[Steve Chryssos]

Clearance issue are minimal when switching to an overdrive automatic. We use electronic 4L's (4L60E, 4L80E). Your first decision is pre-electronic or electronic. The pre-electronic stuff includes 2004R and 700R4. Since there's no computer, the pre-electronic transmission swaps are less expensive. We can go back and forth regarding torque capacity (500-600 rear wheel), but you've saved me the trouble. You already have a TH400 and Gear Vendors. At those power levels, I would be inclined to keep my current setup rather than switch over to a 200 or 700 trans. The only reason to switch is if you want the benefits of computer control. The only thing you will be lacking is lock up control.

Many enthusiasts are dismissive about electronic transmission controllers. I hear and see it all the time. "Why would I run an E trans? I HAVE to run a computer?" Answer? The computer isn't a necessary evil, it has benefits. A throttle position sensor is way more sensitive and accurate than a TV cable or vacuum modulator. Ditto for a vehicle speed sensor when compared to an old school governor. Reliability is generally improved.

Best of all, an electronic trans gives you control over when and how hard the transmission shifts as well as lock up clutch timing. You also have the ability to add our paddle shifter for full manual control over shifting. But that's icing on the cake. The most important benefit of an e-trans is tuning. You will be able to quickly and easily customize the calibration to your exact vehicle specs and driving preferences.

600 rear wheel is borderline for a 4L60 series trans depending on your intended usage. I would need to hear detailed engine and vehicle specs as well as details on intended vehicle usage to make a determination between 60 or 80 series.