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Would like some transmission advice

73CudaMan

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Hi: Believe it or not, I am the original owner of a 73 Barracuda 318/904. I am in the process of rebuilding a 70 340 with 71 heads (2.02 intake valves). I am agonizing on what to do with the 904: I can get hold of a 727 with 2700 converter for reasonable money. Not sure of what the change from 904 to 727 entails: some say stock trani crossmember is ok to reuse, others say must change. And what about linkage of 904 versus 727. I know all about the fact that I need a shorter driveshaft.
I brought the car to a reliable trani shop and they advised me AGAINST putting in the 727. They would get the 727 rebuild job or 904 rebuild job anyway, so I think the guy was honest. This guy builds racing transmissions so he knows his stuff. My car will just be strictly for the street. He claims due to the lighter 904 weight and the 727 conversion issues, the 904 is the way to go. He claims 904 will be good for 500HP and I will be in the 400 HP range. Do u recommend beefing up the 904 or hassling with 727 conversion (cross member, linkages, driveshaft issues)?
 

RJH

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40 years ago, you would have to of switched over to the 727 tranny. Nowadays I,m not so sure?
 

340challconvert

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Here is some 904 vs 727 information I have saved; opinions from some different sources:
Hope it helps?

What are the major differences between A904 and A727?

They are basically the same transmission except for the size of the parts. There are very few differences in them and they work exactly the same. The 727 was first introduced and then the time came that they needed a auto trans. for a 6 cyl. that didn't need to be as beefy so they made a little version of it known as the 904 or TF-6 as they were called in the old days. Later on they started using the 904 on small blocks.

The 727 sucks up 20 HP more than the 904 because of the larger rotating parts according to Car Craft dyno tests. The 904 can easily be built to handle over 300 HP with the current parts out in the market. It weighs about 30 lbs less.

They are a little more difficult to find, require a new driveline and linkages. Just more $$.

The valve bodies interchange between the 904 and 727, The 904s don't seem to blow up like the 727 has a reputation for (probably due to the weight of the parts as the design is the same).

In stock form a 904 has no problem handling 300 hp and with just upgrades to the friction linings and the installation of a good shift improver kit will handle 400+ hp.

the clutch pack springs and way they take up the end play thrust. the only thing that really interchanges is the valve body. Everything else looks the same but the 904 parts are smaller.

Good point on how much extra power it takes to spin a 727. That's why I always use a 904 until the HP power gets above the practical level of it's capabilities. You can change a bunch of parts to make it handle 600hp but that gets expensive pretty quick.

The reason you don't see as many 904's blown up is probably due to them having a bolt in sprague from the factory. An upgrade necessary to the 727 when building a perf. trans.

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Adam

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Depends on how you plan on driving it on the street, but I think a built 904 would be fine, no problem. Plus you don’t have to get a new driveshaft.

If you go 727, the shift linkage will work, but the kick down will need to be changed; the crossmember will work; the cooler lines are different, if I remember correctly.
 

aussiemark

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If you are going to rebuild the 904 then it will be fine I will be doing the same swap with my very original Challenger soon. I even had a 727 in the shed but sold it to a friend and decided to stick with the original 904 behind the 340 for the reasons mentioned above plus it is the matching numbers transmission for the car so I am happy to leave it in there, the 318 is the original engine so it will be stored away.
 

73CudaMan

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Thanks...this is EXACTLY the position I am in. Some tell me the 727 can use the 904 crossmember and original shift linkage and I need only change kickdown and account for the cooler lines and driveshaft. Then some have verbally told me I have to change the crossmember and I have to change the shift linkage for the 727. Someone out there must have done this 904 to 727 conversion for an E body. If I decide to make the car more of a 73 340 Cuda clone, I should go with the 727. If I want to save a few $$, I do believe the beefed up 904 will be fine. If I knew the real situation as far as the cross member and shift linkage, I would be able to make a better decision, because I do not have limitless funds to do this project. Thanks in advance to any who respond.
 

moparleo

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Just a driveshaft change/alteration and $30.00 cooling lines. Seems that every body talks like you are building a race car. The 727 is one of the most bullet proof transmissions ever built. Don't do a lot of 3000 rpm neutral drops and you won't have to worry about breakage. The factory didn't put 727's behind every 340 just to sell transmissions.
 

rogue

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my 71 challenger was an original 318/904 car... it now has a 360/727... i used the same cross member and shift linkage to the stock slap stick.
 

73CudaMan

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Hey rogue, what did you have to do to the kickdown? I appreciate any experience you can offer...Thanks
 

73CudaMan

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my 71 challenger was an original 318/904 car... it now has a 360/727... i used the same cross member and shift linkage to the stock slap stick.
Hi, what did you have to do to the kickdown? Please advise...Thanks
 

rogue

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i'm running a manual valve body which runs at full pressure so no kick down required... you'd have to switch to a set up correct for the trans or use an after market cable solution such as lokar makes
 

73CudaMan

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i'm running a manual valve body which runs at full pressure so no kick down required... you'd have to switch to a set up correct for the trans or use an after market cable solution such as lokar makes
Thanks
 

73CudaMan

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See attached picture. I have another question. The 727 I can get is part number PK4039537 5870 2410. It was built Tuesday Aug 23,1977. It is for a "truck, long". I found out it came from a Dodge van. Two concerns: is the truck 727 geared differently than a car 727? The other question is since it is "long", does that mean it is even longer than a car 727 which has a length from the bell housing to the end of the tailstock of 34.39" ? I know I will have to shorten my driveshaft from my 318/904 layout, but will the "long" van trani screw me up?

pic for forum.jpg
 

73CudaMan

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It even gets more confusing because for the truck 727s there are short rear timing, medium rear timing and long rear timing. What does rear timing mean? Then there is truck short and truck long (without any reference to rear timing). Will the "truck, long" 727 with the above part number work for me where my 904 trani cross member can be reused and I only have to cut the driveshaft down?
 

73CudaMan

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Sorry more questions: will my 904 "car" slap stick rod gear linkage and 318 kickdown rod linkage work for a "truck" 727 trani? As noted above I will be replacing the 318 with a 340 but I am hoping to reuse the throttle rods and kickdown rods...but now this "truck" 727 trani has me wondering.
 
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