Another AOD Conversion Story

Discussion in 'Ranchero Tech Reference & Articles' started by Rockdodger, Oct 7, 2009.

  1. Rockdodger

    Rockdodger In Third Gear

    Messages:
    170
    Location:
    Ariz. Terr.
    Thought I might share what I learned on my recent FMX to AOD coversion on "Lazerust", my 1970 Ford Ranchero.
    1. Having an FMX in the car greatly reduced the cost of the conversion. I didn't have to locate and buy the following parts: Block plate, Flexplate, Neutral safety switch, speedometer cable, crossmember or transmission mount.
    2. The boneyard parts I needed were: 28 spline slip yoke, Six 2 1/4 inch bellhousing bolts, Throttle valve rod and transmission lever, shifter linkage bushing and the first 12-18 inches of the AOD's cooling lines. All of these parts came from the same early 80's LTD with throttle body fuel injection.
    3. Based on advice here and from other internet sources I went looking for a late 80's to early 90's V-8 powered donor car. I found one from a 1988 Mustang 5.0.
    4. New parts required were minor bits and pieces to hook the throttle valve rod up to my motorcraft carburetor.
    5. Modifications required were:
    a. Flipped the transmission selector lever by removing the valve body and pulling out the roll pin. (This is required with either an original column or floor shifter which are both rod-operated. The donor Mustang AOD floor shift was cable-operated and reversed the direction of movement.)
    b. Shortened the throw on my floor shifter by increasing the angles of it's two bends. The Mustang AOD tranny shift lever is shorter than the FMX's which would result in the gear indicator not lining up properly.
    c. Had my driveshaft shortened by a little over 1 inch. This cost me more than the transmission itself, as the driveshaft had to be re-tubed. (Total was $187.) I was told that the ideal depth of the slip yoke would be 3/4 inch from bottoming in the transmission. I gave the driveline shop the measurement from the u-joint centers.
    d. Increased the frame mounting slots on the crossmember by about 1/2 inch. (I think I also reversed the transmission mount.)
    e. Cut off most of the carburetor kick-down lever and bolted what was left to the throttle lever. Mounted a screw and threaded ferrel at 1 1/2 inches from the center of the carburetor linkage pivot point. (Same distance as the donor LTD.) Slipped the end of the throttle valve rod over it and added a washer and nut, which I Lock-tited on. Had to bend the throttle valve rod slighty to clear the firewall. Had my dear wife help me check for full travel without binding. Adjusted the throttle valve lever with just slight pressure at idle. Later verified that throttle valve pressure increases proportionally with amount of throttle applied by using a gauge on the throttle valve port on the passenger side of the transmission.
    f. Fabricated a new shifter rod from 3/8 inch threaded rod and a turnbuckle.
    g. Increased the heighth of my home-made shifter hump. (My truck was originally column-shifted, but I now use a 70 Cougar floorshift.) The AOD takes up most of the room in the driveshaft tunnel. There's barely enough room for the end of the shifter.
    h. I had to remove a clip that routed the speedometer cable along the frame to get it to reach the tranny.
    i. Plumbed the AOD cooling lines into the original lines near the oil pan of the engine. Used 5/16 inch compression fittings to make the connection.
    6. Other pointers: Anticipating clearance issues, I inserted the upper two bellhousting bolts and held them in place with a dab of sealer before I stabbed the tranny. Before installing the tranny I made sure that the torque converter was primed with at least a quart of ATF. It is also very important to ensure that the TC is fully seated and engaged in all the shafts of the tranny. The outer ends of the torque converter studs should be about 1/2 inch INSIDE of the bell-housing. Note that if your old tranny was a c-4 you probably can't re-use the items in Paragraph 1. In his excellent pictorial, Hyrb showed how his headers barely cleared the AOD. He used a cable-operated throttle valve. My rod-operated set-up probably wouldn't clear the headers.
    7. Results: So far, so good. Speedometer appears to be close. 3.00:1 rear end is working pretty well with my stock 351C 2 barrel. (My local roads offer plenty of elevation changes.)
    I'm also pleased that when I let off on the gas in overdrive, the car will slow down going down a gentle slope. I'm still getting used to pulling the shifter into "2" when I want to lockout the overdrive.
     
    Last edited by a moderator: Mar 3, 2010
  2. drlance

    drlance In Fourth Gear

    Messages:
    389
    Location:
    Robinson, IL
    Thank you so much for the above information!!!
    I have been thinking about doing the AOD upgrade and now have a good starting point!!
    Lance
     
  3. john777

    john777 In Overdrive

    Messages:
    553
    Good stuff! I'm going through my FMX to C-4 to AOD conversion now.

    . "Had my driveshaft shortened by a little over 1 inch. This cost me more than the transmission itself, as the driveshaft had to be re-tubed. I was told that the ideal depth of the slip yoke would be 3/4 inch from bottoming in the transmission."

    I think I might have to do the same, how much?
     
  4. Rockdodger

    Rockdodger In Third Gear

    Messages:
    170
    Location:
    Ariz. Terr.
    C-4 is different

    John, If you've got a C-4 in it now, you will probably have to shorten the driveshaft even more than mine had to be. I make a big mistake by bringing the driveline shop a driveshaft that had a decaying rubber cushion between an inner and outer tube. When I got my 28 spline yoke at Pick-a-Part, I should have grabbed a complete standard driveshaft. Cost me an extra hundred Ranchero Buck$ to have mine re-tubed.
     
    Last edited by a moderator: Mar 3, 2010
  5. 5.0 Chero

    5.0 Chero Bahumbug Staff Member

    Messages:
    14,289
    Location:
    Prunetucky California
    Thats actually not too bad mine cost me $145 a few year back to have made and I had both ends but that did include new u joints now that I think about it.
     
  6. john777

    john777 In Overdrive

    Messages:
    553
    I looked at my build sheet from before... the cost to balance my old fmx shaft to the new C4 length was $199....i guess I will see...

    once again, great write up!
     
  7. va2ir

    va2ir In First Gear

    Messages:
    5
    Has anyone done this swap on a 73 Ranchero/torino? I have a 351W with FMX tranny, hopefully I wont have to modify my driveshaft. The 2 trannys are almost the exact same length, so I dont think a new driveshaft will be neccessary. Any comments would be helpful. Thanks.
     
  8. LSChero

    LSChero In Maximum Overdrive PLATINUM MEMBER

    Messages:
    2,562
    Location:
    Area 6 NV
    Early 90s lincoln town car shaft fit my 73 pefect.Used adapter u-joint at 9" diff.Moved transmission crossmember rearward 2 inches.
     
  9. va2ir

    va2ir In First Gear

    Messages:
    5
    Was the early 90's drive shaft from the lincoln longer or shorter than the ranchero driveshaft? Or did you not have the original? What was your original transmission? The AOD and FMX (my AOD is from an 89 Crown Vic) has the longer tailshaft. I measured both trannys and it looks like the AOD is about a 1/4 shorter overall. That's why I think my current original Torino driveshaft will work.

    Thanks for any more info.
     
  10. Stuntdummy

    Stuntdummy In Fourth Gear

    Messages:
    249
    Location:
    Pasadena, CA
    Maybe the 70 is a lot lighter than the 72. I currently have the 3.00:1 rear end with the 5.0 AOD, and it makes all gears underpowered, especially overdrive. I have a 3.70 to put in, but I'm wondering if that's too far in the other direction (and I need to get a U-Joint adaptor for the different sized yoke).
     
  11. LSChero

    LSChero In Maximum Overdrive PLATINUM MEMBER

    Messages:
    2,562
    Location:
    Area 6 NV
    Truck originaly 351C-C4,3.00 rear gear.Donnor 89 5.0-AOD.C-4 shaft was aprox. 1.5 too long.Had drive line shop shorten OE shaft.(125.00) They made it too short and wanted another 80.00 to retube it.Picked up drive shaft out of towncar the was correct lenght.shop installed new u-joints and balanced N/C.Did change rear gear to 3.50 trac-lock,3.25 would be my choice if i do another AOD swap.Good luck,John
     
  12. va2ir

    va2ir In First Gear

    Messages:
    5
    OK, so you changed out your motor and as well. I am keeping my 351W in there. Hopefully I wont need to modify my drive shaft. Thanks
     
  13. Rockdodger

    Rockdodger In Third Gear

    Messages:
    170
    Location:
    Ariz. Terr.
    More on my AOD conversion story

    Since converting to an AOD last summer, I have added a mild cam (Comp Cams XE256H), and a performer manifold with an Edelbrock 600 CFM carb. Since my objective was a smooth idling engine that made decent power and good torque without impacting fuel economy, I'm still very happy with my 3.00 rearend ratio. If cost was no object, I would probably opt for a 3.25 to get off the line a little quicker. If I was a racer, I'd go much lower. Just my opinion. Everyone's car set-up and performance goals are different. My gutless, V-6 powered '05 Dakota has a 3.55 and it is geared way too high for it's AOD tranny.
     
    Last edited by a moderator: Jul 10, 2010
  14. va2ir

    va2ir In First Gear

    Messages:
    5
    Rock, my issues really aren't with getting off the line etc.

    My questions are about installing the AOD in place of the FMX, and if there are any surprises to look out for.

    I ordered the shifter rod linkage kit and TV cable from Lokar, I have the complete AOD with torque converter and slip yoke, my only concern is wether the drive shaft needs to be modified or not.

    My engine is the 351W, performer intake, 625 CFM Carter AFB on top, mustang 351W swap headers - cam is original. Car has plenty of get up and go.

    Thanks.
     
  15. Rockdodger

    Rockdodger In Third Gear

    Messages:
    170
    Location:
    Ariz. Terr.
    Sounds like you are on the right track.

    If you can find the right length driveshaft, you will save a bundle. If you can't it is much cheaper to shorten one that's too long than to re-tube one that's too short.
     

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