Transmission swap in an 83 f100 flareside question

I have an 83 F100 flareside that I'm making changes to. There is a 351 Cleveland 2v under the hood. This engine is about to get a make over with a bigger cam, aluminum heads, a air gap intake and a 4 barrel (probably the Quick Fuel SS 750.) I'm running dual exhaust from a pair of Sanderson headers. There is a 9 inch in the rear. I am looking to get near 500 horses from the engine as well as neck snapping torque. I cannot stand the thought that a Hemi Challenger might be able to smoke me. As it sits now, there is an old worn out FMX hooked up to the engine. It as seen better days and I do not believe it would be worth rebuilding. My question is what would fit without having to swap or cut the drive shaft. I have been looking through a number of forums but, no definitive answer. I know that the bolt patterns on the C4 and C6 will mat to the Cleveland and same with the AOD. I'd rather have the AOD for highway cruising. Has anyone ever done this swap? If so, what should I be looking to do to make it work?

I've not swapped an FMX to anything, so I don't know.  But we have a page (Documentation/Driveline/Drivehshafts) via which you can probably figure that out.  Unfortunately my internet connection is down at the moment due to quite a lightning storm and I'm just using the cell phone to access the site so I can't check it out.

But if you start with the Application tab and find your truck with an FMX and get the driveshaft # and then with an AOD, you can then go to the Cross Reference tab and look up those driveshafts and get the lengths.

And, if I remember correctly the same crossmember works, but I'm not sure of that.

Thank you!

Just a few things I have learned over the years, The FMX was the performance trans that was put behind the 351 C/M and the 400 in the Torinos and Mustangs. I have a 351C and it was attached to a FMX when I pulled it out of a 73 mach 1 Mustang and put in my 62 flair side. When that went bad, everyone told me to change it to a C6 so I did. What I found out was that the gears in a C6 are lower then they are in an FMX. I went from 3500 rpm at 65 to 4100, Yep, it still has the 5.88 gears in the rear end as it started life with a 240 Inline 6 and a three on the tree. In my infanant wisdom at the ripe old age of 17 I also put USS, 5 slot mags on it with 255/50 15 tires and 245/60 15's on the front( the 351c was put in in 1977 or 78). In the last few years I started a search for an AOD trans and the thought of putting 3.55 gears in the rear end. From what I have been reading and talking to the local trans shops, the AOD wont hold up to a 400+ horse engine. I have been told that I should have kept the FMX and put 3.08's in the rear end.

With all of this in mind, I am going to have the C6 rebuilt and add a overdrive, gear vinders  or some other brand and put the 3.55's in the rear. That way I dont loose the performance and will still have the OD for cruseing at hiway speed.

I am hoping that you have gleaned some usefull information from my long winded story. Unfortunatly the pickup has been sitting for 15 years or so and as soon as I finish my Bronco it is next on the list for a re do

Good info, Steve.

My issues with the C6 are the fact that it doesn't have an overdrive and doesn't have a lock-up torque converter - both of which the AOD has.  But you are right that the AOD can be less than robust.  However Monster Transmissions markets several AODs, one of which is supposed to be good to "up to 600 HP".  On the other hand, I don't know if that comes with a warranty.  Nor do I know how harshly it shifts.

And while placing an OD behind a C6 solves the OD problem I think it exacerbates the slipping torque converter.  My limited understanding of the hydraulics involved in TQs says that the slippage goes up as the RPM comes down, and really takes off as you approach "stall speed".  So as you drop the RPM with the OD but are still requiring the same torque through the driveline to power the vehicle you'll increase the slippage of the TQ.  And all of that slippage gets turned into heat, which can damage the tranny if not cooled, and detracts from the economy as it used to be in the form of gasoline.

To solve all of those problems, meaning the lack of strength of a factory-built AOD and the lack of both OD and lock-up TQ in the C6, Ford designed the E4OD.  And with the upgrades to it over time my understanding is that it does solve all of those problems.  But, it requires some form of electronic control.

Basically, you have to map your way through all of the issues and pick your poison.  Which means the "decider" needs to understand all the issues, which is why we are posting.   

Good info. My old 68 Ranger had a C6 behind the 390. Awful gas mileage. But then I wasn't looking for mileage as I bored it out .30 over and stabbed it with a huge lopey cam among other things only a gear head would do. With this truck, I am still looking for big horses and torque but, highway drive-ability. I have my sights on the TCI Streetfighter AOD. I ran a TCI TH350 streetfighter behind a 355 in the El Camino. The 355 showed near 450lbs of torque and just under 500 horses on the dyno. I still have the car and transmission (car can be seen in the background in the picture of the truck.) Lost the engine some years back due to being so cheap I didn't want to spend $75.00 on screw in rocker studs as I was saving up for a set of Dart heads. Going against the advice of Ron Besselman of Bessel Motorsports/Strokerkits.com (he machined the block) to replace the studs I opt to stay with the pressed in as I had no problem while they were on a 383 stroker in my old 57 chevy drag car. Long story short, the bigger cam in the 355 popped a stud and allowed the rocker to come off of the valve stem and onto the spring retainer. When the cam came around the spring was compressed and threw the keepers. Sucked the valve into the cylinder and out through the side of the block. Expensive lessons suck, literally. Anyway, I was very happy with the TCI transmission.
I'm just not so sure how all of this will go together without making some radical changes such as drive shaft, cross member and, anything else that might need to be done. Whatever it takes, I guess, as I have my sights on those damn Hemis, LOL.
There's just not a lot of info that I can find on putting an AOD onto a 351c in a 1983 F100. I'll figure it out. When I get the chance I'll roll on down the road to Hillbilly Hotrodz as he is just around the bend from me. I need for him to bend and run the pipes from the headers to the back. Check out his Fiat https://www.facebook.com/HillBillyHotRodz-154030678028887/ 

My351 C is no where near stock also, 0.30 over wisco flattops, 11-1, Iski cam, 1.7 to 1 roller rockers on 3/8 studs and gerdles, double valve springs ballanced forged steel crank and eagle rods, all ballanced. The heads are ported and pollished. Accel duel point distrubiter and a flame thrower coil. It gets air through an Holley 650 double pumper and an offenhauser 360 intake. It has headman headers and 3 inch pipes all the way back to the Thrush Hush mufflers. I orignaly got this engine and built it to put in a super stock( read limited late model ) and somehow it ended up in my pickup.

I was told by a sage old trans guy that( after he smacked me on the back of the head and called me a few choice names) that the FMX had a lock up converter in it and you could get after market converters that had different lockup rpm's for different applacations

Old55pete, did your Cleveland start out as a 2v or 4v? Reason I am asking is that from what I've learned over the years is that one can build the 2v using the 2v heads and an after market intake that is designed to match the 2v heads. However, the aftermarket aluminum heads of different brands such as Trick Flow or Edelbrock, as I understand, would be the better choice over the iron heads. You can definitely can massive power from a 2v with the right components. But then, after all is said and done, it's no longer a 2v.
The FMX that is currently in the truck has bad habits. Sometimes it will not move while trying to take off. It will stall while driving. I've swapped out the modulator, to no avail. It has the proper amount of fluid and a newer filter. I'm thinking that the clutches are just worn out. So, instead of spending a ton of cash on rebuilding it, I should do the smart thing and spend a ton of cash on a AOD. I'm pretty sure what I'll save on gas will justify doing this (this is what I am telling myself as I push forward towards spending money on things I really don't need.) Also, the AOD is, from what I can find, about 15lbs lighter. That alone is selling point along with lower RPM highway cruising. Looking to shave weight where ever I can.    

My 351 started life as a 4V, Thinking back to the 77 or 78, I think it had a Carter AFB on it. We used to call them the toilet bowl. Looking down the throat while hitting the throttle and the gas flowing through it looked like you were flushing a toilet.

As for your FMX, mine was doing about the same thing. After I had already put the C6 in it and a few years later, A long story about spending 22 years in the Army................ I was told that the trans it's self was proubly fine but it sounded like the torque converter was failing. I dont remember all of it, but something about the lockup and a spring in a check valve in the valve body. Again, that was in the early to mid 90's  

I am now thinking like you.....I might want to look into an aftermarket AOD trans. The problem with that is convencing the wife that we have enough cubic inches in the check book for that swap.

The Carter AFB is a great carb. Edelbrock bought the rights to them, I believe when Carter went out of business. I had an uncle who was an engineer at Carter in St. Louis. He retired from there in the mid 70's.

I thought about trying a few things, just to keep it moveable but, don't really want to waste time and money on something that I'm just going to replace in the end.

Do you still have those U.S. slotted mags? I had the same mags on all 4 corners of a 1967 Chevy van back in the 70's and on a 71 Duster 340. U.S. mags is still in business. Those slots are right up there with the Crager SS mags.

The Aluminum Four Barrel was a great carb, but the Air Valve Secondary was better.  The ability to adjust the the opening of the secondaries with an allen wrench and a small screwdriver was magic compared to grinding weight off or welding it on after disassembling the whole carb.

A 1971 Duster 340 ran good!  I remember one hanging with my '69 Bee quite well.  (And, by the way, the 383 on my Bee had an AVS, not a Holley.  Long story if you are interested.)

I took that picture yesterday morning, so yes, I still have the mags and I have been offered a lot of money for them over the last few years.

Yea, the carter was a good carb, but a pain in the a..........butt to rebuild. You could rejet the holley at the track in a matter of minutes. Thats why I run them.

Gary, the AVS is a blast from the past and a whole lot better then the thermoquad carb that replaced it.