Our '71 Mustang was designed to swallow a C6, so there was no problem. The AOD is beefier around the middle than the C4, so it uses up more space in the transmission tunnel. We used a pair of stacked railroad ties underneath each front tire and a pair of tall jackstands under the rear axle housing. Get the car up in the air as high as possible to give yourself some room to maneuver. on Mom's bathroom scale) for the tranny and 34 lbs for the converter, so a transmission jack is recommended. I measured 150 lbs (without fluid or converter. I don't trust the click-type wrenches on the little stuff.ĭespite its aluminum case, the AOD is no lightweight. dropping the pan), I prefer a beam-type torque wrench so I can tell when I'm approaching the desired torque value. Also, when working with small aluminum threads (e.g. Like the C6 and C4, the AOD has an aluminum case so use a never-seize compound on the aluminum threads (e.g. Come to think of it, we've got some extra 3.50:1 gears so maybe I can talk Dad into swapping them in one of these days. The beauty of this swap is that the AOD's 0.67:1 overdrive ratio can make a 3.73:1 ring and pinion act like a cruising 2.50:1 ratio. If better acceleration is the goal, a ring and pinion swap may be in order. We were looking for longer legs and increased fuel economy so we left our rear end gears alone. The first three gears of the AOD and C4 are of similar ratio. On the down-side, the input shaft is weaker than a similarly sized solid one piece design and you lose the torque multiplication effect. This is an attractive feature when using a high stall speed converter, since locking up the converter eliminates the excessive slippage (and attendant heat generation, RPM rise, and increased fuel consumption) associated with such converters. This arrangement is used to bypass the converter torque multiplication in higher gears (60% in third and 100% in overdrive) for better fuel economy. The AOD uses a hollow two piece input shaft (one shaft inside the other) for lock-up purposes and requires a specific torque converter. The AOD transmission and torque converter are a matched pair. Our C4 was the standard tailshaft model (13 1/8") that was used in most applications. There are also extension housing variations among C4's, with a short tailshaft model (6 5/8") used on some pickups and vans. Also, don't confuse the AOD with the AOD-E, which has the rear mount located farther aft and uses an electronic valve body that requires a separate computer (like that available from Baumann Engineering) unless you are using an EEC-IV engine computer). The catalog also indicates the short extension housing AOD was used in all passenger cars except rear wheel drive Lincoln Marks and Continentals (not sure about the Town Cars), 2WD F-150 trucks built after 11/81, and 83-85 E-150 vans. I forgot to measure it but the SVO catalog says it's 10.1" long. The short model is the one that is closest to the C4 in overall length. When purchasing your transmission, be aware that there are two tailshaft lengths used on AOD's. Because of the Christmas holiday, getting all the right pieces was harder than usual, but we managed. The price was right ($150 rebuilt), but we had to come up with all the bits and pieces. However, we used a transmission purchased from a friend of my Dad's who rebuilds transmissions. If you're pulling the AOD from a car, getting all of the related bits (bolts, electrical connector, dipstick tube, converter, yoke, block plate, linkages, levers, shifter, hydraulic fittings, etc.), will make life a lot easier. I've also listed some comparative transmission weights, dimensions, and gear ratios at the end. To give you an idea of what's involved in a swap like this, I've covered my experience with each of these details in the paragraphs below.
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