69 Coupe de jour 10 Report post Posted October 12, 2006 Hey guys, anyone familiar with the FMX transmission? Mine is running great with one irritation. I'm in third gear by twenty miles an hour. It shifts really quick! Can you change the modulator valve on the side or do something to extend the shift points a little? Share this post Link to post Share on other sites
Spoofty 10 Report post Posted October 12, 2006 I don't know about the FMX but I know on the C4 you can pull the vacuum hose off the moulator valve and put a screwdriver in and adjust it. I've been told not to go more that 3 turns either way. Maybe the FMX is the same? Share this post Link to post Share on other sites
351carlo 10 Report post Posted October 12, 2006 FMX is the exact same. Vacuum modulator right down on the drivers side rear. Few turns with a screw driver, adjust as necessary. Share this post Link to post Share on other sites
bnickel 10,004 Report post Posted October 12, 2006 that's exactly right. another trick is to pull the actuator rod out from behind the modulator and grind off about 1/8" of it. this will give you much crisper shifts as well as being later than stock. my old FMX i had built about several years ago would make you "SEE GOD" when shifting. it had an NOS ford shift kit with the stage 3 option installed, the modulator adjustment and ground actuator rod. the car would chirp the tires at light throttle and shifting from 1st to 2nd at about 20-25 mph and at full throttle it would bark the tires shifting from 2nd to 3rd at about 70 Share this post Link to post Share on other sites
its a mess 10 Report post Posted October 13, 2006 Hate to ruin everones pie but what if turning the modulator adjusting screw dont help then maybe we have a stuck governer,perhaps dirty fluid type F im geussing? Governer internal centrifical pressure building device creates upshift, modulator extenal linkage device vacume operated delays upshift. my understanding of the FMX is limited to the knowing that it is a c-4 in a cast iron case. i have one of each in the shop right now c-4 FMX and a c-6 but enough would love to find out how you fixed it!! Share this post Link to post Share on other sites
bnickel 10,004 Report post Posted October 13, 2006 the FMX shifts very low from the factory, in fact if you aren't paying attention you might miss all the shifts. as for the fmx being a c4 in a cast iron case? not even close. the valve body is 100% different, the input and output shafts are more like a c6, especially the output shaft which uses the same 31 spline yoke as a c6. the fmx is actually a more modern version of the 2 speed ford-o-matic transmission originally made by Borg Warner. the aod is actually based on the fmx architecture and when built right can handle up to 1500hp, the fmx can also extrem amounts of hp which is why was originally installed behind 390's and 410's. when ford came out with the c6 they replaced the fmx with the c6 behind the big blocks but still used it behind almost all 351's, windsor and cleveland, well into the early 80's when it was replaced by the aod. only a few 351c's in passenger car applications ever got the c6, all of them were 4v clevelands and most of those were in mustangs and some torino's. the fmx was also used in truck app's as well for a short time and when ford came out with the 400m the fmx was the first trans to be used behind it in 71 and 72 and was later replaced by the c6 in passenger cars. the fmx is a very heavy duty transmission, more so than a c4 for sure and a lot more complicated than a c4 as well. Share this post Link to post Share on other sites
bnickel 10,004 Report post Posted October 13, 2006 oh and generally when an fmx has governor problems it's most likely because of trash and metal shavings from the pump coming apart and will generally result in the trans shifting late not early, and having erratic shifts or not wanting to shift from 2nd to 3rd at all and sometimes getting stuck in 3rd gear. in extreme cases it can allow the governor to cease functioning and allow the trans to downshift from 3rd to first during WOT, bypassing 2nd gear as it should when the passing gear is engaged. ask me how i know.... Share this post Link to post Share on other sites
69 Coupe de jour 10 Report post Posted October 14, 2006 Well I got under there today, pulled the line off the modulator, put a skinny flat head screwdriver in there, and couldn't feel a thing! Any suggestions? I adjusted my carb using a vacuam gauge and am idling at 21 inches of vacuam. Idles like a charm now Does this sound right to yall? Thanks Randy Share this post Link to post Share on other sites
bnickel 10,004 Report post Posted October 14, 2006 hmmm, it's possible that it still has the original modulator, they weren't adjustable IIRC. 21 inches sounds about right for a stocker. my last motor was pulling about 35-40 at idle with a super mild cam, almost 11:1 compression and the cam was also advanced 4 degrees. it got excellent mileage on the highway averaging 22-24 mpg. too bad i wondowed the block Share this post Link to post Share on other sites
amanaman11 10 Report post Posted August 1, 2010 oh and generally when an fmx has governor problems it's most likely because of trash and metal shavings from the pump coming apart and will generally result in the trans shifting late not early, and having erratic shifts or not wanting to shift from 2nd to 3rd at all and sometimes getting stuck in 3rd gear. in extreme cases it can allow the governor to cease functioning and allow the trans to downshift from 3rd to first during WOT, bypassing 2nd gear as it should when the passing gear is engaged. ask me how i know.... i have a problem like that with my FMX... it rarely goes into 3rd gear and when it does and i stop and continue it it takes a while to get into 3rd again, mostly when i drive for 30 minutes it'll start going into third... your saying it might be the governor...? Share this post Link to post Share on other sites
