727 vs 904

[borlaexu7]

What is the difference internally between the 727 and 904 besides the tail shaft lengths?

 

[waggin]

45 hp. to drive the 727...15 hp. to drive the 904.904 takes a longer driveshaft.

 

[autopar3000]

45 hp. to drive the 727...15 hp. to drive the 904.904 takes a longer driveshaft.

Does a 727 really use that much? I've always known it's a bit of a pig that way, but 3 times a 904??

 

[MopaR&D]

It's not really a specific number, more a rough percentage of the HP at the crank is lost to the trans. The 727's absorb more power, but they also handle more of it (at least in stock form) than the 904. The 904 is basically a downsized 727, the design is pretty much the same, just smaller.

 

[moper]

They are remarkably similar... The case and pump are smaller, as are all the geartrain parts. They are just smaller. It's not "over built". Mopar has always had the best, and simplest auto trannys. They are so alike, that they can share valve bodys even tho the internals are different in scale. The specs I remember are on the order of what was posted... I think it was the 904 is a lot lighter, on the order of 30lbs, and takes 27hp less to drive. The surface area is much less on clutches and bands, and the high gear clutch piston uses a single coil return spring instead of multiple return springs. The spring can unwind at high rpm from centrifical force.

 

[goldduster360]

I went with the 999 version of the 904 it had a larger low reverse band and more clutch frictions. It also has a lower first gear ratio 2:74 vs the 727's 2:54. Mine has been behind a mild 360 for ten years, still working great.

 

[mikedevore]

They are remarkably similar... The case and pump are smaller, as are all the geartrain parts. They are just smaller. It's not "over built". Mopar has always had the best, and simplest auto trannys. They are so alike, that they can share valve bodys even tho the internals are different in scale. The specs I remember are on the order of what was posted... I think it was the 904 is a lot lighter, on the order of 30lbs, and takes 27hp less to drive. The surface area is much less on clutches and bands, and the high gear clutch piston uses a single coil return spring instead of multiple return springs. The spring can unwind at high rpm from centrifical force.

YEA, THE NUMBER FOR ROTATING WEIGHT WAS 30 LBS. I HEARD.

 

[LXguy]

YEA, THE NUMBER FOR ROTATING WEIGHT WAS 30 LBS. I HEARD.

the high gear clutch piston uses a single coil return spring instead of multiple return springs. The spring can unwind at high rpm from centrifical force.

A&A makes a kit for the 904 to convert to the multiple return springs. Its cheap and pretty bling too. The sprag in the 904 (stock) is better set up than the 727.

I'm betting on the 904 myself. Less weight to turn, and less weight to carry down the track is what sold me.

A lot of the parts in the 904 are bigger than the Ford C-4, and I've put more horsepower through those than most people are likely to make, so I'm not worried about it. The C4 doesn't have the sprag issues the torqueflite design has, but I don't know how much difference that makes.

We'll soon see.....

Steve