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  • Note to self...
    Thanx to 64ValiantConv (Richard) for this info....

    Another plus is that the a500(42rh) has a 1st gear ratio of 2.74/1 and 2nd gear is 1.54/1. That's a 12% gear reduction in first, making a rear axle with a 3.23 behave like a 3.61 and a 3.55 will behave like a 3.98.
    Transmission A-500 904/727
    First 2.74 2.45
    Second 1.54 1.45
    Third 1.00 1.00
    Fourth 0.69 n/a
    Reverse 2.21 2.21
    The 42rh will bolt right up to the 273/318/360 LA small blocks.
    Here's a link to a great article one of the FABO guys sent to me. It covers upgrading from a 727 to the a518, which will be identical in most aspects to the 904/a500 swap.
    Note to self...
    A few notes on the a500:
    The a500(42rh) is the 904 based tranny with overdrive. I believe the 42rh was introduced in 1988, but I recommend getting the 1993/4/5 because the 42rh had a lot of little changes by 1993/4 and the reliability factor went up. The a500 has 2 major versions, the 42rh (1988-1995ish), and the 42re (1995ish and up). You won't use the 42re, it requires a computer (TCM) to control it. Doable, but expensive. You can tell the difference between a 42rh and 42re by the electical connector located by the shifter linkage. The 42rh will have an oblong 3 pin (one hot wire, one ground to control the OD, and one ground to control the lockup torque converter) and the 42re will have a larger round connector with 8 or 9 pins. Some 46rh (larger 727 based)trannys came with 2 pins on the early model (1988-1992?) because they didn't have a lockup converter. To my knowledge, all 42rh's had lockup converters and cam with the 3 pin connector.
    Note to self......
    - Get a 1993/1994 (and some 1995's) a500 (42rh) overdrive transmission. You may want to add some upgraded clutch discs and a few other things if you're going to drive it hard.
    - Modify your transmission tunnel so the larger overdrive rear end of the a500(42rh) will fit in it.
    - Get the PATC PATC 727 to 518 Conversion Kit (Overdrive/Lockup controller) to control these features on the tranny. $85 for the kit, and not hard to install. There's a deluxe kit for $325, you won't need this.
    - Have your drive shaft shortened and balanced (the overdrive tranny is longer than the 904 and requirs the shaft to be shortened).
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