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Discussion Starter #1
I'm looking to swap my FMX Trans for a C4 ahead of my future motor swap (302 to 351). Can you please tell me if the tailhousing are different lengths requiring a new driveshaft?

Any other problems I may run into? The car is a 302 FMX P/S car now.
 

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What exactly is it you have now, and are trying to do? A 69 Cougar would have come with a 351/FMX, unless someone swapped in the 302.
Why are you planning on getting rid of the FMX? They are a quite strong transmission. This has been well debated on the board...
 

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Don't you mean the whole transmission length?

The two do not share the same yoke.
 

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Discussion Starter #4

I ran some searches thru the forums but was not having much luck findingthreads for a FMX to C4 Swap which I found odd, so its probably me... My VinPlate was for a 351W 2V but either the previous owner or the owner prior to himdid a mediocre restoration in the early 90's, at which time swapped the 302/FMXfrom a 69 Mustang (according to the casting marks).

I'm working on a hefty restomod of the car right now that will ultimately end up with a 408 Stroker and have read the C4's are easier to buildand are ample in the aftermarket for higher HP engines (Not saying the FMX isnot a good trans). The motor swap is still a year or two away and plan to runthe 302 for the time being. However I would like to avoid rebuilding twoTranny's if I don't need to (economics)

Am I off base by wanting to bolt the C4 in now and run the 302 with myexisting driveline knowing I’ll be moving to the 408 in the future?

If you can point me in the direction of the treads I’ll gladly read up.

Thanks Guys, places like this allow me to take on these projects.
 

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I would just build the FMX..Run the 302/C4 until it's time for the swap. Sure the FMX doesn't have the reputation necessarily, but those in the know still run the FMX.
Much like the rationale of the 289/302 being easier to get HP out of than a "W"....That used to be true. It also used to be true that a "C" head was the end all be all of racing engines. Now we have fairly cheap aluminum heads that flow better than any highly worked over iron head..
But, your money,time and effort!
 

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Remember that input torque is the limiting factor for a trans.

You'll have to put some serious money into a C-4 to get it to hold what a reasonable 408 can dish out. My buddy Terry runs a C-4 behind his 306 (and now 347) in his lightweight race car (2700-pound Pinto wagon). The weak link in the C-4 is the stock 3-pinion planetary gearset. He cracked/broke several of those before getting an aftermarket six-pinion planetary - no problems since. Trans also was converted to roller bearings instead of plastic or solid metal thrust washers.



At the other end of the spectrum, his brother Keith has a 460-based engine (466, 484, and now 545-inch!) feeding the same FMX trans his car came with when it was a 351C-2V! Can't be done, you say? - we used a bellhousing from a late '70s 351M/FMX LTD wagon I had... The FMX has only a JC Whitney rebuild kit, a unknown brand shift improver kit that we installed back in high school 35 years ago, and now a special-ordered B&M torque converter. This is that car on an 11.0x pass with the 484. 3600 pounds, too!



The other 750+hp 460-based stroker motors we run at the track are backed with C-6s - because they're nearly indestructible!





Me? I like having an overdrive if the car is going to be street-driven. I have a wide-ratio AOD (mechanically controlled AOD with a 4R70W gearset) behind the 393W in my 4000-pound '89 Crown Vic daily driver/ backup tow car/ sometimes race car.

 
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