904 to 727 upgrade.

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MOPARFIVE

MOPARFIVE

Midwest Moparz
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Hey gang upgrading my 74 Dart Swinger to a 727. Car will have an 8.25 rear. What are the things that need changed to accept new trans? I'm thinking front yolk, driveshaft length, and transmission mount. Can you purchase the driveshaft already made for this combo? Please let me know and Happy New Year!
 
in my opinion going to a 727 from a 904 is not an upgrade . upgrade the 904 to handle your power needs . they can easily be built to handle big hp .
 
jimjimjimmy said:
in my opinion going to a 727 from a 904 is not an upgrade . upgrade the 904 to handle your power needs . they can easily be built to handle big hp .
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Thanks but I have a 727 tci street fighter new in the box that came with the car. No sense in building the 904 in this case
 
MOPARFIVE said:
Thanks but I have a 727 tci street fighter new in the box that came with the car. No sense in building the 904 in this case
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Good luck with that the Total Crap Incorporated trans. I had lasted about 1 week they're garbage!!
 
Only change is shorten the drive shaft and kickdown linkage if I remember correctly. Exhaust may be close because of the larger 727. I run a 727 in everything but an early A. Good luck!
 
Shift lever on the trans may need to be switched out/modified depending what you have (there were different lengths and linkage attachment methods dependent on year and application), but you should be able to make the rest of the linkages work. The slip yoke and driveshaft are different as you mentioned; d.s. length should be the same as for a 727/8.75 combo, but not sure which size u-joint your 8.25 takes. Trans mount is the same.
 
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Don't forget the torque converter and the torque converter inspection cover, I think the dip stick is different too. Might as well install a new starter while you are in this far. This is a really easy swap
 
Total waste of time and money. Keep the 904. I put a 904 behind a 408 Six Pack motor. But hey what do I know? :)
 
You need a shorter driveshaft and the larger yoke for the 727. The shift shaft and kickdown is all in the same location so that can stay the same. Trans mount is the same.
Not cheap but I bought my last shaft from dennys driveshaft. They have a form you fill out with all the measurments they ask for and they build it. Dennys Driveshaft and Driveline Parts High Speed High RPM Balanced Steel and Aluminum Drive Shaft Specialist with Free Shipping on parts orders over $99.00
Check out mancini racing, they also have driveshafts at various price points. Another option, since you need a shorter shaft is to have a driveline shop shorten yours.
904 vs 727 debate. Yes there are plus and minus for each so it really depends on what your doing with it. Race guys like 904 because of less rotating mass to eat horsepower. For durability you cant argue with the extra clutch surface of the 727. I like 727's but I wont build one without a bolt in sprag since I had a sprag failure. I lucked out but from what I hear it is rare for a 904 to grenade the front drum with a sprag failure. Its quite common on the 727 and it aint pretty. So there's that argument too.
For our lightweight A bodys the 904 should be more than sufficient.
 
Built PROPERLY the 904 can handle ANYTHING you put in front of it!!!
 
If by "properly" you mean "high performance" ...I've seen them advertised for $5,000. But any yayhoo can throw a 727 together to withstand 400 horse. So, sure, If you can find a five plate direct drum trans and convert it to non lock up, buy red eagle clutches and a few other goodies, assemble it yourself without overlooking anything..still can't withstand 450 horse daily driving...still not nearly as strong as a stock 727. Just compare a 904 plate to a 727 plate and the HUGE difference becomes extremely obvious. Whereas a 727 can hold 1,000 horse with that same investment. Just with Red Eagles and a thin direct top plate with six reds in there; kevlar bands...
 
CudaFactHackJob said:
If by "properly" you mean "high performance" ...I've seen them advertised for $5,000. But any yayhoo can throw a 727 together to withstand 400 horse. So, sure, If you can find a five plate direct drum trans and convert it to non lock up, buy red eagle clutches and a few other goodies, assemble it yourself without overlooking anything..still can't withstand 450 horse daily driving...still not nearly as strong as a stock 727. Just compare a 904 plate to a 727 plate and the HUGE difference becomes extremely obvious. Whereas a 727 can hold 1,000 horse with that same investment. Just with Red Eagles and a thin direct top plate with six reds in there; kevlar bands...
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Seriously??..my current 904 cost me $500 in parts plus a Ultimate converter at a cost of $500 to build so $1000.00..!!!
 
CudaFactHackJob said:
If by "properly" you mean "high performance" ...I've seen them advertised for $5,000. But any yayhoo can throw a 727 together to withstand 400 horse. So, sure, If you can find a five plate direct drum trans and convert it to non lock up, buy red eagle clutches and a few other goodies, assemble it yourself without overlooking anything..still can't withstand 450 horse daily driving...still not nearly as strong as a stock 727. Just compare a 904 plate to a 727 plate and the HUGE difference becomes extremely obvious. Whereas a 727 can hold 1,000 horse with that same investment. Just with Red Eagles and a thin direct top plate with six reds in there; kevlar bands...
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I have to agree with you. With most small blocks, you don't even need to build a 727. Just replace the seals, filter and fluid, adjust the bands and kickdown, get a good converter and enjoy.
 
If you want a 727 put it in, 727 yoke, shortened driveshaft, torque converter and linkage/trans lines.
 
Its been pretty well covered. You'll need a 727 converter, possibly a flexplate, dust shield, new/modified cooler lines, yoke, have your existing driveshaft shortened locally. It cost me under $100 to have mine done with new u joints and balanced. Its an easy and straightforward swap.


Now the bad news... I would run like hell from that TCI trans. I had a trans built by a well known mopar builder. He swears by TCI parts (he is a dealer and gets discounts) and put a TCI clutch/seal kit, and a TCI valvebody in. That trans made it about 20 miles and destroyed itself. He rebuilt it again under warranty. It made it about 5 miles and started dragging, bogging, not shifting, etc. He refused to do anything about it.

I pulled the trans out and rebuilt it myself in my garage without any fancy tools. I instantly had issues with the trans. So I pulled the valvebody out and swapped in a Cope valvebody. I havent had one single issue since. That trans has taken plenty of street abuse and several 1/4 mile passes at mid 11's. I still have the $400 TCI valvebody in my garage. Its absolute JUNK. It somehow someway was slowly leaking fluid and engaging the low/reverse band while in high gear.
 
pishta said:
Maybe a warped valve body. Easy to check, just split it and put 'em on the glass.....
Dailymotion Video Player - Sir Mix A Lot - Put 'em on the Glass
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Possibly. I used a straight edge to check it and it seemed alright. I pulled it apart to clean it out when I built it and compared some of the mods to a transgo instruction sheet I had. TCI did a few extra mods to the valvebody compare to transgo.

TCI should have checked for a warped valvebody when they modified it. Especially for the 400-450 dollar pricetag!
 
66fs said:
I have to agree with you. With most small blocks, you don't even need to build a 727. Just replace the seals, filter and fluid, adjust the bands and kickdown, get a good converter and enjoy.
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If you choose the best version late 80s lockup version, it has all the heavy duty steel 4 pinion planetaries.Find a slant 6 trans for the input shaft and forward clutch to convert to non lockup and it will hold up very well. Your likely to break that 8 1/4 rear end before you break the 904.
 
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