Auto Transmission Question

H

hh3

New Member

Dec 6, 2004

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Concord, Ca

Dec 6, 2004

#1

• Dec 6, 2004

• #1

I'm in the process of rebuilding the 351W in my 69 Mach and I'd like suggestions on a Transmission replacement. It currently has the "weak" stock FMX and I'd like to upgrade. Any suggestion on a "clean" replacement that I can drop in without a lot of other modifications? Thanks, in advance for the help.

 

Max Power

Active Member

Jul 31, 2003

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St Paul

Dec 6, 2004

#2

• Dec 6, 2004

• #2

Probably a C4 would be the easiest. Not sure if you need a new flexplate and crossmember, but all auto 302 Mustangs in 69 came with a C4, so parts should be pretty easy.

 

Stang_1973

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Jul 13, 2001

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San Antonio, Tx.

Dec 6, 2004

#3

• Dec 6, 2004

• #3

I agree the C4 in its stock form can handle about 350 HP easily. If you beef it up it can handle alot more. It is also alot lighter than the FMX or C6 and has less power loss. You can put a shift kit in to make it have nice crisp or hard shifts, or turn it into a full manual. This costs less than converting a A/T car into a manual car.

 

302 coupe

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Mar 2, 2000

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Macon, Ga.

Dec 6, 2004

#4

• Dec 6, 2004

• #4

there's nothing weak about an FMX, they're good trannies. The only problem is the lack of aftermarket support. If you just plan on a mild rebuild, or a shift kit and converter upgrade, the FMX will be just fine. Its heavy, but thats the only real downside. I'd stick with it if I were you. Strengthwise, its between a C4 and a C6, ditto for parasitic loss. Save yourself the hassle of changing parts and stick with it.

 

G

GaPonyFarm

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Dec 7, 2004

#5

• Dec 7, 2004

• #5

I absolutely agree with 302 coupe! There is nothing weak about an FMX and anyone who says different has never owned one and abused it. It is heavier than a C4, but you can race it all day, without worrying about the heat damaging it. Rebuild the FMX... you won't be dissatisified.

 

D

D.Hearne

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Sep 29, 2000

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south louisiana

Dec 7, 2004

#6

• Dec 7, 2004

• #6

I second that, there was nothing weak about the FMX. I've heard numerous cases where for somereason or other they had been run dry to the point where they quit pulling, then refilled and run some more. try that with a C4. As for a C4 handling 350 horses, I've gotta disagree, I had a heavy duty one in a 69 van behind a 200 horse 302 and in the ten years we had it, we had it rebuilt 5 times.

 

H

hh3

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Dec 6, 2004

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Concord, Ca

Dec 7, 2004

#7

• Dec 7, 2004

• #7

Guys, You talked me into it. I just ordered the master rebuild kit and the shift kit for the FMX. Thanks for the input. You probably saved me a lot of pain.

 

rbohm

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Apr 12, 2002

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tucson,az

Dec 7, 2004

#8

• Dec 7, 2004

• #8

D.Hearne said:

I second that, there was nothing weak about the FMX. I've heard numerous cases where for somereason or other they had been run dry to the point where they quit pulling, then refilled and run some more. try that with a C4. As for a C4 handling 350 horses, I've gotta disagree, I had a heavy duty one in a 69 van behind a 200 horse 302 and in the ten years we had it, we had it rebuilt 5 times.

Click to expand...

i also agree witht he fmx being a strong tranny, but heavy.
as far as a C4, i have run one very close to dry, and still was able to tow a car and not have the C4 break. a C4 will handle about 300hp without upgrades and more when properly upgraded. one more thing, the fmx was the basis for the aod which is also a strong, but misunderstood tranny. if you have a 164 tooth flexplate with the right converter bolt pattern you can swap an aod in place real easy.

 

DarkBuddha

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Dec 11, 2001

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Seattle & Tampa

Dec 7, 2004

#9

• Dec 7, 2004

• #9

Well I'm glad other folks chimed in about the FMX being a good tranny... It is heavy, but it's a good performer. It's the evolution of the old original Ford Cruise-omatic, and was used as the basis for the late model AOD & AODE. The FMX is a great performer, stronger tranny than a stock C4 and will hold up as well as a stock C6. The iron belhousing is what makes it heavy, but it also provides better protection should something let go. The only thing that sucks is that it is a serious power robber. Still, if I hadn't upgraded to the AOD, I would've gladly stuck with my FMX forever.

Go FMX!

 

D

D.Hearne

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Sep 29, 2000

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Dec 7, 2004

#10

• Dec 7, 2004

• #10

Iron bellhousing? Where'd you find that antique? Most FMX's Ive seen had aluminum bells, most had aluminum tailshaft housings too. only the main case was always iron.

 

DarkBuddha

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Dec 11, 2001

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Dec 8, 2004

#11

• Dec 8, 2004

• #11

D.Hearne said:

Iron bellhousing? Where'd you find that antique? Most FMX's Ive seen had aluminum bells, most had aluminum tailshaft housings too. only the main case was always iron.

Click to expand...

Damn, I knew that... iron case, not bellhousing. I gots . Damn, imagine how heavy it'd be with a damn iron bellhousing!

 

K

khsmach1

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Dec 19, 2004

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Dallas, TX

Dec 27, 2004

#12

• Dec 27, 2004

• #12

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What if your goal was a 350+hp engine for street/strip purposes? What tranny would be needed for that type of an application?

 

302 coupe

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Mar 2, 2000

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Macon, Ga.

Dec 27, 2004

#13

• Dec 27, 2004

• #13

a C4 would be preferred in that particular scenario. However, if the car already had an FMX, I'd leave it in place as it should hold up fairly well behind a 350 hp engine.

 

D

D.Hearne

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#14

• Dec 27, 2004

• #14

khsmach1 said:

What if your goal was a 350+hp engine for street/strip purposes? What tranny would be needed for that type of an application?

Click to expand...

The FMX was the transmission of choice for Ford behind the 351 Clevelands, think about it. Also was used behind the 390's in the early 60's. I'f you've got one, keep it. If you don't then get a C4, but don't expect it to last forever

 

1

10secgoal

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Dec 1, 2003

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San Diego

Dec 28, 2004

#15

• Dec 28, 2004

• #15

D.Hearne said:

Iron bellhousing? Where'd you find that antique? Most FMX's Ive seen had aluminum bells, most had aluminum tailshaft housings too. only the main case was always iron.

Click to expand...

Mine had an iron one. USE A JACK. Thems sum heavy sons a .......