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Discussion Starter #1
I know this is a lot to ask for but I’m looking for the cheapest automatic transmission option for a 500hp 12v Cummins I’m putting in my square body Chevy, now I am considering buying the th400 to 12v adapter plate because the th400 is a strong and cheap transmission but the adapter plate is $1,000 alone, but then I could get a th400 used for about $400 totaling in $1,400, my question is...Is there a cheaper option for an automatic dodge transmission that I can get used and upgrade that will hold up just as well for under $1,500?
 

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What are the specs in the square body? Is it a crew cab LWB 4x4? What are you using it for?


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I know this is a lot to ask for but I’m looking for the cheapest automatic transmission option for a 500hp 12v Cummins I’m putting in my square body Chevy, now I am considering buying the th400 to 12v adapter plate because the th400 is a strong and cheap transmission but the adapter plate is $1,000 alone, but then I could get a th400 used for about $400 totaling in $1,400, my question is...Is there a cheaper option for an automatic dodge transmission that I can get used and upgrade that will hold up just as well for under $1,500?

Don't get me wrong the TH400 is a good trans (I've used them behind big blocks in nitrous drag cars), but are you sure you want to put a three speed without a lockup torque converter behind a 12 valve? For all the awesomeness that is the 12 valve , its pretty limited on usable RPM power band without a lot of modification. Considering you're asking about a budget transmission, I'm guessing you're not looking to speed the kind of money needed to make the 12 valve rev (and have power doing it) to 5K RPM.
If you're determined to have an automatic, I'd look for at least a four speed with a lockup converter for a street application.
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Cheap and diesel performance are strangers to each other. At 500hp you will have to upgrade any transmission other than what exists in a 500+hp semi with a tremendous amount of gears and a huge size.
 

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Between $3500-5500, there are a lot of transmission threads I can try and find some. You really are in Triple disk, billet input, HD flexplate territory. Mine was a 2WD so I’m not sure what needs to be beefed up for the tcase.


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Discussion Starter #9
Damn ok that’s a lot more expensive than I thought it would cost for just the transmission, so you think I should go back to the th400 and put a lockup converter in it?
 

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Damn ok that’s a lot more expensive than I thought it would cost for just the transmission, so you think I should go back to the th400 and put a lockup converter in it?
If you do a lock up in that unit you're going to need to do essentially the same upgrades. I'd stick to the 47RH.

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Damn ok that’s a lot more expensive than I thought it would cost for just the transmission, so you think I should go back to the th400 and put a lockup converter in it?
A mechanic once told me.... cheap, reliable or fast. Pick two. If you want cheap and reliable reduce your HP goal. A 400hp trans is much cheaper than a 500hp trans build.
 

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A mechanic once told me.... cheap, reliable or fast. Pick two. If you want cheap and reliable reduce your HP goal. A 400hp trans is much cheaper than a 500hp trans build.
I think people don’t understand what 500hp really is. These truck are damn powerful at 500hp.
 

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Damn ok that’s a lot more expensive than I thought it would cost for just the transmission, so you think I should go back to the th400 and put a lockup converter in it?
I’d agree with what others said, if you can scale back down to 400-450hp you can get by with a cheaper build. Essentially once you are past 450hp you have the same build up to 700ish.


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A 400hp 47rh or re will cost around $1500 if u do it urself 500hp plus will cost you $2800 if u do it urself.
 

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Discussion Starter #16
Ok I’m fine with 400hp, what are the modifications to the 47re that cost $1,500? Because I was planning on doing it myself anyways.
 

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Ok for a 400hp trans. Ur going to need a dpc single disc converter its $495. Go on Ebay there's a good rebuild kit on there for the diesel. It's around 600 or so for the kit comes with the good gpz clutchs. And all the good servos. Get a flex on ebay there like $90. Than get a transgo. Its $65. When u put the kit in do not grind the 4land spool valve or file the notch at the manual valve. For the lock up holes take them to I think its .091 I believe I can put up my copy if u want me to. It took me years to find the stuff for valve no one wants to give out info.
 

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What r u going to use a 47rh or 47re. The 47re are easier to find.
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Also get a atsg manual follow it to the t. But for direct drum clearance try to get it to .100 or close to it.
If u want a really good rebuild kit call goerend it's more money I think around $900 but comes with a book and some other stuff to help u rebuild it.
 
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