Borg Warner M12 for performance

"BW was the major developer, I don't know if Ford just fed them money or had an active part in development." 

Lucas660, those numbers were a great help, direct link straight to the source, just had to wait until the middle of the night to call them.

Anyway, according to the very helpful girl in the tech department the clutches and steels for the M12 and FMX are the same part numbers.

So just for the record the following parts are apparently readily available:

P# 49740 - Red Eagle Friction 0.061"
P# 49742 - Red Eagle Friction 0.080"
P# 49700 - Bronze Friction 0.061" (this is the only thickness available in bronze)

P# 23701 - STD Steel Plates 0.068" (flat plates for front clutch pack)
P# 23703 - STD Steel Plates 0.065" (dished plates for rear clutch pack)
P# 23701K - Kolene Steel Plates 0.068" (flat only)

So hopefully that covers it.

The Alto Red Eagle clutches and Kolene (hardened) steel plates would are probably the most well known brands in the performance transmission world and a few people on here have also suggested using the bronze clutches. Alto also makes the regular steel plates and various other OEM replacement type clutches.

I did enquire with one of the other online vendors and their rebuild kits used Borg Warner clutches, which they said were good quality and would stand up to performance use. I reckon the run of the mill friction materials would have probably improved substantially in both performance and durability in the last 40 odd years.

what affects shift firmness is line pressure

if you can't 'feel it', the line pressure is low

(yes; that's true what the other man said about the 'cupped steels' in the 1-2 clutch- they made that clutch grab softer and they can be replaced with 'flat steels' (used in the other clutch, in OEM applications) & then the clutch pack needs to be re-sorted for the correct clearance as prescribed by the overhaul manuals...)

AMC TSM shows how the throttle cable or vacuum modulator adjustment affects main line pressure.

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Edit here for any other casual reader of this thread:

The old article showing the B&M modifications says the AMC two prong type torque converter engagement is prone to breakage. (due to slack in the engagement or whatever)

This is NOT true. (BALONEY!)

The reason why is this: all that engagement does is drive the oil pump.


Hey! If your engine is turning the wrong direction... you've got more than transmission trouble!

The two prongs only need to withstand the amount of power it takes to drive the oil pump, which is a small amount ...like about 4 to 10 hp, estimating 1 hp per every 10 psi -similar to what it takes to drive the oil pump in the engine (typically driven by the distributor drive gear through a shaft to the oil pump)

Moreover, the B&M 'AMC Borg Warner hop up' article shows the FMX torque converter hub and says its stronger... Rather it's the opposite: the two machined flat surfaces that are intended to engage and drive the transmission's oil pump ring gear will tend to 'wedge' the oil pump ring apart instead (assuming there is a 'heavily loaded' condition, which there is not) So, even though the FMXs' torque converter engagement design is actually weaker, still, there is not enough strain there to worry about = it's basically a 'non-issue' ...whatever...

*There are a few internal component parts that spin in the opposite direction, when the unit is downshifted, to give engine braking (for resistance against engine rotation) The transmission's oil pump however, is not one of them.


Edited by amcenthusiast - Feb/06/2020 at 10:10am

Oops! Someone made (and apparently deleted) a post stating the Ford-O-Matic appeared in 1950, not 1953 as I posted. I checked -- correct!! Actually 1951 model cars, but would have been made in late 1950...  I think the article I have from one of the "science" mags on the BW/Stude/Ford trannys (it's titled "The New Automatics" or something similar) of the 50s is a 52 or 53 issue... may be 51. Haven't looked at it in a while!

https://en.wikipedia.org/wiki/Cruise-O-Matic

This article states that Ford was to buy 50% of their trannys for five years, not ten. Not verified, could be either, but I'm going strictly from memory and may be wrong. Not sure when it started either, but shouldn't have been into the 60s... even 10 years would have ended in 60 or 61 since production started in 50/51.


Edited by farna - Mar/16/2016 at 6:23am