Quote:
Originally Posted by cosmick
...Having the straight-6 engine is no help because those have really poor fuel distribution, so they have to run rich enough so no cylinder ever runs lean...Converting to port injection would really help, but from a practical aspect, swapping vans looks best.
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LOL I have port injection already. 1 injector per cylinder, aimed directly at the back of each intake valve, fuel distribution not an issue. The 4.9L came that way from 1987-96.
The only efficiency gain from an AOD swap would be the lock-up torque converter. It's a weaker transmission and not well suited to vans. It's .67:1 overdrive is a poor mix with heavy vehicles. Driving at my engine's torque peak of 2000 rpm puts me at 56mph now, the AOD would raise speed to 83mph and the 3.27:1 you suggest would only drop it to 78 mph. It would require jumping to 4.10 axle gears to get 2000rpm to be usable (62mph) but those gears would be drastically less efficient at all other speeds. Anything above 60 or so mph is noticeably more work for this big box.
Your cost estimations are also horrendously low. A used trans aint $75 ($109.99 + 29.99 core) and it aint worth the labor to R&R a used unit twice. Gears might be $60 for you ($79.98 + 5.98 core for me) but an axle rebuild kit and the gear swap labor would be $250 easy. I can rebuild my C6 for about $300 and it's pretty darn easy. The much more complicated AOD is about $700 and way more work. IF my trans ever dies I'll rebuild it and replace original thrust washers with roller bearings to gain efficiency but barring that I plan no transmission swapping or mods other than temperature instrumentation and a deeper pan (from a 4wd F350) at the next filter change.