1974 Duster 340 Engine and 727 Transmission Questions!!!

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DaWeezzz!!!

DaWeezzz!!!

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Here I go with my 1st post...

I have the following a 1974 Plymouth Duster with a 318 engine and 904 Transmission.
IMG_4136.JPG


The 904 Transmission measures around 31 1/2 inches long.

I purchased a 1973 340 Engine, 2780930-340-7. Engine # 3B392420. Date 02-08-73.
00w0w_c3ML3z1DHx2_1200x900.jpg

I also purchased a 727 Transmission that measure 25 inches from the top of the case to the bottom where the silver ends, PK4028406 5423 2135.
20200721_125457.jpg

Is this set up going to work or do I need to find a different 727 Transmission that's longer?

Also found another 727 Transmission PK322277 4546 9495 that came out of a motorhome. Will this work with the 340 Engine?
00S0S_kqIVhshukc3_0t20lM_1200x900.jpg

Or should I stick with the 904 Transmission that in the car right now and connect it to the 340 engine? Everyone is telling me to go with the 727 Transmission. Ok but with one?

So confused with these 727 Transmissions!

Keep in mind, both 340 Engine and 727 Transmission are both being broken down and completely rebuilt with all new parts. Just wanna know I have the right 727 Transmission BEFORE I start all the work. Let me know. Thanks...

Alec!!!
 
I would stay with the 904. Its lighter & draws less parasitic power than the 727. If built with quality parts with attention to tolerances, it will handle anything a 340 can throw at it. Plus you wont have to change the drive shaft.
 
727 is a better transmission but for the 340 the 904 will handle almost anything if built or rebuilt with the 340 in mind.

also the 904 will give you more clearance and same drive shaft. If you go that route. The 727 if built well is a fantastic transmission but heavier, physically larger and in an later a-body like a 67-76 makes exhaust fit ment a tad tougher.
IMHO.
 
If you put big tires on it, or a traction device, the 340 might start breaking the 7260 U-joints.
But with 245s or less, yur good. Hopefully you have at least an 8.25 rear end with hopefully at least 3.23 gears

As for those 727s; either will fit just by changing the output shaft and tail, to the P-car length; no big deal.
Also no big deal is to upgrade the 904 for use with the 340. The 1973 model 340 is (or was), a low-compression iteration so its torque output is gonna be easier on everything behind it. But the 340 cam likes at least 3.23s and a higher than 318, stall.

Having said that, there is nothing to stop you from swapping the 340 cam out, in favor of something more streetable, to work with the 318 stall and gears. I'll tell ya; a 340 with a 318 cam is a pretty stout performer; it cures the soft bottom end of the 318, makes plenty of midrange, and gets great gas-mileage. It just lacks the 340 top-end rush, which with 2.76s you would never get to enjoy anyways until over 80/closer to 90mph, in second gear/ Jus saying.
Yes I already built such a combo, and now,45 years later it still remains one of my favorite all-time street combos.
Oh yeah, the 318 cam has ZERO idle lope, so your friends will never believe you when you say you have a 340..... until you fly by them in second gear.
You will need a "posi".
 
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904 with good performance/race parts will be fine. A quality 7260 u-joint, like Spicer, will also work well. (I've run Spicer 7260 solid u-joints in my 360/904 race car for years without issues.) As mentioned earlier, 904 takes less HP to turn, so you'll be faster. (About .15 in the 1/4 based on '70's Chrysler testing between 727 & 904 - all else being equal.) A 904 also doesn't grenade the drum like a 727 when something goes wrong.

You will need a special B&M flexplate to mate the neutral balanced 318/904 converter to the externally balanced cast crank 340.

The short 727 likely is out of a truck or van.
 
Your 340 has a 69-down water pump and timing cover so that water pump won't work with your 74 radiator.

Look at the front of the damper, there should be a cast counter balance ring on the pulley mounting side that says "Use with 340 Cast Crank Only". If it doesn't have that then hopefully your crank is neutral balanced. Did you get any info from who you bought it from?

Unless you got 340 A-Body mounts with the engine, one of your 318 mount will need modified to work on the 340 block.
 
That long tail 727 won't fit a 340, but you can use the tailshaft, ts housing and front planetary in the short one. Both are probably heavy duty with four direct clutches tho cuz mh's and trucks and amc's used a four plate direct. take them both apart but remember to keep the two front drums with their respective pumps.
 
I took out my 727 behind a 340
To put in a 904.
Mine has the low gear set and helped bottom end a lot vs the 727...
I'd stay with your 904
 
KickDown said:
I would stay with the 904. Its lighter & draws less parasitic power than the 727. If built with quality parts with attention to tolerances, it will handle anything a 340 can throw at it. Plus you wont have to change the drive shaft.
Click to expand...
Thanks for the info. Based on all the replies. looks like the 904 is the way to go... Alec!
 
Syleng1 said:
727 is a better transmission but for the 340 the 904 will handle almost anything if built or rebuilt with the 340 in mind.

also the 904 will give you more clearance and same drive shaft. If you go that route. The 727 if built well is a fantastic transmission but heavier, physically larger and in an later a-body like a 67-76 makes exhaust fit ment a tad tougher.
IMHO.
Click to expand...
Thanks for all the info. New to this game and that info helps out big time! Alec...
 
AJ/FormS said:
If you put big tires on it, or a traction device, the 340 might start breaking the 7260 U-joints.
But with 245s or less, yur good. Hopefully you have at least an 8.25 rear end with hopefully at least 3.23 gears

As for those 727s; either will fit just by changing the output shaft and tail, to the P-car length; no big deal.
Also no big deal is to upgrade the 904 for use with the 340. The 1973 model 340 is (or was), a low-compression iteration so its torque output is gonna be easier on everything behind it. But the 340 cam likes at least 3.23s and a higher than 318, stall.

Having said that, there is nothing to stop you from swapping the 340 cam out, in favor of something more streetable, to work with the 318 stall and gears. I'll tell ya; a 340 with a 318 cam is a pretty stout performer; it cures the soft bottom end of the 318, makes plenty of midrange, and gets great gas-mileage. It just lacks the 340 top-end rush, which with 2.76s you would never get to enjoy anyways until over 80/closer to 90mph, in second gear/ Jus saying.
Yes I already built such a combo, and now,45 years later it still remains one of my favorite all-time street combos.
Oh yeah, the 318 cam has ZERO idle lope, so your friends will never believe you when you say you have a 340..... until you fly by them in second gear.
You will need a "posi".
Click to expand...

Thanks for the great info!!! 340 Engine and is gutted. Replacing with all Edelbrock parts, Hydraulic Roller Lifters, New Heads, Performer 318/360 Intake Manifold, Etc... Alec!
 
DaWeezzz!!! said:
Thanks for the great info!!! 340 Engine and is gutted. Replacing with all Edelbrock parts, Hydraulic Roller Lifters, New Heads, Performer 318/360 Intake Manifold, Etc... Alec!
Click to expand...

You may want to consider the Performer RPM. The standard Performer will restrict the 340, especially with any additional mods above stock.
 
The guys at A-1 Racing Transmissions told me years ago they could build me a 904 that would handle just about any small block combination I could put in front of it.
 
Unconventional said:
The guys at A-1 Racing Transmissions told me years ago they could build me a 904 that would handle just about any small block combination I could put in front of it.
Click to expand...
My ex-employer ran a B Altered Automatic race car. Power from Steve Schmidt(500 cu. in Chev) about 1200HP. Transmission 904. Best et, 6.9, speed, over 200MPH. Once held the NHRA record for his class. And yes the transmission held up.
The company he owned, developed many and manufactures many transmission parts for the racing/performance industry. His race car was the test mule for the products they make.
 
Sure and you can even run a C4 behind a 460, but I'm on a budget. If you want to do it once and build a stock hd trans, then the 727 is worry free. A 904 will require hd parts, whereas a stock 727 is stronger than a built 904. Parasitic drag?? If you need an extra 2/5 of a second in the quarter, then by all means throw your money at a 904. I guess I'm just tired of advice touting the "great" 904, which was originally a "TF6", and was never available behind a big block...for a reason. In this day and age, if you want more gear, it's time for a 518.
 
a 904 doesn't need anything exotic in it to hold up to quite a bit of power.. just quality parts and build by someone who knows what they are doing.. i've been running 904's and beating the hell out of them in my cars for close to 30 years now... they hold up and hold up awesome.. hell the one that is in our dart now is one i had build in 2004 or 2005 and beat the hell out of on the street and track in my old yellow dart. then i lent it to a friend with a 11.50 cuda and he ran it a couple years before going modern hemi and OD. was flawless for him too..... when building our existing dart i had it freshened just because everything else was fresh.. once apart my buddy who rebuilt it way back when said it didn't really even need to be done. looked great inside...

CudaFactHackJob said:
In this day and age, if you want more gear, it's time for a 518.
Click to expand...

**** i'd run a a500 before a 518. in all honesty i wouldn't run any of the mopar OD garbage.



.
 
Chrysler is the only car company that runs their own overdrive behind their most powerful diesels. No GM overdrives can hold up behind a stout diesel, but Chrysler's are based on the 727. GM diesels are running Allison transmissions. 904's are racing transmissions because you can run a lower first gear than a 727; that's about it. And I don't know where you're going to find a competent 904 builder; they're not on every corner. You can throw a 727 together and not worry about it, but a 904 has to be done very carefully by a reputable tranny mechanic. A bunch of parts for under a hundred, or $1500 to a pro...it's a no brainer.
 
my 904's are nothing exotic or expensive at all.. good clutches, home built shift kit and bolt in sprag... nothing special.. they work and they hold up... pretty simple decision to me.. you keep playing with that boat anchor 727 though. leaves more 904's for the rest of us to play with.
 
Then build it for him. And hand him $500 for that bolt in sprag, heavy duty clutches and bands, direct drum return spring kit, hd servo, etc...not the program for the budget builder. But he can do a 727 himself with what he has there for probably under $25. That's the cost of a reseal kit and filter. Redrill a couple holes in the separator plate and go racing. Put the money in a converter, not some giant thing out of a New Yorker. But lots of 3/4 ton trucks have high stall converters when they run low rear gears. Spend the saved dollars on the rearend.
 
bold in sprag is nowhere near 500 bucks.. quality clutches aren't very expensive either.. hey if you or your trans guy doesn't knwo how to build a 904 thats cool.. but don't try to say they are expensive or won't hold up. that 1950's thinking is just that.. its 2020 and there are far better options then that boat anchor 727 these days.
 
That's NOT what I said. I didn't say that a bolt in sprag is $500. How much did your parts cost for your build? Maybe you got plenty of money to spend on a race car trans, but most people on here don't. All anybody has to do to understand the difference between a 904 and a 727 is to place a clutch plate from each one on top of the other. We're not talking about a small difference...it's tiny compared to gigantic. The 904 was never available behind the 340 from the factory. The only time I would recommend a 904 is in the early pre-67 A body because of clearance issues at the top sides of the bellhousing. I have one in my 66 with the low gear set. But I build trannys so it was cheap for me to put together. But this guy has a later A body and TWO 727s...Bolt in with factory parts. Oh, and don't even get me started on those junk thin walled converters that crack. I just don't like to see folks have problems down the road because they made a choice that I think is not in their best interest.
 
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