Fordnatics List Archive

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Mail From: Kelly Murray <(email redacted)>


> Dan Jones is almost entirly correct BUT small block C6's DO have ribs on
> the upper part of the trans. I suspect he's thinking of the smallblock
> FMX which has an iron case and alloy bellhousing and no ribs.Useful only
> for light use only.

I've been under the impression that the FMX trans is stronger than the C4.
It certainly was installed in heavier cars and trucks as opposed to the C4.

> The small block C6 is quite rare but very handy if your small block
> makes a bunch of power. I read somewhere that racers prefer a C4 despite
> the strength loss due to the lighter weight of the trans and lighter
> rotating mass= faster ET's.

Defintely the C4 is used by drag racers for small-blocks instead of the FMX.
Is the weight savings that significant? Does anyone know the actual weights
of these different transmissions (with and without a stock converter)?

-Kelly Murray (email redacted) '72 Mustang 460 13.31 @ 104mph

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Mail From: "Dan. Jones" <(email redacted)>


> > Dan Jones is almost entirly correct BUT small block C6's DO have ribs on
> > the upper part of the trans. I suspect he's thinking of the smallblock
> > FMX which has an iron case and alloy bellhousing and no ribs.Useful only
> > for light use only.

No, I'm not confusing the C6 with the FMX. My source for the info on the
ribs was a Ford SVO publication that is consistent with my experience.
However, several list members have taken exception to this (smallblock cases
with ribs, FE without), so there appears to be no hard and fast rule here.
All the 429-460 C6's I've seen have had the ribs (over a foot long, starting
on the bellhousing and ending on the case). I've only messed with one small
block C6 and it had a smooth case. It may have had small ribs, but not the
long ones like the 429/460 cases. I know that sometimes the ribs interfere
with tranmission tunnels during engine and tranny swaps so maybe the ribs
are a function of the body style as well.

> I've been under the impression that the FMX trans is stronger than the C4.
> It certainly was installed in heavier cars and trucks as opposed to the C4.

My Dad seems to think they are a fairly strong transmission (stronger than
a C4, but not as strong as a C6), but I don't know the details. He's got
the inside scoop, since he worked at the Ford plant where they were built.
Next time I talk to him, I'll ask. We've ran them behind modified 351's
with no problems. Shift kits are available and you can have the converters
modified for higher stall.

> > The small block C6 is quite rare but very handy if your small block
> > makes a bunch of power. I read somewhere that racers prefer a C4 despite
> > the strength loss due to the lighter weight of the trans and lighter
> > rotating mass= faster ET's.
>
> Defintely the C4 is used by drag racers for small-blocks instead of the FMX.
> Is the weight savings that significant? Does anyone know the actual weights
> of these different transmissions (with and without a stock converter)?

Over the Christmas holiday, when I did the C4-to-AOD swap in the convertible,
I measured some tranny weights:

AOD (without converter or fluid) - 150 lbs
AOD stock torque converter - 34 lbs
C4 (without converter or fluid) - 110 lbs
C4 torque converter - ? lbs
C6 (without converter or fluid) - 140 lbs
Ford-o-Matic (pre-FMX), cast iron case - 228 lbs

Notes:

- AOD and C4 weights are as measured by me using a standard bath room scale.
- Ford-o-Matic weight is an assembly line weight provided by my Dad.
- C6 weight is from "Engine Swapping Tips and Techniques" which also lists
the C4 at 109 lbs.

Unfortunately, I didn't weigh an FMX. Next time I'm back in Cincinnati
to visit the parental units, I'll weigh one. As I remember, with its iron
case, it's a heavy puppy.
Cheers,
Dan Jones

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Mail From: "STEPHEN H 'STEVIE' GROSSEN" <(email redacted)>


Well, I had a some information to add to this thread, but most of it has
already been covered. Presently I have three transmissions in the
garage, a small block C-6, a big block C-6, and an FMX with a small block
pattern bellhousing. The small C-6 does not have any ribs, the big block
does. The weights listed seem pretty accurate to me. I could lift both
of the C-6 trannys and move them by myself (not far and not for long), but
the FMX was gawd awful heavy.
I have a half dozen mag articles and a few tranny shop manuals I
can dig out and look at if anyone needs a reference. (they didn't list
weights, that I found). Just drop me a note and let me know.

steve
(email redacted)