904 for small block

[money pit]

I plan on putting a 318 or 360 in my 70 barracuda. Will a small block 904 trans work for a daily driver? I currently have a slant six with a 904, it runs great. I read a lot of the threads, which say to go with a 727. Any recommendations.  Thanks

[70chall440]

Well I do know you can make a 904 pretty stout and many have been used in race cars. I think the conventional thought is that the 727 is a better trans overall however.

[redo1973]

I've heard the same.  It depends on what you plan to do.  I'm not a drive train expert but put my 904 behind a mild build 340 with intended use of cruises and an occasional straight line but nothing regular. We did a truck shift kit in the rebuild.  I'm still breaking the car in but it shifts nicely so far.  Others on this forum told me that it would be good for up to 400 hp and they are used in racing for the light weight feature versus the 727.

[1 Wild R/T]

904's actually have significant advantages over a 727....  You can get different gear sets... The early 904's were similar to the 727 ratios (1st 2.45, 2nd 1.45 & D 1.0)  but in the late 70's I think around 78 they changed to  First gear: 2.74 Second gear: 1.54 Third gear: 1.00...  The wider ratios allow better acceleration with taller axle gears...

Also the drum that's known to explode in a 727 if you try to launch after a sprag failure? Well the 904 do to it's smaller size & less rotating mass doesn't explode....

Oh, the reduced mass also means less wasted power....   

However 904's are known to have convertor hub failures...

https://www.turboaction.com/technicaltips6.html


Edited  spell check changed sprag to spray.... I changed it back....

[redo1973]

Great info and link.  I'm using an A904 assembled in August 1972.  We didn't change the gears and it was originally behind a stock 318.

[money pit]

Thanks, great info.