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Discussion Starter #1 (Edited)
Does any body know the difference between these 2 torque converters?

I am thinking that I should go with the blue one because the blue one is bigger and bigger is better. This holds true for most things in life.

The blue one says gm 4M on it and has a 6 stamped in the housing. No markings on the black one. It's going into a TH400 on a 455.



Thanks.
 

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I believe that the smaller the converter the higher stall it will have. Think once you get to a 10" converter the stall is around 3,000. So unless you have a big cam in your car dont put the smaller one in. You shouldnt put eighter in untill you know what the stall is on it and what powerband your engine is built for. I think your rear end gearing is a factor also. More knowledgeable guys on here can give you more persice advice i just know the basics. And with converters technicly smaller is better/racey. Good luck
 

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:agree

Give some specs on your combo, aprox HP, gears, weight of car all have an effect on converter selection.

The torque converter can have major performance impact if it is correct/incorrect.
 

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Discussion Starter #4
I wish that I knew more, but I bought this car off of a guy that told me it had a '67 389 in it. (didn't even make a 389 in 67).

From the head casting number, it has a 72 455. It sounds like it has a cam due to the loppy idle, but it hasn't really impressed me with its power. I am guessing around 350hp.

I am looking to smoke the tires once in a while, but will mostly be driving around town.

The 13" blue one is what was in the transmission that is being replaced. The 12" black one came with the transmission when I bought it off of craigslist. He had that on a '66 389.
 

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I'd run the smaller one.

Maybe consider running a trans cooler if you don't have one, smaller converters tend to build more heat in the trans due to slippage.

Look in the converter and see if there is any metal shavings or if it smells "burnt". Maybe even consider having it flushed out at a local transmission shop.

12" converter is probably perfect for your car, If it was a 10" I would say no way.
 

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Discussion Starter #6
Thanks for the help. Any idea what stall I should be shooting for?

I do have a integrated trans cooler in what looks to be the origional radiator, but I am thinking of pulling it out and bringing it somewhere to make sure it is not obstructed. The fact that the current trans was burned out could be a clue that something else is wrong.
 

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Consider adding an external trans cooler and maybe a trans temp gauge too. You can hook the temp gauge up temporarily if you don't want to leave it in the car.
 

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Discussion Starter #8
Got the new tranny installed with the smaller torque converter. It really did make a big difference. I spun the wheels in front of my house without even trying and the $250 craigslist tranny shifts nice and strong.

The car had a TH375 so I am suprised that the one tranny that I deciced to go look at also turned out to be a TH375. I think that I got out of that one as cheap as possible.

It was also a good experieince doing it myself which saved me about $350. Even if it did take me a year to get around to it.
 

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That's what it's all about. And the more you 'do', the more you can do. You rise to the challenge, learn the ropes, and there is huge satisfaction in a job well done that you did. You get bragging rights (if you're the type!) and my favorite: you save money!!
 
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