Author Topic: swapping a 904 for a 727 info please!  (Read 975 times)

Offline moparmadd077

  • Jr. Member
  • **
  • Posts: 6
swapping a 904 for a 727 info please!
« on: January 27, 2017 - 09:24:35 AM »
i have an opportunity to pick up a build 727 for my 70 cuda. the car currently has the original 904 in it. my question is, what will I need for parts to make the change? is the driveshaft the same? tranny mount? shifting linkage? I am putting the trans behind a 6.1 hemi. I heard 904 are plenty strong but it will cost me more to build it then it would to buy a build 727 and the torque converters are generally cheaper. It would be nice to have both trans as an option. any info or comments regarding the swap are welcome. 




Offline 1 Wild R/T

  • Resident
  • *****
  • Posts: 4594
Re: swapping a 904 for a 727 info please!
« Reply #1 on: January 27, 2017 - 12:23:59 PM »
Driveshaft is definitely different, length & Yoke...  Shift linkage is different but I've heard of guys making it work.... Kickdown linkage doesn't matter, you'll be modifying anyway... Dipstick & tube are different.... Mount is the same... Cooler lines are the same...
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline moparmadd077

  • Jr. Member
  • **
  • Posts: 6
Re: swapping a 904 for a 727 info please!
« Reply #2 on: January 27, 2017 - 01:32:16 PM »
okay thanks. im putting a bigger rear end in anyway so I will have to find another drive shaft. going to put in a 8-3/4. it has a 7-1/4 now.

Offline 1 Wild R/T

  • Resident
  • *****
  • Posts: 4594
Re: swapping a 904 for a 727 info please!
« Reply #3 on: January 27, 2017 - 02:00:14 PM »
Driveshaft wise I typically find a shaft out of a C body donor so it has the big yoke, big u joints & is to long.... Take that to a driveshaft shop with the length it needs to be & they can cut & balance it for you...
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline Katfish

  • Resident
  • *****
  • Posts: 3733
  • 70 Challenger
Re: swapping a 904 for a 727 info please!
« Reply #4 on: January 27, 2017 - 04:38:24 PM »
If you're going to a Gen3 hemi, I'd be thinking about an OD tranny instead of the 727.