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904 vs 727

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speed_is_addictive View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote speed_is_addictive Quote  Post ReplyReply Direct Link To This Post Topic: 904 vs 727
    Posted: Apr/27/2018 at 6:26pm
My hornet came with a 904.

i will be running a stout 360.

is this trans able to handle the power built properly or should i just invest in a 727. . .

im new to amc but not to power or drag racing. . .

thanks
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gremlin1945 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gremlin1945 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2018 at 7:07pm
 A well built 904 will handle anything you'll throw at it, and it's lighter and smaller than a 727, a consideration installing it in a hornet/gremlin.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote matty 401 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2018 at 9:08pm
was it from a 6 cylinder or a 304 
72 matador 401 the beast
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68 Rogue 360
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speed_is_addictive View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote speed_is_addictive Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2018 at 9:57pm
hmmm, how do i tell the difference. . . 
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gremlin1945 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gremlin1945 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2018 at 10:07pm
If you're putting it in without doing any rebuild I wouldn't do it you will have to have it rebuilt to the specs for high performance use a lot of guys run them and they don't have a problem with them it's not cheap though
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2018 at 7:09am
a 304 runs a 998. which is a beefier 904.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Apr/29/2018 at 11:25am
They put small case 9xx series transmissions behind race Hemi's so they can be built to take the heat.
Racers even run 9xx series internals in 727 cases to cut down on weight/drag,
so the small case parts can be made to live.

If your Hornet is a 1970, the 9xx case would have been swapped from a 72 or later AMC (assuming it's an AMC case),
so you'd want to identify it to be sure what you have.

9xx series transmissions are also easier to get with the 2.75 low first gear,
if you want to run a little taller rear gear,
 the deeper first can help compansate, while still giving you a good gear to launch from.
The 2.75 first for a 727 is much more difficult to get, and expensive.

An AMC 360 with a 904/998/999 is a good combination.

IIRC, the 999 was actually originally introduced when the Chrysler 360 came out,
to handle the extra torque without going to a 727.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2018 at 11:01am
I used to argue that the cost to beef up a 904 or 998 to take the kind of power that even a mediocre 727 will handle wasn't worth it.  I still think so today but less strongly.  If durability is your number one concern, then the 727 is still the best choice.  But the rotational inertia of the smaller transmission is much less and frees up a lot of power.  When I switched to a 998 from a 727 in a 360 American I picked up a couple of tenths just due to the rotational inertia improvement.  One thing that isn't obvious when comparing the bigger clutches of the 727 to the puny clutches of the 998 is the quantity.  Typical 727 has 3, maybe 4, and it takes some work or the right drum to get 5.  Basic 998 has 5 already.  Smaller clutches, but more of them so I would call it a wash.  A second advantage to the 998 is that Chrysler made a lot of low gear planetary 998 transmissions and you have a decent chance of finding a low gear ratio where the 727 low gear planetary seems rare and/or expensive.  That same 998 is now behind a 401 and we will see how long it lasts.  Went 5 years without maintenance behind a 360.
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