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727 or 904? #1958653
11/27/15 03:18 AM
11/27/15 03:18 AM
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Minnesota, USA
humpty Offline OP
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Guys - I'm looking to pick up some ET with a tranny upgrade. I currently have a 727 with mostly stock internals aside from the usual upgrades - bands, clutch plates, manual reverse value body and no rollerized parts. I have an 8" custom converter that could stand to be loosened up some (flashes at 4700). My 60' times are mid 1.5's with a 590hp/525tq SB. I'm adding a transbrake this winter, and since I'm going through the tranny when adding the transbrake I figure now is a good time to look at a possible tranny swap. I'm interested in your feedback - where would you spend your money? Invest in upgrading the 727, or change to a 904?

Thanks all!

Re: 727 or 904? [Re: humpty] #1958674
11/27/15 04:44 AM
11/27/15 04:44 AM
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727 with aluminum drum, lightened sun shell is one route you can go. Going to Torrington bearings throughout can help increase durability, but if you truly want a "quicker" trans.... the 904/999 will win. How much you willing to spend? I have a number in my head of what you'd probably lay down for a good one.

Re: 727 or 904? [Re: humpty] #1958684
11/27/15 06:25 AM
11/27/15 06:25 AM
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st.louis,mo.
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what about for a big block

Re: 727 or 904? [Re: humpty] #1958689
11/27/15 09:59 AM
11/27/15 09:59 AM
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Florida
Locomotion Offline
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Chrysler did some testing in the '70's and, with trans and converters built to the same specs, a 904 was about .15 faster that a 727. Naturally, a 727 will be stronger than a 904, but a 904 is less prone to grenading! 904 is popular in class racing with small block Super Stock cars in your HP range and more.

Rollerizing and aluminum components can make the car faster, but ET reduction will be less and cost a lot more for the return. Increasing durability with aftermarket shafts would be a good addition either way.

Big block racers have adapted lighter, custom 727 parts as well as modifying 904 components to fit a 727 case. But that is also VERY expensive.

As in most cases, there is a lot to be found in fine tuning what you have to find ET. Dyno time, extensive carb tuning, custom trans gear ratios, a bunch of converters and rear gears and such is needed if you really want to get everything out of a combo.

Re: 727 or 904? [Re: dart games] #1958704
11/27/15 11:34 AM
11/27/15 11:34 AM
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Originally Posted By 440outlawdart
what about for a big block


ProFlight from Pro Trans.

Re: 727 or 904? [Re: humpty] #1958717
11/27/15 12:07 PM
11/27/15 12:07 PM
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Bowling Green, KY
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cudaboy Offline
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Quote:
but a 904 is less prone to grenading
Why is that? I'm in the market soon for a trans behind my 6.1 and am not sure which to use either.

Dennis

Re: 727 or 904? [Re: J_BODY] #1958751
11/27/15 01:36 PM
11/27/15 01:36 PM
Joined: Oct 2007
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Minnesota, USA
humpty Offline OP
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Good info guys. Very much appreciated!

I'm willing to pay for the increase in performance so let me know what you think it would take. A 904 seems like the right route to go if I can pickup ET, maybe drop some weight (I've heard somewhere around 50lbs) and not give up durability.

Re: 727 or 904? [Re: Locomotion] #1958758
11/27/15 01:47 PM
11/27/15 01:47 PM
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Minnesota, USA
humpty Offline OP
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Good info. I was wondering about the trans gearing. Is there a lot to be gained by modifying the trans gearing? I've heard both good and bad.

Does anyone make a 904 or 727 with an SFI certified bell housing? If not, what's the best shield option? I'm guessing the 904 has a smaller profile leaving more room in the tunnel.

Thanks for the feedback.

Re: 727 or 904? [Re: humpty] #1958775
11/27/15 02:22 PM
11/27/15 02:22 PM
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Tulsa OK
Bad340fish Offline
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My combo is not a great example but the low geared 904 was much faster than a 727.

I had an old clapped out 360 that ran 11.30s on a 150 shot of nitrous. It would run 117mph and a 1.53 60ft. I broke a converter snout so I had turbo action change my converter so I could put my old 727 back in.

It ran 11.5s with a 1.63 60ft with the 727 in it. I was able to get the ET back with more nitrous but I couldn't get the 60ft back.

Now that i have a NA 360 running better than the nitrous combo I really want to put the low gear 904 back in. I think it might be my ticket to the tens.


68 Barracuda Formula S 340
87 "Chrysler" Conquest
Re: 727 or 904? [Re: humpty] #1958791
11/27/15 03:02 PM
11/27/15 03:02 PM
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las vegas
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the 904 front drum does not explode due to the mass of the drum...much smaller..

i got 3 904 that are used for racing they have multiple years of racing. I convert the front drum from a 4 disc/steel to 5 disc/steel by using the thinner disc from the rear drum.

get the 24 multispring kit from A&A, CRT or TCS to replace the large wound spring in the front drum...it is will unwind and let the clutch disc drag at high rpms...

Our fastest car 71 Dart with a 360 has gone 10.31 with a 1.386 60 ft time...

the 904 is 35 lbs lighter with most of that being internal.....

the low gear ratio does not allows produce the fastest times...depends on the weight and torque of the combination.

and back in 1992 i swtiched from 727 to 904 ...picked up .15 and never looked back...

All 3 904 use Tranzact of Inday transbrake...


Tony

70 AARCuda Vitamin C
71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield)
71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas)
71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)
Re: 727 or 904? [Re: humpty] #1958800
11/27/15 03:33 PM
11/27/15 03:33 PM
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Glendora Ca.
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If not, what's the best shield option? I'm guessing the 904 has a smaller profile leaving more room in the tunnel [/quote]

I run a CSR sheild with a 904 like most guys with a stock floor. I suggest you do yourself a favor and roll the seam where the floor meets the firewall in the tunnel flat for some room and test fit the shield and trans with a empty case and adjust (hammer) to make it fit easy, before you load the finished trans in the car. Also it is good to cut the ears and junk off the case before the trans is built.

I don't think most 4" stroke smallblocks with enough rear end gear need a low gear set up, the 2.45 ratio works best for me.



"Just a Bracket car dressed up like a streetcar"
Re: 727 or 904? [Re: 70AARcuda] #1958851
11/27/15 05:50 PM
11/27/15 05:50 PM
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Ambridge, Pa.
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Only draw back on the 904 is the hub likes to crack. I had my hub changed to the the hub with the flats. U have to change the frt support to a a500. Since i changed over, no problems. Also u need a converter with a steel stator. Or this will happen over time.

image.jpeg
Re: 727 or 904? [Re: humpty] #1958928
11/27/15 08:21 PM
11/27/15 08:21 PM
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80arrow Offline
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Originally Posted By humpty
Good info. I was wondering about the trans gearing. Is there a lot to be gained by modifying the trans gearing? I've heard both good and bad.

Does anyone make a 904 or 727 with an SFI certified bell housing? If not, what's the best shield option? I'm guessing the 904 has a smaller profile leaving more room in the tunnel.

Thanks for the feedback.


I'd run an Ultrabell bell housing and a trans blanket.

Re: 727 or 904? [Re: humpty] #1958947
11/27/15 08:55 PM
11/27/15 08:55 PM
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Dayton, OH
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1980volare Offline
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I've been well into the 9s with a 904 @3600lbs.

I'm more worried about the 8.75 with factory 3.23 gears that's in the car breaking before the trans.


Last edited by 1980volare; 11/27/15 08:55 PM.
Re: 727 or 904? [Re: Locomotion] #1959129
11/28/15 08:32 AM
11/28/15 08:32 AM
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Newport, Mi
Evil Spirit Offline
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Originally Posted By Locomotion


Rollerizing and aluminum components can make the car faster, but ET reduction will be less and cost a lot more for the return. Increasing durability with aftermarket shafts would be a good addition either way.



A friend and I argue this point all the time. He spends a lot of money on the roller bearing parts because he feels he needs them. 650 hp, 2950 lbs, low gear set 904 w/brake, mid 9 second Dart. Since the car doesn't ET any quicker, and we weren't knocking the thrust bushings out before, I never saw a need for the high dollar parts, especially in a bracket car. In fact, we have had more issues from running aluminum drums than from everything else. IMO You can reduce HP loss more by being able to reduce line pressure with good friction materials than you can by rollerizing. Again, IMO, money is spent better in a better converter than by rollerizing parts.


Free advice and worth every penny...
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Re: 727 or 904? [Re: humpty] #1959133
11/28/15 09:39 AM
11/28/15 09:39 AM
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Jerry Kathe Offline
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For the most part, I would have to agree with Evil Spirit.If this is a bracket car, save your money on the rollerized stuff and aluminum drum, those drums require way too much maintenance. If this is a transbrake application, use a brake with low band apply(LBA) in addition to a good quality sprag. If you have to use a trans brake that does not have LBA, then still use a good quality aftermarket sprag, but use the billet steel drum.

904's still use a powdered steel drum from the factory, my guess is that the quantity of failure's are only due to quantity of 904's with non-LBA trans brakes being used. If the sprag fails, it is still RPM x low gear ratio exposed immediately on the drum - disaster waiting to happen.

Re: 727 or 904? [Re: Jerry Kathe] #1959159
11/28/15 12:09 PM
11/28/15 12:09 PM
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Mt Morris Michigan
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dont want to rob the post, but if the sprag fails with low band apply, would the low band hold rear drum and prevent front drum from spinning out of control?

Re: 727 or 904? [Re: humpty] #1959205
11/28/15 01:49 PM
11/28/15 01:49 PM
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Few years back I swapped from a 727 to a full roller 727 with aluminum drum, lightened sun shell, etc, etc in at the time a high 9 sec car. I saw zero on the time slip with the swap.
My current car I stripped the axles at the hit with a 904, pulled the tranny apart and there was no damage, everything was fine.

Last edited by B3422W5; 11/28/15 01:49 PM.

69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight
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Best so far, 10.40 @127 1/4
1.41 best 60 foot
6.60 at 103.90 1/8

Re: 727 or 904? [Re: humpty] #1959210
11/28/15 01:52 PM
11/28/15 01:52 PM
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Minnesota, USA
humpty Offline OP
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Thanks for the replies everyone! Looks like I'm making the swap to a 904. Any good shops in the Midwest you guys trust?

Re: 727 or 904? [Re: humpty] #1959218
11/28/15 02:10 PM
11/28/15 02:10 PM
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PA.
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Originally Posted By humpty
Guys - I'm looking to pick up some ET with a tranny upgrade. I currently have a 727 with mostly stock internals aside from the usual upgrades - bands, clutch plates, manual reverse value body and no rollerized parts. I have an 8" custom converter that could stand to be loosened up some (flashes at 4700). My 60' times are mid 1.5's with a 590hp/525tq SB. I'm adding a transbrake this winter, and since I'm going through the tranny when adding the transbrake I figure now is a good time to look at a possible tranny swap. I'm interested in your feedback - where would you spend your money? Invest in upgrading the 727, or change to a 904?

Thanks all!




I hope you aren't sorry a year from now if you switch over to a 904. Before you give up on the 727 have your 4700 stall converter raised to 5500-5600 and you will go a lot faster. Been there, done that.


1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

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