad.
It is built for 1972-1974 production, but the TH400 ran through many casting and governor revisions over its 1964-1990 run, so match your casting marks and modulator thread against the photos or send us your application to confirm.
GM half-ton and heavier trucks, motorhome chassis, and full-size performance and luxury cars - including Jaguar and Rolls-Royce models that sourced the TH400 from GM.
There is no electronic relearn since the TH400 is fully hydraulic. Replace a worn modulator at the same time, refill with Dexron ATF, and road test while rechecking line pressure if shift feel is still off.
