SKU: HUGGM25HD
MPN: GM25HD
The Hughes Performance GM25HD is a 2500 stall torque converter built for GM TH350 and TH400 automatics running a 30-spline input. Hughes Performance came up through drag racing transmission work, and that background shows in this HD Series unit aimed at the street/strip crowd. It raises stall over a factory converter to put the engine into its working power band right off the line, which clears up the slow, sluggish launch you get with a stock th350 torque converter behind a warmed-over engine. It's a sensible match for stock to lightly modified small and big block combinations that still need to idle in gear and drive on the street.
The converter carries a 10.75 in. bolt circle to match the standard GM flexplate pattern and a 30-spline hub for TH350 and TH400 input shafts, per the published specifications. Hughes rates it at roughly 2500 stall, though actual stall varies with engine output, cubic inches, gearing, and vehicle weight, so treat that figure as a target rather than a fixed number. The HD Series construction is built for the higher loads that come with more aggressive cams and added power over stock. Shipping weight runs about 23.61 lbs. If you're refreshing the whole transmission at the same time, it pairs naturally with a TH350 transmission kit or the matching TH400 transpak for a complete rebuild.
This converter fits the builder who wants quicker, harder launches without losing street manners. Behind a stock-to-mild engine it wakes up off-idle response and lets the motor pull from a higher starting point, which helps with heavier cars and steeper rear gears. Verify your flexplate bolt circle and input spline count before ordering so the converter mates correctly to your TH350 or TH400. When you're planning the build, browse our full drivetrain parts for the bolt-on hardware and rebuild components that go with a converter swap.
It's built for GM TH350 and TH400 automatic transmissions with a 30-spline input shaft. The 10.75 in. bolt circle matches the standard GM flexplate pattern. Confirm both your spline count and bolt circle before ordering so the converter mates correctly to your setup.
No. Hughes rates this converter at roughly 2500 stall, but actual stall speed shifts with engine output, displacement, camshaft, rear gearing, and vehicle weight. Treat 2500 as a target. A heavier car or milder engine usually stalls a touch lower than the rating.
Yes. The HD Series is recommended for stock to slightly modified engines and still lets the engine idle smoothly in gear. It raises stall enough to sharpen launches while keeping normal street drivability, which is why it suits street/strip cars rather than full race-only builds.
Not strictly, but a converter swap is a natural time to refresh the transmission. If your TH350 or TH400 has miles on it, pairing the converter with a rebuild kit or transpak helps the unit handle the added load that comes with a higher stall and more power.
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