Is anyone using a 904 behind a GIII Hemi?

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70chall440

Mopar or No Car...
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I am in the planning stages of my 68 FB build and am leaning very heavily towards putting a GIII Hemi in this car. The car currently has a 318/904 in it and I am wondering if I might be able to reuse the 904. I want to keep the car AT and intend to use the floor shifter, so as I understand it, I can use a 727, A518 or perhaps the 904.

I know 904's have been used successfully in drag cars and other hard use vehicles but I am wondering if there is some reason not to use it behind a new gen hemi.

This is going to be a driver, it has to be reliable and relatively comfortable.
 
Thanks. I was just wondering mainly because I have a 904 in hand already. I assumed one could be used since a 727 can be used.
 
Ironically, last night I came across a 2010 Mopar Action mag and read an article on a Drag Pak Challenger using a 904. This was a pro built trans and they were only getting between 1 and 40 runs on the trans. Serious racers like the 904 because they have less parasitic loss than a 727 but they have to be heavily beefed up. Just to gain a tenth or two?

A G3 makes good power and torque. Some say comparable to a stock 440 or 426 Hemi because it is SAE not gross rated.

I see rebuildable small block 727s going for $100-200.
If it was me I'd go 727 for peace of mind and you may be able to sell your 904.
 
All good info. I have several 727's and have used them for years so I am familiar with them (have one behind my EFI 6 pack 440 Challenger and one behind my 56 Desoto 330 Hemi in my 52 Dodge PU). I am just trying to determine a plan/path for this A body Cuda. I really don't want to embark on a full build again but I suspect I am going to have to.
 
My 904 Trans behind my 408 Six Pack. Yeah I know what I'm doing. But you do what you think is best for you.

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For a driver with a little power, 904. It's getting to be old wives tales anymore on what that trans will take and won't. GOOD clutches, bands, probably has a 4.2 lever already, good valave body/shift kit, good to go.
 
I am glad to hear it. I was never a transmission guy, I put them in and took them out but I ended up having to do some work on my 727 and began researching it and discovered that while not necessarily simple, it wasn't all that difficult either. That said, I never explored or spent time to understand the differences and nuances between the two. Growing up a Mopar guy, I always heard that the 904 was weak and never to use it behind anything with even moderate power; until I was at a drag strip and there was a guy there using one behind a very radical 340. When I asked him why, he said what everyone seems to be saying now "they are lighter and if built right can take whatever you throw at them".
 
The inside of each are so very similar, they are damn near the same. Once you get inside it, you'll be like, yeah, I got this.
 
I am glad I started this thread and you guys responded, gives me hope :)
 
keep the 904. no need for that boat anchor 727. what kind of power you putting out? 904 can handle quite a bit reliably with some cheap and simple mods along with quality parts and someone that knows what they are doing building it..
 
I am planning on using a nearly stock 5.7 (as soon as I can buy one). I am not looking to build big HP, this is going to be a driver. So as it relates to the HP level, it will be whatever the engine was built as, 350-400 I would guess.
 
**** a 904 all the way man.. little shift kit and some good parts in it. nothing expensive or exotic and that baby will be there for years and years.
 
I'm also planning to use the original 904 for my Hemi swap.
From what I read above I would need a shift kit, new clutches and new bands. But there are many types and price levels, any thoughts on what to go for?

I have a transgo TF-1 kit allready waiting to be installed.
Would a kit like Performance Max Performance Kits PAKT12700 be ok? Seems to only have one band in it though?
 
I have not yet researched what is needed to beef up a 904 but will. Shift kit for sure (easy part) and at least a complete rebuild.
 
I am glad to hear it. I was never a transmission guy, I put them in and took them out but I ended up having to do some work on my 727 and began researching it and discovered that while not necessarily simple, it wasn't all that difficult either. That said, I never explored or spent time to understand the differences and nuances between the two. Growing up a Mopar guy, I always heard that the 904 was weak and never to use it behind anything with even moderate power; until I was at a drag strip and there was a guy there using one behind a very radical 340. When I asked him why, he said what everyone seems to be saying now "they are lighter and if built right can take whatever you throw at them".
In stock form, the 727 is stronger. When the 904 was introduced, the back in the day racers swapped over to the 904 and worked them up making them stronger. Once built properly, they can handle a lot of power. This has been the case ever since and it still seems that no one is catching on to what was done oh so many decades ago.
 
I heard that for years but never really explored it. I do know racers liked/like them because they were/are lighter and supposedly stronger than a 727 when built correctly. The question I guess is what does "built correctly" mean. I do know that 904s were favored by racers in my area growing up because they were easier to find.
 
To most, built "correctly" means throwing an *** load of cash on shiny parts because "that's how it's done". Necessities are a billet low/reverse servo kit, 4.2 lever, rigid kick down band(preferably red lining), and correct clutch pack clearance. I left clutch material out intentionally, because I know I will get slammed on my beief (or what I know has actually worked for me). Even clearances are a thing of discussion. As a rule of thumb, .010-.012 per friction. You can use the thin forwar friction plates in the direct drum to get 5 discs in there. Usual rebuild techniques apply. Inspect everything very carefully. Last, but, not least. A good valve body. Either store bought or a decent home prep with a trans go kit.
 
The question I guess is what does "built correctly" mean.
..it means different thing to different power output.

have a friend that class races and in the 10's. he needs every hundreth of a second from the car and it needs to withstand serious beating.. he has about $5500 onto his 904...

for me i don't need anything like that for a street car that doesn't see the track all that much.. plus my car was only a 12.teen car... 904 was a real basic build.. a friend does them for me.. bolt in sprag, extra clutch in it, alto red clutches, have used different kickdown leavers over the years.. all worked well.. 3.8,4.2 and the 5.0. then one of his home done shift kits.. he doesn't like the kevlar bands so i don't use one.. that trans is well under 1000 dollars and have been very very reliable and should be perfect for a stock 5.7 hemi...
 
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