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Determining between th350 and th250...


Guest Twilight Fenrir

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Guest Twilight Fenrir

Hello,

I've got a transmission of unknown origin in my El Camino. The pan is the square with a missing corner, and 13 bolts, making it either a th350, or th250. From what i've been able to find out, the only way to tell the difference withoit taking them appart, is thatthe 250 has a band adjuster on the outside.

My question is thus: what does this look like? And where would I find it if it were there? If it matters, mine is one of the ones that has both chevy, and bop patterned bellhousings.

Thanks

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If the trans has not been rebuilt, especially by a mass rebuilder, there should be a square tag on it (possibly on the passenger side?) which has the "code" on it. Usually two letters, possibly three on the later models.

The THM250 is DEFINITELY the lower torque capacity of the two! I believe the band adjuster bolt is on the passenger side, too. It should be obvious. There should, I suspect, be some online pictures of both of them.

Just some thoughts,

NTX5467

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Guest Twilight Fenrir
Picture at . . . craig.backfire.ca/pages/autos/boxchevy/th250

Enjoy!

NTX5467

Awesome! I tried searching for such a picture but I could not find one. Thanks a bunch! I'll go out and take a peak tomorrow to find out.

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Guest Twilight Fenrir

Well crud... I've got a TH250... Yeah, I never would have found that without that picture.

Oh well, it will still do what I need it to do until I can figure out what kind of manual transmission I want to stick in there. Thanks again!

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In some cases, the lower torque capacity transmissions can give decent service in higher-power places they weren't designed to be . . . so long as the torque shock loads are not too great or prevalent.

Back when it was something of an accepted orientation that a front wheel drive car of the 1980s could not transmit more than 200 horsepower past the flywheel, when engine power started creeping upward (competitive forces from competitors to have more horsepower), the way they started getting by with the "weaker" transaxles was "electronic intervention". With an upgrade in computing power of the ECM, which also knew what the transmission was doing, they would program the ECM or PCM (in later times) to back off of the engine's spark advance during the split second the transmission was shifting, then return it to normal after the shift was completed. Such "torque management" (the current term for it) became "the norm" in almost every vehicle, for smoooother shifts and longer transmission life. Now that we also have electronic-controlled automatic transmissions, they can also modulate "apply" pressures better than in prior times, for enhanced smoooothness and such.

What this has done in many newer 6-speed applications, where the 1st gear is approx 4.50, and second is approx 2.50, is make the heavy-throttle 1-2 upshifts feel VERY wimpy. It's possible that some aftermarket "tuning" can result in a more satisfying firm shift, but with the factory calibrations, it just feels sick, to me. But some don't feel that bad to me, either . . . a variable situation.

Sorry about the THM250 . . .

Enjoy!

NTX5467

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