I was looking to replace my 4L60E for something else as it is about to go on me. I was wondering what you all recommend for a replacement, (TH400, TH200-4R, PowereGlide, etc.) I am looking to put a turbo in it, so I need something strong yet Fuel Efficient.
Since you mention fuel efficient would that mean that you do a lot of street driving? If that's the case I would look into a 4l80e. There's a decent number of people now who have done the swap. 4 gears with 4th being overdrive...as strong as a TH400...can run manual valve body where you shift it all the time or via the computer where the computer does the shifting. (Search in this forum for 4l80e and you'll get some hits on doing the swap.)
The other option would be a TH400 but personally I wouldn't want to go that route if you're doing a decent amount of street driving. Just a TH400 unit I belive will price out cheaper than a 4l80e but you won't have overdrive. If you add the overdrive unit, it will price out about the same or maybe a little bit more. The overdrive unit would add an overdrive to every gear (3 gears plus overdrive on each.) I belive the TH400 is a little lighter than a 4l80e if you're concerned about weight. I don't know what kind of weight difference adding the overdrive unit to the TH400 would make.
There's people running TH400 beind turbo's and there's at least 2 people running a 4l80e being turbo's.