904 vs. 727 For A Small Block; Big Differences Strength-wise?

[Road_Runner]

In my reading I see that the in 1973 the only V8 the 904 was paired with was the 318-2V, and the 340 got the 727.  I figure this is primarily for strength purposes, but is the 904 really too weak to handle a decent 300-350 hp small block?  Does anyone here run a 904 with a stronger small block? Any issues?  For now I'm just hopping up my 318 with a 4 bbl & better exhaust, but a stronger 340/360 may be in my future.

Thanks in advance, Jim

[71chally416]

The 904 is the tranny of choice for all the fast small blocks in racing. Like the Powerglide, it uses less HP to operate. It also has a cheap 2.74 low gear available. I have one behind my 416 that made over 500hp on the engine dyno that was built by Dynamic in Delaware along with their 9 1/2" convertor. A good article>

http://www.moparmusclemagazine.com/techarticles/drivetrain/mopp_0210_street_strip_torque_converter_test/index.html

[Aussie Challenger]

 Leave the 904 behind the 318 it will perform very well.   
 The money saved you can put towards a 727 for that special 340 or 360 and it can be tailor made for that build up.   

[dodge freak 2]

But the 904 needs to be beefed up to live behind a healthy small block-even a 318.

Just use it but when it fails and it will as you hop up the hp don't let any old shop rebuild it--take to somebody who knows how to strength the trans.

[bb71challenger]

I know 904's are tough but I like the peace of mind that a 727 provides. There is a reason they put them behind stout small blocks and all the big blocks. I would not got crazy looking for one though, wait for a cheap core or well priced one to pop up.

[71chally416]

The 904 I had in my old 68 cuda was an OEM tranny from a '72 318 Challenger. I just rebuilt it with a Turbo Action kit, swapped the stock 1st gear for the 2.74. added a manual VB (Also TA) and ran it for 4 years on the street daily (only transportation I had at the time) and made numerous trips to Atco where I ran Heavy eliminator. Probably 100+ runs with slicks + 100 without. Still worked as good as new when I sold the car to my Nephew. Don't know what the exact HP of the motor was, but it did high 12's @ 109 w/o the 100 shot nitrous I had on it for a month. The tranny in my 416 has been in there for 2 years now and still works like new. I'm thinking it will prolly be pretty ard to break one with a 318 as long as it doesn't have a blower and nitrous.  
 

[Road_Runner]

Thanks guys, looks like there's no reason to rush towards a 727 and given my modest (at least for now) plans for the Barracuda, the 904 should be fine.  Right now its leaking from at least the pan and the rear seal so I'm planning on adding a deep pan and new pan & rear seals to hopefully plug the gaps for now.  If it needs more than that I may just find a good rebuilder.  Anyone know of one in the Atlanta / North Georgia area? 

Thanks again, Jim

[tactransman]

If you had a 727 and a 904,I would definitely say build the 727 since the cost is the same. If you have just the 904 ,it will be fine. Put a Transgo shift kit in it.

[tactransman]

I wish they would have run the 904 in the Challenger,and then stuck the rollerized 727 in the Challenger and compared. That would have been an interesting test to see if a rollerized 727 would ET the same as a stock "low gear" 904.

[71chally416]

If the 727 was as quick as the 904 then there would be no reason whatsoever for every fast NHRA small block car to be running the 904. 

[Road_Runner]

If you had a 727 and a 904,I would definitely say build the 727 since the cost is the same. If you have just the 904 ,it will be fine. Put a Transgo shift kit in it.

I picked up a B&M Transpak for the 904.  Hopefully, it's as good as the Transgo kit you mentioned.  I've picked up a 340 short block that I'll be building over time to replace the 318.  I'm not going to go wild HP wise, I'm aiming for around 350 HP so hopefully the 904 will hold up behind that much power.

Thanks, Jim

[71chally416]

Maybe these vids will put your mind at ease. Both use 904's.

http://streetwalker.homestead.com/files/8secondSBMope.wmv
http://streetwalker.homestead.com/files/9secondDakota.wmv

[tactransman]

Those "904's" will run you about $4000 to $5000!

[71chally416]

Yep, about what a Powerglide that can handle 1,000 HP costs. A normal 904 with stock hard parts can handle mild street driven small block with ease. I know cause I've did it before and I'm doing it again now with a 540hp 416. 2 years and counting with no broken parts.

Of course there's no guarantee on a bagged out 150,000 mile junkyard 904 holding up if you put it behind a 450 hp motor, but a similar bagged out 727 will fair no better. The more mild the motor is and the lower the compression, the more a 904 will help, especially with the cheap good low gear set. 

[tactransman]

Ok,you got me convinced,I am only building 904's from now on !!!!