[Von]

I'm embarrased to ask, but is there a difference in a "big-block" and "small-block" 727 and a "big-block and "small-block" four speed?

[dave-r]

Bell housing is different. Some of the 4-speeds are stronger than others. For the 440s and Hemis I would think. The auto boxes will have lighter piston and clutch springs. Fewer clutch plates.

Other than that I think they are all the same?

[Mike]

good question Von...i have wondered the same thing.

[Von]

so would a four speed that was originaly paired with a 340 bolt up to a big block? what would I have to change?

[dave-r]

I thought I already answered that. The bell housing is different so you need a big block bellhousing to physicaly bolt it up.

Also if the 4-speed is replacing an auto trans you need a manual type crank drilled for a pilot bushing or a auto trans adapter bushing.

I don't know which internal bits would be weaker but chances are nothing would break.

[larryp]

Many of the big block 4 speeds were 18-spline input shaft whereas all of the small block were 23 spline. The physical outside dimensions and configuration of these transmissions is the same, so the differing parts are the clutch bellhousing, clutch assembly, and flywheel.

[dave-r]

Good infomation. Thanks for that.